<3 IMPORTANT QUESTIONS - Please Contribute!
Internal Structure and Properties of Earth:
- continental crust is much lighter than oceanic crust and does not get subducted.
-Is our earth one homogeneous mass or not? If not explain.
No the Earth is not a homogenous mass. The Earth has different layers: Inner core,
Outer Core, Mantle and the Crust. The outer core is liquid, Inner core and Crust are
solid, and the Mantle is believed to be more solid than liquid but has the ability to flow
slowly. Due to differentiation, the heaviest elements settle at the inner core and then a
gradient of less dense materials comprise of the outside layers (from inner core to outer
core to mantle to crust).
-What is the order (inside out) of our Earth’s internal structure?
Inner core, Outer Core, Lower Mantle, Upper Mantle and the Crust.
Inner core [solid, iron], Outer core [liquid], Lower mantle/Mesosphere [stiff plastic],
Asthenosphere [soft plastic], Lithosphere/Crust [solid/rigid]
-What is the Lithosphere? What is the Asthenosphere?
The Lithosphere is the rigid outermost shell of the Earth. The uppermost mantle
together with the crust constitutes the lithosphere. There are two types of lithosphere:
Oceanic (thinner but denser) and Continental (thicker).
The Asthenosphere is the highly viscous, mechanically weak and ductilely-deforming
region of the upper mantle of the Earth. It lies below the lithosphere, at depths between
~80 and ~200 km below the surface. The lithosphere-asthenosphere boundary is usually
referred to as LAB. Asthenosphere is generally solid although some of its regions could
be melted (e.g. below mid-ocean ridge). The lower boundary of the asthenosphere is not
well defined. Seismic waves reach a low velocity zone here, and it is believed that the
rocks here are closer to their melting point; thus forming a crystal-and-liquid slush. This
may represent the area where magma is generated as the rocks here have little strength
and more ability to flow.
-What are the major materials/rock types making up the layers?
o Continental Crust: Granite, sedimentary, volcanic (Silicate rocks)
o Oceanic: basalt over gabbro
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o Mantle: Peridotite
-What are the important boundaries? Where are they located and why?
● Mohorovicic Discontinuity marks the difference between mantle and crust
● “Yellow Line”: boundary between lithosphere and asthenosphere = LVZ (low
velocity zone)
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-What was used to identify the internal structure of our Earth?
Seismic waves. As P waves spread out from an earthquake they disappear at 103
degrees of arc and reappear at 142 degrees of arc on a seismogram. This region
between 103 and 142 degrees, which lacks P waves is called the P-wave shadow zone.
An S-wave shadow zone also exists and is larger than the P-wave zone because
S-waves cannot travel through liquids. Direct S waves are not recorded in the entire
region more than 103 degrees. This implies that the core must have a liquid outer core
and a solid inner core.
-How are meteorites comparable to the composition of some of the parts of our
Earth?
1)Core similar to composition of molten mass of iron meteorite
2) upper mantle + lower mantle also composition of chondritic meteorites (more dense
material separated from lighter material)
-What does Isostasy describe?
Isostasy is a balance or equilibrium of adjacent blocks of brittle crust “floating” on the
upper mantle. Crustal rocks can be thought of as tending to rise or sink gradually until
they are balanced by the weight of displaced mantle rocks. This concept of vertical
movement to reach equilibrium is called isostatic adjustment. Once crustal blocks have
come into isostatic balance, a tall block (a mountain range) extends deep into the
mantle.
-What is a seismic wave and what does generate them?
Seismic waves are waves of energy that travel through the Earth's layers, and are a
result of an earthquake, explosion, or a volcano that imparts low-frequency acoustic
energy.
-Characteristics of seismic waves? Order of seismic waves in a seismogram?
The primary wave will be the first recorded, then secondary and then the surface waves.
Secondary waves cannot pass through liquids.
-What are the different types of seismic waves? Differences between them?
1.
Body Waves – travel through the Earth’s interior, spreading out from the focus in all
directions
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a.
(P) Primary Waves: fast wave, first to be reported, is compressional. Can pass
through solids and liquids. Rock vibration is parallel to transport direction
Think of a slinky movement
b.
(S) Secondary Waves: slower, transverse wave, travels closer to surface, vibrates
rocks perpendicular to the direction of wave propagation. Passes through solids, but not
liquids. (=shear waves)
Think of a shaking a rope attached to a pole or crowds doing the “wave”
2. Surface Waves – travel on Earth’s surface away from the epicenter. They cause the
MOST DAMAGE compared to body waves because they produce more ground
movement (higher amplitude waves) and travel slowly, so they take longer to pass.
a.
Love Waves: are most like S waves that have no vertical displacement. Horizontal
snake-like waves. Do not travel through liquid. These are the waves that tend to knock
buildings off of their foundations and destroy highway bridge supports.
b.
Rayleigh Waves: behave like rolling ocean waves. They cause the ground to move
in an elliptical path opposite the direction the wave passes. This is incredibly destructive
to buildings
-What happens when seismic wave rays pass through the Earth (processes)? How
can we use these characteristics?
● Refraction causes path of body waves (S and P) to curve upward in a low angle to
boundary -> density increases with depth, so speed increases, and thus they
move towards the boundary
● =Amount of refraction depends on density difference
● Exceptions: speed decrease from mantle (stiff plastic) to core (liquid) causing a
backward bend (high angle to boundary) -> creates p wave shadow zone
● P Waves can pass through liquids, S waves can’t
● Use these Wave properties to determine the internal earth structure
○ Look for changes in speed and angle of waves (using Seismograms); these
areas will be areas of differing density/materials
○ Look for S wave patterns; where it stops travelling is liquid (core)
-Generation of the magnetic field? How does it protect us? Reversal and hazard?
● Earth’s rotation is thought to cause currents in the liquid outer core. Those
currents create a magnetic field
● Slow convection currents in the Earth’s molten nickel-iron outer core are believed
to generate that magnetic field
● Protection:
○ The magnetic field of the Earth deflects most of the solar wind which would
normally strip away the ozone layer
● Reversal Hazard: possibly mass extinctions. (Can someone confirm? in the
lecture they said they were protected even during reversal) There is little evidence
of this, however. This is a bunch of BULL...
○ disrupting navigation and satellites
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○ Many different species use the magnetic field for navigation including bees,
whales, pigeons, Emperor penguins, and albatrosses
Hazards:
-Definition of hazards, disaster, catastrophe? Impact on….?
Hazard: natural process which poses threat to human life/property
Disaster: natural event that causes significant damage to life/property
Catastrophe: natural event that kills or injures large numbers of people or causes major
property damage
Catastrophism: Changes of the Earth’s surface features occur in relatively few major
events separated by long periods with little action. “If it can happen, it eventually will”
-How does magnitude change with changing frequency of disasters/hazards?
Magnitude is inversely proportional to frequency… higher magnitude disasters are less
frequent
-Rough idea of possibilities and problems with prediction/mitigation in general?
● Prediction: not very possible, especially if you want to be very specific
● Mitigation: Possible with public education, Land Planning and Government
education/ Preparation, Insurance
● Problematic: People don’t often listen. If they are in danger they underestimate
how much danger they are in.
○ Place that are hazard prone tend to be good spots for building/agricultural
communities, making people want to live there (viewed as infringement of
personal and property rights)
○ Land use restrictions often come too late anyways
○ People often get bare minimum for insurance, so hazards aren’t covered
Hazards from Space/Solar System:
-Define the various space projectiles (roughly: size, speed, composition, where do
they originate from)
o Asteroids – large metallic or rocky objects. 10 m – 1000 km. 15-25 km/s
ASTEROID BELT
o Comets – large icy objects. 100 m – 40 km, or larger, 60-70 km/s
KUIPER BELT
o Meteors – small rocky objects that survive passage through the atmosphere,
terminal velocity (>300 m/s), usually <1kg, but can be up to 200 kg
Of the 50,000 meteorites found on Earth to date, 99.8 percent are believed to have
originated in the asteroid belt.[67] “
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-What does influence the kinetic energy which is transmitted and converted upon
impact of a meteorite/asteroid/comet?
Kinetic energy of incoming object is converted to heat and vaporization of asteroid and
target. Gases in the atmosphere can provide resistance against the flow of the moving
object. It increases with the mass of an object but increases even more with the velocity
of the object. ke=0.5 mv2
-Location and what is the asteroid belt, kuiper belt, oort cloud? What origins from
these locations?
The Asteroid Belt is actually the space between Mars and Jupiter where it consists of
irregularly shaped chunks of debris (asteroids) made out of rock and metal.
The Kuiper Belt is a region of the Solar System beyond the planets, extending from the
orbit of Neptune. It is similar to the asteroid belt but is 200 times as massive. Most Kuiper
Belt objects are composed largely of frozen volatiles such as methane, ammonia and
water. The Kuiper belt is thought to hold short-period comets. This belt is also home to
three dwarf planets and Neptune and Saturn’s Moons are also believed to have
originated from here.
The Oort Cloud is a hypothesized spherical cloud of icy planetesimals very far away from
Earth in the outer reaches of our Solar System. Long-period comets are thought to
originate from here because of the immense distance.
-Difference between: meteoroid, meteor, meteorite
A meteor is the flash of light that we see in the night sky when a small chunk of
interplanetary debris burns up as it passes through our atmosphere. "Meteor" refers to
the flash of light caused by the debris, not the debris itself.
Meteor is white-hot glowing debris ENTERING the atmosphere; those that are <25m
usually are destroyed before impact.
The debris is called a meteoroid. A meteoroid is a piece of interplanetary matter that is
smaller than a kilometer and frequently only millimeters in size. Most meteoroids that
enter the Earth's atmosphere are so small that they vaporize completely and never reach
the planet's surface.
Meteoroid are solid objects moving in interplanetary space that are CONSIDERABLY
SMALLER than an ASTEROID but CONSIDERABLY LARGER than an
ATOM/MOLECULE
If any part of a meteoroid survives the fall through the atmosphere and lands on Earth, it
is called a meteorite. Although the vast majority of meteorites are very small, their size
can range from about a fraction of a gram (the size of a pebble) to 100 kilograms (220
lbs) or more (the size of a huge, life-destroying boulder).
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Meteor and meteroid refer to outside of the atmosphere. Meteorite refers to when it
enters the atmosphere and lands on Earth.
-Where does a comet’s tail point to/away from?
A comet’s tail points away from the sun, in direction of solar winds
-Two types of impact craters? Difference and why do we have two different types?
o Simple impact craters occur when smaller projectiles make an impact, make a
depression, and an elevated rim made of ejected molten rock
o Complex impact craters occur when large things such as comets … typically we
see a multi-ring structure on top of a depression and elevated, also much larger in
size
Tons of energy melts all the rock that is being struck and gravity is
→
involved in the uplift of the central region (which is attempting to return to eql
position)
-Hazards caused by impacts?
·
Fires – fireball or hot ejecta from impact. The large amount of ejected material can
easily start fires.
·
Darkness – heavy smoke/dust in atmosphere in the air.
·
Ozone layer destroyed because of the vapour in the cloud
·
Nitric acid Nitrogen and water react which can lead to Acid rain
·
Shortage of food – All of the surrounding plants and animals die
·
Airburst – Strong winds that can cause a lot of damage
·
Triggers other natural disasters:
o Earthquakes
o Huge tsunami
o Flood Basalt Volcanism
·
Mass Extinction
o Sudden loss of large numbers of life forms
o 5 major extinction events in past 550 Million years
o Geologic periods defined based on appearance/disappearance of groups of
fossils
o Triggered by:
● continental glaciation / deglaciation
● sudden climate change
● major volcanic eruptions
● major asteroid impacts
-Evidence for impacts?
- Iridium – extremely rare element, in meteorites and deep in Earth’s mantle
-
Glass – forms from melting and rapid solidification of the target and projectile
material
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-
Spherules – tiny hollow glass droplets sprayed out during impact
-
Dark sediment layers – elemental carbon soot/charcoal layer
-
Shatter Cones – cone-shaped features with rough striations radiating outward
and downward from the impact site, usually with a tiny pebble at the apex
-Rough idea how often large vs. small impacts can occur
Every day – ~ 100 tons of dust and sand-sized particles ‘rain’ on Earth
Every year – a 6m asteroid collides with Earth, creates a fireball, and burns up
Every 2,000 yrs – a 100m meteoroid hits Earth and causes significant local
damage
Every 10,000 yrs – a 200m asteroid collides with Earth
-Mitigation of impacts? Possible or not?
● Difficult because there is short time between recognition and impact
● Possibilities?
○ Blasting asteroid with nuclear weapon
○ attach rocket to deflect it, so it misses earth
○ Change amount of heat radiated from one side to change orbit?
Internal Structure/Properties of Earth
(more questions)
What do we use seismic tomography for?
Seismic tomography is a technique for imaging Earth’s sub-surface characteristics in an
effort to understand deep geologic structure. Gathering sample compressional wave
(P-wave) and shear wave (S-wave) travel time measurements allows us to compile 3D
images of earth’s velocity structure.
What do the slowed down vs. increased velocities of seismic waves shown in a
seismic tomography map tell us and what did researchers find out based on this?
● velocity changes tell us: lateral variation in wave speed within the shells of the
Earth
● Researchers found Out
○ where density differences are present, and what those density differences
are
○ what the different temperatures of3 those areas are since hot =lower vel,
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cold = faster
Plate tectonics & Plate boundaries:
What does the plate tectonic hypothesis explain? What was suggested by the
former continental drift theory?
The plate tectonics theory describes large-scale motions of Earth’s lithosphere due to
seafloor spreading. Continental drift suggested that the continental rock could flow
through the much denser oceanic crust however, there were no known forces which
were strong enough to do so and so the theory was originally dismissed.
Which of the major layers of our Earth do the tectonic plates belong to?
● Lithosphere
Some evidence for plate tectonic motion?
- Geologic evidence of rock units on different continents with similar structural style
- Fossils found on different continents that would make sense only if Pangaea was fully
connected.
- Evidence of a former glacier would show that the glacial ice moved out from the middle
of the ocean, but glacial ice does not form in the ocean. If the continents fit together like
Pangaea the glacier moved out from the south pole.
How many major (large) tectonic plates do we have?
We have 12.
What are the three different plate boundaries and what happens at the respective
types?
1.
Divergent: Two plates moving away from each other, earthquakes are shallow
and lower magnitude.
a.
If divergent with two oceanic plates you will have a Mid-Oceanic Ridge and a rift
valley found on the ridge crest.
b.
If divergent boundary between continents you will have a rift valley, normal faults,
shallow-focus earthquakes.
2.
Transform: Two plates sliding past each other, faults will form in a strike-slip
motion parallel to the boundary. Often shallow earthquakes.
3.
Convergent: Two plates moving towards each other (colliding).
a.
Collision of two continents results in shallow earthquakes over a complex system
of faults and build mountain ranges.
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b.
Subduction of the ocean floor will result between an oceanic plate and continental
plate. Normal faults often form. Often results in an oceanic trench on the ocean side and
a mountain range on the continental side. Volcanism typically occurs at these plate
boundaries.
c.
Two oceanic plates will lead to one being subducted under the other and typically
create an island arc formed from volcanoes. A deep oceanic trench is located in front of
such arcs where the descending slab dips down.
What type of crust is more likely to be subducted (sinking into/recycled into) the
mantle? And what are the reasons?
The oceanic crust is more likely to be subducted as oceanic plates are more dense than
continental plates.
Features of a subduction zone (at convergent plate boundary)?
● Definition: Subduction zones – where two plates meet, denser (oceanic) plate
slides beneath the other and sinks into mantle
● When oceanic subducts below oceanic → Island/volcanic arcs, volcanoes,
earthquakes
● Oceanic subducts below continental → continental arc, mountain building,
earthquakes, volcanoes
● Continent below continent → mountain building, earthquakes
Example of continent-continent collision, ocean-continent collision, hotspot?
● himalayas→ indian and eurasian plate (continent-continent)
● andes→ nazca and south american plate (ocean-continent)\
● hawaiian island/Emperor chain of volcanoes (hot spot)
What is a hot spot? Where would it form and what can it tell us?
Hotspots are volcanic regions thought to be fed by underlying mantle that is anomalously
hot compared with the mantle anywhere else. They are commonly intraplate occurrences
but can occur at plate boundaries as well. They are thought to be made from hot mantle
plumes that rise from the core-mantle boundary. Tells us absolute plate motion because
the plate slides over the hotspot forming a volcano arc
On which type of plate boundary can new ocean floor be created and why?
Divergent boundaries between two oceanic plates allow for the creation of new ocean
floor at the ridges of MORs (Mid-Oceanic Ridges).
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What does the striped magnetic pattern of the seafloor form and what does it tell
us?
The striped magnetic pattern is due to the new crust being formed at the tip of MORs
and spreading out in either direction. The rocks hold different magnetic patterns at the
times which they formed. This tells us that the rocks will get older and older as we move
farther away from the ridge and also showed us that the Earth has reversed magnetic
polarity at seemingly random intervals.
Paleomagnetism, how does it work (roughly)?
● Paleomagnetics = magnetic dipole in rocks due to convection of outer core
● Paleomagnetism is the process of recording magnetic orientation of rocks (from
sea floor spreading zones) to analyse the date, and behaviour of Earth’s magnetic
field at that time
● The fossils/rocks get their magnetism by: cooling of magma below
curie-temperature
What does continental rifting lead to?
Rifting is the process by which the continental lithosphere stretches. A Continental rift is
the belt or zone of the continental lithosphere where the extensional deformation (rifting)
is occurring. These zones have important consequences and geological features, and if
the rifting is successful, lead to the formation of new ocean basins.
What does sea floor spreading mean?
● the formation of new areas of oceanic crust, which occurs through the upwelling of
magma at midocean ridges and its subsequent outward movement on either side.
What does the term “Wilson cycle” describe ?
● Describes the cycle of Supercontinents breaking up and forming again
How old (roughly) is the oldest (still existing) sea floor in our oceans? What does
increase with distance from a mid-ocean ridge?
● Oldest still existing ocean is roughly 155 million years old (Correct me if I got it
wrong!) isn’t it 180 million? - The PDF says 155, but she could have said
something different in class. I just can’t remember what she said lol.
● The Atlantic Ocean formed about 180 million years ago, so I believe 155
million years old is wrong.
● Age of oceanic lithosphere, thickness of lithosphere and depth of ocean
floor increase with distance from the mid-ocean ridge
Why is the seafloor relatively young?
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The seafloor is relatively young because it is continuously being subducted and oceanic
crust tends to get colder and denser with age thus sinking into the upper mantle.
What is a supercontinent? Maybe an example?
A supercontinent is the assembly of most or all of the Earth’s continental blocks to form a
single large landmass. Pangaea is an example of a supercontinent.
What is an apparent polar wander path and what information does it give us?
An Apparent Polar Wander (APW) is the perceived movement of the Earth’s
paleo-magnetic poles relative to a continent while regarding the continent being
studied as fixed in position. It is very useful in plate tectonics since it can retrace the
relative motion of the continents, as well as the formation and break-up of
supercontinents.
At what plate boundaries (or at which stages) do we find Volcanoes?
● Subduction zones (oceanic-oceanic, continental-oceanic convergent boundaries)
and hot spots
Two methods how to model/detect the shape/angle of the sinking (subducted)
oceanic crust at convergent boundaries?
● 1) Using earthquake records - record earthquakes on subduction zone over time
using seismographs. Can create a record of the earthquakes, see that they are
moving and getting deeper and deeper.
● 2) Using seismographs - record P-wave and S-wave activity from earthquakes.
Use activity to determine the composition of the subduction zone (heat, depth,
etc). Can use these characteristics to determine the shape/angle.
Hazards at plate boundaries?
● All of them! Earthquakes, tsunamis, volcanoes
Why do we have earthquakes/deformation/mountain belt formation at convergent
plate boundaries?
● 2 plates are pushing into one another, the force causes slips of the plates =
earthquakes
● Deformation/Mountain belt: the collision causes thickening of the combined
lithospheres until a mountain range is formed.
Why do we have volcanism at convergent boundaries?
● The plate that subducts below the other plThe hot rock (magma) then becomes
less dense, and riate goes into the mantle and heats up ses through the crust
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● Magma rising at convergent boundaries usually travels up through mountains
created at these boundaries = volcanism
Wadati-Benioff Zone?
● zone of deep earthquakes in subduction zone due to differential motion
● beneath volcanic arc/continental margin, above subduction zones
Why did the Alps and the Himalaya form? Name some characteristics of the
mountain belts? Could these pose a threat to humans?
● Formed because of continental collision zones; collision causes combining of
lithospheres.
● combination makes lithosphere thicker, causes growth of mountains
● Mountain Belt Characteristics
• glaciers on the peaks
• steep + pointy
Location of the most seismic hazards on Earth?
● At plate boundaries
●
Relative vs. absolute plate motion, what is the difference?
● Absolute plate motion = motion with respect to deep mantle
● Relative plate motion is how plates move with respect to one another
Earthquakes:
Define earthquake.
● a sudden and violent shaking of the ground, sometimes causing great destruction,
as a result of movements within the earth's crust or volcanic action.
Where do earthquakes occur in general (a few general examples)?
● Earthquakes generally occur along fault lines, though they may also occur inland.
● Examples: Subduction zones, spreading zones, strike-slip (transform )faults,
normal faults, reverse/thrust faults
What causes earthquakes?
● Earthquakes are caused by movements along fault lines, built up energy due to
elasticity of rocks and subsequent release of this energy.
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How do earthquakes form (term, rough idea about theory)?
● Elastic rebound theory: earthquakes are formed by the build-up and release of
applied forces. 1. Fault is locked, 2. force builds up 3. rocks near fault bend
elastically 4. strength of the fault exceeded 5. fault slips = earthquake 6. elastic
rebound - return to previous state but displaced.
What is a fault and name the 3 general types (difference between them)?
● A fault is a break in the crust or rock where two sides move against each other .
The three general types of faults are
1. Reverse/Thrust Faults: come from compression in the crust. the rocks above
steeply inclined fault surface slip up over the rocks beneath the surface (thrust
faults generally have more gently inclined surfaces)
● 2. Strike Slip Faults: Happens on a vertical surface. Shear Stress. Rocks on one
side of the fault slip laterally past rocks on the other side of the fault. (when rocks
slip on the right it is called a right lateral strike slip fault, and vice versa for the left
side)
● 3. Normal Faults: Occur due to crustal extension. Tensional stress. Rocks above a
steep inclined fault surface slip down over rocks beneath the fault surface.
Name the 3 general ways how a force (arrows) can be applied on the crust or plate
boundaries and general effects on crust?
● Compression > < causes folding, causes denser (or older) crust to subduct under
other crust, reverse/thrust faulting.
● Tension < > causes stretching/thinning, normal faulting.
● Shear V^ causes Shearing, strike-slip faulting
Meaning of terms: epi- vs. hypocenter
● Hypocenter= source of earthquake
● Epicenter = spot on surface directly above hypocenter
What types of seismic waves are generated during an earthquake and what are
their characteristics?
● Body waves:
○ P-waves = primary waves = compression + extension in direction of
propagation. Travel through every medium
○ S-waves = secondary/shear waves = up and down wiggling perpendicular
to propagation direction, No volume change, but shear!, slower than P
waves but quick, can not travel through fluids/gas -> can’t transmit shear
stress that shears material, earthquakes generate larger S than P waves ->
more damage due to strong shaking close to epi-/hypocenter
● Surface waves: (More destructive than body waves)
○ Love waves = sideways wiggle decreasing downward
○ Rayleigh waves = ground roll moves through earth layers like ripples
(perpendicular and opposite direction to wave propagation)
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Characteristics of a seismic wave on a seismogram (terms)
● amplitude, wavelength, and frequency of vibration
How to do we determine earthquake epicenters and travel times (roughly)?
● Use time interval between P wave arrival and S wave arrival on seismogram
approximate distance to earthquake
● Arrival times of P waves and S waves indicate distance but not direction of
earthquake
● Wave arrival times needed from at least three stations to pinpoint location of
earthquake
● Three circles should intersect at one location
How do we define the size/intensity/magnitude of an earthquake and name the
various types of scales?
● Size = offset of fault (movement across fault) and surface rupture length (total
length of break)
● magnitude = amount of energy released
● Intensity = duration, violence
● Scales:
○ Mercalli Intensity scale: assigns value to intensity of the shaking at a
particular site (how many people felt it, subjective value)
○ Richter Magnitude - based on maximum amplitude of earthquake waves
measured on seismogram
○ Moment Magnitude; measures energy release, measure of total energy
expended
○ Environmental Earthquake Effects Scale - uses description of natural
phenomena to assess amount of disturbance,
What is used to determine magnitude by the Richter scale and how does it
increase?
w
- based on direct measurement from seismograph; Wood-Anderson Seismograph
- amplitude 10 times greater on seismograph corresponds to magnitude greater by 1.0
Name some secondary effects and why these occur.
● Fires - electrical wires exposed/damaged during destruction/shaking of a building
● Amplification of shaking - because of loose, soft ground
● Liquefaction - because when shaken, soils become almost liquid. causes damage
to buildings
● Slope failure - surface waves cause rock layers to be disturbed
○ can be: Avalanches, rockslides, mudslides
● Disease - disruption of water mains caused by earthquakes can lead to impure
water
Name some hazards during an earthquake.
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● collapsing buildings and structures (walls, furniture, floors, ceilings)
● Death due to falling objects
● Fires
What mitigation actions can we take to minimize damage etc?
● Forecasting, Assessing seismic risks
● Land Use planning: not building on sites of high risk
● building codes - use more stable materials and methods, have more
foundation/support for structures, increase distances between buildings
What is possible forecast vs. prediction and why?
● Forecast is possible compared to prediction. This is because it is almost
impossible to predict exactly when and where an event will occur. It is possible to
forecast how frequently an event occurs, and where it is most likely to occur.
● Also, prediction causes hysteria, it is costly (especially if prediction is wrong)
Which methods can use to assess seismic risks?
● Studying historic earthquakes, On-going monitoring of earthquake activity
● Geological Studies, determining relative hazards, Seismic hazard maps
Volcanism:
What is magma vs. lava?
Magma is the molten material beneath the Earth’s crust. When magma
reaches the Earth’s surface, it becomes lava.
How does magma form, and what are the main factors enabling magma
generation?
Magma is from a magma chamber beneath the earth’s surface. When pressure is
decreased, or when temperature or water is added, the magma rock melts and
rises to the surface.
-Viscosity (how fluid magma is)
-Its volatiles (the quantity of water vapor and other volcanic gases it contains)
-Its Volume (the type and amount of magma that erupts
What forms when magma reaches the surface?
Lava
Name the various types and most important characteristics.
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Magma Types:
Basalt - is a black or brownish black and its magma is about as fluid as cold
molasses ~50% silica
Rhyolite -comes in white or pale shades of grey, yellow, pink green and lavender
● rhyolite magma is extremely viscous, causing it to flow stiffly
● ~60% silica
Andesite -falls between low-viscosity basalt magmas and high viscosity rhyolite
magmas
● it is the most abundant type, erupting from subduction-zone volcanoes
● ~70% silica
What are the main factors responsible for the differences in eruption style?
Viscosity: how fluid the magma is
Volatiles: the quantity of water vapour and other volcanic gases it contains
Volume: the type and amount of magma
How does a violent eruption differ from a rather quiet eruption (rough idea of
process)?
Magmas that contain little water erupt quietly as lavas; those that contain large
amounts of water are likely to explode.
Also, hotspots under oceanic lithosphere has magma that contains basalt and
have more peaceful eruptions than hotspots under continental lithosphere in
which basalt mixes to form rhyolitic or andesitic magma which explodes,
Name the 3 main types of magma or lava.
● basalt, andesite/dacite, and rhyolite
Define viscosity.
● the state of being thick, sticky, and semifluid in consistency, due to internal friction.
What are the main factors influencing the viscosity of a magma?
-the chemical composition- the internal arrangement of its atoms and molecules
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temperature, volatiles, composition of lava
Where do volcanoes typically form?
-Plate Boundaries (Convergent and Divergent) + Hotspots
-Under Subduction-zones (most common and most hazardous) and at Hot Spots
(least common, produce large amounts of magma)
Which is the most violent, intermediate violent and least violent eruption type?
● Most Violent: Plinian
● Intermediate: Strombolian/Vulcanian
● Least: icelandic
Name some hazards related to volcanoes and why are they hazards?
● Explosive Eruption - hazard because it rains down magma on everything (cause
fires, burns, smoke, etc)
● Lava flows - damages housing and kills people if they get caught in it
● Lahars - Mudflows are quick and hot, will kill everything in their path
● Lateral Blast - explodes laterally, more likely to hit people/buildings
● Fires, Harmful gases, Acid Rain, Earthquakes, Diseases. Tsunamis - enough said
● Ash in Atmosphere - can reflect light, causing drop in temperature
● Tephra - If big enough and blasted far enough can cause damage to buildings,
cars, people
● Pyroclastic density Currents - consist of two parts: a basal flow of coarse
fragments that moves along the ground, and a turbulent cloud of ash that rises
above the basal flow
○ it is extremely hot, kills every living thing in its way
● Landslides/Avalanches: Damage to buildings, roads, people if they’re in the way
Is there a scale for volcanic eruptions and if how are the magnitudes defined?
● Magnitudes defined by Volume of Tephra erupted
● Also defined by height of the vertical column
● Scale goes up by factor of 10 like the Richter Scale
What can we use to try to predict/forecast volcanic eruptions?
● Past volcanic activity (volcano records, Paleovolcanology)
● Short term indications - change in surface temp, laser tiltmeters, change in gas
emissions
Is it really possible to predict vs. forecast volcanic eruptions?
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● No, not possible to predict because even the early warning signs don’t always
mean there is going to be an eruption
● Forecasting more likely because you can say how often the volcano has erupted
in past
Are there any reasonable mitigation measures to minimize or avoid damage/death
due to volcanic eruptions?
● Slow down/Divert magma by cooling it down/trying to solidify it
● warnings and evacuations of populations
● Not building near an active volcano
What are the typical problems of predicting/forecasting/mitigation of volcanic
hazards?
● Problems are: people want to build where they want to build. So land use planning
not always possible. Volcanic soil is good for growing/building, so people want to
build there even if it isn’t safe
● Predictions not possible because we don’t always have full records of activity,
don’t know where hotspot is, etc
● Another problem is people don’t always listen to forecasting/signs
There’s like 2 missing questions down here
Atmosphere/Weather/Climate
Define weather and how is it different from climate?
Weather: short-term conditions of the atmosphere at a particular location
Climate: the average weather for a particular location over a long period of
time (years or decades)--> Usually 30 years
0.93%
●
Layers: Troposphere- first layer above the surface, where most of the
weather takes place.
○ Stratosphere- very stable. Contains 19% of the atmosphere’s
gases and the ozone layer, which absorbs harmful rays from the
sun
○ Mesosphere- where most meteorites burn up.
○ Thermosphere- Hottest layer, high energy rays from the sun are
absorbed
○ Exosphere- molecules from atmosphere escape into space.
Satellites orbit here
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What causes weather?
Different insolation patterns (thus, different pressure areas, wind, heating, etc. = all
lead to different weather patterns).
What is insolation?
Total amount of solar radiation on a given surface area
What is atmosphere?
Layer of gases surrounding Earth held by Earth’s gravity.
Name the variables affecting weather and climate (all factors mentioned so
far in lecture)? Describe origin/meaning of terms and how do they affect
weather?
●
●
●
●
●
●
●
air pressure- caused by weight of air above the measurement point
wind- a natural movement of air of any velocity and horizontal flow of air
air masses- a large body of air that has properties similar to the part of the
earth’s surface over which it develops
humidity- the amount of water vapor present in the air
relative humidity- is a measure of the amount of water vapour present in the
air compared to the amount needed for saturation at the specific temperature
clouds- masses of small water droplets or tiny ice crystals that float in the air
precipitation- water that falls from the clouds (air temp. determines form of
precipitation (rain, sleet, hail, snow))
Describe pressure variations, how are the called, and what do they cause?
- Air pressure: pressure within atmosphere varies both horizontally and
vertically.
- Wind is the horizontal flow of air.
-Air is always moving from high pressure to low pressure
-the strongest winds are tornadoes, the air pressure is extremely low
Can such pressure variations influence our weather/climate locally,
globally, or both?
Both
Describe roughly how the global convection cell-wind system works, and
what does affect it???
Convection patterns (cells) by latitudes, starting at equator with intense
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sunshine powering air circulation patterns!
- Atmospheric circulation: large-scale movement of air by which thermal
energy is distributed on the surface of the Earth (connected to ocean
currents).
- Constant basic climatological structure of atmospheric circulation with
yearly variations
Types of cells:
- Hadley cell: closed circulation loop, which begins at the equator with
warm, moist air rising (Low) to the tropopause and carried poleward.
Descends at about 30°N/S latitude (high), closing the loop of the
Hadley cell and creating the Trade Winds.
- Polar cell: Warm air rises at higher latitudes and moves poleward
through the upper troposphere (north and south poles). When the air
reaches the polar areas, it has cooled and descends as a cold, dry high
pressure area, moving away from the pole along the surface but
twisting westward Polar easterlies.
- Ferrel cell: It behaves much as an atmospheric ball bearing between
the Hadley cell and the Polar cell, and comes about as a result of
the eddy circulations (the high and low pressure areas) of the midlatitudes.
Name the major wind currents on earth.
-Polar Easterlies, Westerlies and Trade Winds
Define the terms and what are the differences between warm, cold,
occluded and stationary weather fronts (roughly)?
Warm Fronts- generally poleward movement, slower, usually preceded by stratiform
precipitation and fog
Cold Fronts- generally west to east movement, faster, thunderstorms and severe
weather
Occluded- the 2 air masses merge and force warm air between them to rise quickly,
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cold front overtakes a warm front and causes strong winds and heavy precipitation
Stationary- When two air masses come together but neither displaces the other, the
boundary between them is referred to as a stationary front. Warm or cold front stops
moving. Light wind and precipitation may occur across the front boundary.
- What does the term Coriolis Effect mean? Describes what it influences and how.
Coriolis Effect: because earth rotates from west to east, large masses of air and water on its surface tend
to lag behind a bit. Water and air move above the planet, which rotates faster under them, they lag
behind the earth’s rotation. Coriolis force is basically, the forced curvature of air or water due to Earth’s
rotation.
○ What it influences and how: In the northern hemisphere, the water and air moving south
(with the earth rotating faster to the east below it), will lag and the lag will cause them to
veer off to the west.
■ As water and air currents moves towards the poles – in this case the air or water
is moving over areas of Earth with slower surface rotation, the resulting lag
causes a curve off to the east.
■ Thus in the northern hemisphere, large currents of air and water curve to the
right (clockwise) and to the left in the southern hemisphere (counterclockwise)
■ Ocean currents move westward as they flow towards the equator and eastward
as they head towards the poles
- What is a jet stream?
Jet streams are fast flowing, narrow air currents found in the atmosphere. The main jet streams
are located near the tropopause, the transition between the troposphere (where temperature
decreases with altitude) and the stratosphere (where temperature increases with altitude). The
major jet streams on Earth are westerly winds (flowing west to east). Their paths typically have a
meandering shape; jet streams may start, stop, split into two or more parts, combine into one
stream, or flow in various directions including the opposite direction of most of the jet. Jet
streams can travel at speeds of 100-400 km/h. Long-distance aircrafts sometimes use jet
streams to save on fuel.
-What are clouds and why/how do they form? Name the some types (e.g., clouds typical
for thunderstorms).
Clouds are a visible mass of water particles, vapour or ice floating in the atmosphere. Water
vapour starts out as a small nucleus (aerosal) that starts the formation of the cloud. The sun
basically heats the air near the surface of the Earth and this rises. As it does, the air and vapour
begin to cool and condense, forming a visible cloud.
Cirrus- Found high in the atmosphere. Thin and wispy, fair/pleasant weather
Cumulus- found in mid-atmosphere
Stratus- found in the low atmosphere. Look like blue/grey fog. Signal storm of continuous
precipitation
Nimbus- Storm clouds. Flat base and fluffy top.
picture below for reference
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- What is Precipitation? How does it form? Name the major types?
Precipitation is when there is too much moisture in the air. The water will fall as precipitation. 2
Main Types: rain & snow
- Name the influencing factor of our weather/climate and describe them roughly.
•Variations in insolation - solar radiation
•Astronomical factors (seasons) - Earth’s orbit and tilt
•Land elevation -caused by plate collision; ^height of land=rain/moisture cannot get over it
(mountains); this causes deserts etc.
•Plate tectonics -collision zones
•Surface albedo -how much solar radiation is reflected back into space. More reflected? Absorb
less on planet so it’s colder…
•Atmospheric factors - ozone layer to keep heat/solar radiation IN… ozone is depleted, more gets
in but more leaves too.
- What does the term Milankovich Cycles stand for?
The change in ellipticity of Earth‘s orbit every 100,000 years
- What does the term Thermohaline circulation stand for?
Thermohaline circulation (THC) or Ocean conveyor belt is a part of the large-scale ocean
circulation that is driven by global density gradients created by surface heat and freshwater
fluxes. The ocean redistributes large amounts of heat around the planet via global ocean
currents - through regional scale upwelling and downwelling.
- How/why does the oceanic circulation work?
Oceanic circulation in the equatorial Pacific Ocean normally flows westward, pushed by the trade
winds. Salt-rich & cold currents sink and travel along the bottom of oceans toward lower latitudes
(south) while less saline currents travel at the surface toward higher latitudes (north).
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- Could the oceanic circulation change over time? And if yes, what could
change it?
Yes, Changes in salinity content of the water from factors such as melting glaciers and ice sheets
can alter the path and strength of circulation. Lower-density fresh water cannot sink into
seawater, so the circulation may slow or stop.
- Does the Coriolis effect affect the small to large scale oceanic circulation? And if yes,
how?
The Coriolis effect strongly affects the large scale oceanic circulation leading to the formation of
jet streams and western boundary currents. Atmospheric pressure systems create strong winds
along the eastern Pacific. Changes in global air temperatures over land and the ocean, as well
as increased temperature variation, will alter atmospheric pressure gradients that drive the
strength of winds. over the ocean. The Coriolis and pressure gradient forces balance each other.
The Coriolis Effect not generally have a big influence on small scale objects at the earth's
surface
- What does the term El Nino stand for? Describe roughly what happens compared to
normal conditions?
El Nino stands for “boy child” in Spanish. When warmer surface water moves eastward in the
equatorial regions of the pacific (where it normally moves westward) showing a reversal in
weather patterns. El Niño results in extreme weather and weather related hazards, but it affects
weather patterns differently around the world. In contrast to rains and floods in western South
America, Mexico, and California, droughts and widespread fires affect Australia, Indonesia, and
Southeast Asia.
Climate and Tectonics:
-
What does negative vs. positive feedback mean?
- An example of Positive Feedback is initiating the rolling of a ball down a hill. The ball goes faster
and faster as it goes down the hill. In positive once something starts it continues changing on its
own.
- An example of Negative Feedback is pushing a ball up a hill
As soon as you stop pushing it will return to the bottom. Thus the system recovers. wow awful
example.
-
What does the term “orographic precipitation” mean? Describe the process
and what conditions do you need to cause it? At which locations (setting)
would you expect these conditions to occur?
Orographic precipitation, also known as relief precipitation, is precipitation generated by a
forced upward movement of air upon encountering a physiographic upland.
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Humid air forced to raise at a mountain range will cool and, thus, separate from its moisture. The
upwind side will experience heavy rainfall, whereas the lee side of mountains will experience
descending dry and warm winds.This creates a wind shadow. This form of precipitation occurs
near mountains, so most commonly along convergent boundaries.
What do we need to generate orographic precipitation?
-Orogen = mountain belt (e.g. Andes) or mountains (islands)
How can mountain belts affect climate/atmospheric circulations? (roughly)
Mountain ranges and elevated land masses have a major impact on global climate, for instance
-the elevated areas of East Africa or Andes substantially determines the strength of the Indian
monsoon. Formation of mountain belts can build an orographic barrier which changes air
currents (e.g. Andes)
- barrier width, slope steepness and updraft speed are major contributors for the optimal amount
and intensity of orographic precipitation. Basically, steeper and more narrow = more
orographic precip
Can climate influence deformation processes or even the isostasy processes
(how much the lithospheric plates float on the asthenospheric mantle)?
(rough ideas)
- formation of large continental plateaus can form heat sources and affect circulation
- climate can affect precipitation, which influences erosional processes such as
deformation and mountain building. This, in turn, affects Isostacy.
Thunderstorms/Tornadoes:
-
What is needed to create a thunderstorm over land? (conditions, air
masses)
·
Rising warm air masses or converging winds directly above the surface.
Thunderstorms form as unstable, warm (more buoyant) and moist air rapidly rising into colder
air and condenses. Because warm air is less dense than cold air, this added heat causes the
rising air to continue to rise in an updraft. This eventually causes a region of falling rain in an
outflow area of the storm when water droplets get large enough (through collision). If updrafts
push air high enough into the atmosphere, the water droplets freeze in the tops of
cumulonimbus clouds (which can reach the tropopause); these are the tall clouds that rise to
high altitudes and spread to form wide, flat, anvil-shaped tops. This is where lightning and
thunder commonly develop.
-
How would air move within storms and why?
Air that rises faster will also rotate faster. Storms are localized in zones of low pressure areas where
warm moist air rises rapidly, the faster rising air there rotates rapidly counter clockwise
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(N-Hemisphere) and clockwise (S-Hemisphere).
-
Name typical hazards which can be associated to thunderstorms? Describe
them.
-
Lightning: massive electrostatic discharge between the electrically charged regions within clouds
or between cloud and the surface of a planet
-
Strong winds: speed from 20-33 knots
-
Downbursts / microbursts (small areas of rapidly descending air, often affects aircrafts)
-
Hail-pellets of frozen rain that fall in showers from cumulonimbus clouds
-
Flashfloods-a sudden local flood, typically due to heavy rain.
-
Wildfires
-
Tornados
-
What is lightning (flash vs. strike) and how does it form?
Lightning is a massive electrostatic discharge between the electrically charged regions within clouds
or between cloud and the surface of a planet. The charge results from collisions (friction) between
rising and descending water droplets/ice crystals in the atmosphere (thunderstorm clouds). The
charged regions within the atmosphere temporarily equalize themselves through a lightning flash,
commonly called a strike if it hits an object on the ground.
-
What is thunder?
In a lightning strike, the negative charge in the cloud base jumps to join the positive charge on the
ground. Instant heating of the air in the surrounding channel to temperatures up to about 28,000°C
causes the air to expand at supersonic speed, which we recognize as thunder.
-
What is a tornado? What conditions are needed and how would a tornado
form?
Tornadoes are narrow condensation funnels of intense wind, often encircled by a cloud of debris and
dust. Tornadoes form by “wind shear,” winds approaching each other obliquely. They often have
a counter clockwise rotation and extend down from a cumulonimbus cloud while simultaneously
in contact with the cloud base and the ground.
(A tornado is a narrow condensation funnel of intense wind, often encircled by a cloud of debris and dust
forming in a convecting thunderstorm. Tornados descend from cumulonimbus clouds and often have a
counterclockwise rotation. Tornados form by “windshear“, (winds approaching each other obliquely;
surface winds approaching from the SE with winds from the W higher in the atmosphere).
Generally form when there is a shear in wind directions, such as surface winds approaching from the SE
with winds from the W higher in the atmosphere. Such shear can create a roll of horizontal currents in a
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supercell thunderstorm as warm, humid air rises over advancing cold air. Updraft makes roll (funnel) to be
uplifted on one side, thus connecting the thunderstorm cloud and the ground.
- Where do they form often in North America and why?
More than 90% of tornadoes in North America are developed in the United States and that is where
the term “US Tornado Alley” formed. They are often formed there because of the collision of
warm air moving north from The Gulf of Mexico and cold air moving south from Canada.
-
Is there a scale for tornado intensity or damage?
The Fujita scale (F-Scale), or Fujita–Pearson scale, is a scale for rating tornado intensity, based
primarily on the damage tornadoes inflict on human-built structures and vegetation. It ranges
from 1-6, however at stage 6 winds are not expected to ever reach the minimum amount to be
categorized as 6.
-
What are the main hazards associated with tornadoes?
Flying debris (cows)
dust devil- = strong, well-formed and relatively long-lived whirlwind, ranging from small (half a
meter wide, few meters tall) to large (more than 10 m wide, 1000m tall).
direct impact of tornado (destroying everything in it’s path basically)
Your house getting dropped on the sister of a wicked witch in the magical land of oz. lol
-
Can we predict/forecast tornado formation/path and which institutions
would do that?
There are storm prediction centers that try to predict tornadoes but it is very difficult to predict and
can only be done with little notice at most a day in advance. The US National Weather Service
and Canada Meteorological Service of Canada also attempt to predict tornadoes.
-
Name some measures you could take to minimize damage and injuries etc.
Develop a tornado plan and practice it with your family, have supplies ready and a predetermined
place to meet after the tornado is over. Try to go to a basement or room without windows. You
can cover yourself with a mattress to keep debris from falling and hitting you and if possible wear
a helmet. Be careful if you are outside during a tornado, seek shelter right away.
Hurricanes/Cyclones/Typhoons:
-
-
Name the two types of storms formed over the ocean and describe roughly the
differences.
Extratropical Storms (AKA Mid-Latitude Cyclones AKA Wave Cyclones)
o Occur in mid-latitudes outside
of the tropics
o Typically have weaker winds than tropical, but produce anything from mild showers to
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thunderstorms
o Cyclones usually have mild winds but can cause severe flooding
● COLD core
Tropical Storms
o Rapid rotating storm with a low pressure centre
o Strong winds
o Spiral arrangement of thunderstorms that produce heavy rain
● WARM core
-
-
Are there features similar to all storms we talked about in these lectures
(thunderstorms on land and offshore, violent and less violent)? If yes, which?
- Strong rains, winds, high waves, storm surges, tornadoes
-
How is the difference between a tropical storm and tropical cyclone/hurricane etc.
defined?
Tropical Storm – Wind speeds less than 119km/h, eye is not usually present
Tropical Cyclone – Wind speeds more than 119km/h, develops an eye
-
What is the difference between a cyclone, hurricane and typhoon?
Hurricanes, cyclones, and typhoons are all the same weather phenomenon; we just
use different names for these storms in different places
-
o In the Atlantic and Northeast Pacific, the term “hurricane” is used.
o In the Northwest Pacific is called a “typhoon”
o In the South Pacific and Indian Ocean is called “cyclone”
What do the Saffir-Simpson and Beaufort Scales measure and define?
intensity(storm surge) and wind speed
The SSHS classifies hurricanes into five categories distinguished by the intensities of their
sustained winds. To be classified as a hurricane, a tropical cyclone must have minimum???
sustained winds of at least 119 km/h (74-95 mph) (Category 1).
The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea
or on land. Its full name is the Beaufort wind force scale, although it is a measure of wind speed
and not of force in the scientific sense. Today, hurricane force winds are sometimes described as
Beaufort scale 12 through 16, very roughly related to the respective category speeds of the
Saffir–Simpson Hurricane Scale, by which actual hurricanes are measured, where Category 1 is
equivalent to Beaufort 12. However, the extended Beaufort numbers above 13 do not match the
Saffir–Simpson Scale.
Where and when do tropical cyclones etc. form in general and why do they move?
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· They form wherever there is a warmer climate - high humidity needed
· These storms occur over water in areas where the sea surface temperature is at least
26.5 degrees (>25 degrees) .
o They form between the Tropic of Cancer and the Tropic of Capricorn (hence the
name 'tropical' storm).
· They rarely occur within 5 degrees of latitude (555km) either side of the equator
because the Coriolis force is too weak here.
· Trade winds cause the moist air to spin inwards
o As the warmed, moist air rises and cools off, the water in the air forms towering
cumulonimbus thunderclouds (because there is a huge amount of
condensation)
o The whole system of clouds and wind spins and grows, fed by the ocean’s heat
and water evaporating from the surface.
-Tropical cyclone activity peaks in late summer, when the difference between
temperatures aloft and sea surface is the greatest. But each particular ocean basin has
its own seasonal patterns.
What conditions are needed and how do these kinds of storms form?
1) Water temperatures of at least 26.5 °C (79.7 °F) down to a depth of at least 50 m (160
ft);
o Waters of this temperature cause the overlying atmosphere to be unstable
enough to sustain convection and thunderstorms.
2) Rapid cooling with height
o Allows the release of the heat of condensation that powers a tropical cyclone.
3) High humidity, especially in the lower-to-mid troposphere
o When there is a great deal of moisture in the atmosphere, conditions are more
favorable for disturbances to develop.
4) Low amounts of wind shear
o High shear is disruptive to the storm's circulation.
5) Generally need to form more than 555 km (345 mi) or five degrees of latitude away
from the equator, allowing the Coriolis effect to deflect winds blowing towards the low
pressure center and creating a circulation.
6) A formative tropical cyclone needs a pre-existing system of disturbed weather.
· Tropical cyclones will not form spontaneously.
o Low-latitude and low-level westerly wind bursts associated with the
Madden-Julian oscillation can create favorable conditions for tropical
cyclogenesis by initiating tropical disturbances
-
Describe roughly the structure of these storms (velocity, pressure, size)
· Eye
o Normally circular in shape, and is typically 30–65 km (19–40 mi) in diameter
o Velocity = 33km/hr (lowest)
o Pressure = 960mb (lowest)
· Eye Wall
o Greatest wind speeds are found, air rises most rapidly, clouds reach to their
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highest altitude, and precipitation is the heaviest
o Velocity = 250km/hr (highest)
o Pressure = 1000mb
· From the eye wall to the edges of the storm, velocity decreases
-
What are the major hazards associated to cyclones/hurricanes/typhoons?
· Ocean
o Large waves
o Heavy rain
o High winds
o Interrupting international shipping, shipwrecks
· On Land (landfalling tropical cyclones)
o Strong winds
o In coastal regions: storm surges or increase of sea level
o Tornadoes
o Damage/destroy property, bridges, flying debris, erosion
-
Can we predict/forecast these storms and their tracks?
· Depends on determining position and strength of high- and low-pressure areas,
predicting how those areas will change during the life of the tropical system
· High-speed computers run simulations (models) to predict tropical cyclone tracks
based on future position and strength of high- and low pressure systems
· Forecasting models and vast data from satellites/other sensors increases accuracy
· Intensity hard to predict
-
How can we prepare for the storms and associated hazards?
· Move to higher ground (away from coast)
· Get supplies
· Prevent flying debris by fastening objects
· Keep informed
· Property inspections
· Insurance processes
Coastal environments and processes:
- Define the terms shoreline and coastline and what is the difference between them?
A shore or shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or
lake. In contrast to a coast, a shore can border any body of water, while the coast or coastline must
border an ocean; that is, a coast is a type of shore.
- How do astronomical processes influence shorelines?
The gravitational pull of the Sun and the Moon, and the rotation of Earth contribute to the
rise and fall of tides. The alignment of the Sun and the Moon with Earth determines the
time and amplitude of tides.
29
-
How do regular waves form in a water body and what are the main factors
influencing the wave height?
Wind pushes against water in oceans and forms waves through friction with the water. The
main factors influencing wave height are strength of the wind (Wind Energy), fetch
(length of water that wind moves over) and amount of time the wind blows.
- Describe the wave motion and wave parameters.
Wave Properties
· The energy source for both coastal erosion and sediment transport are the ocean
waves
o Generated by the frictional effect of the winds incident on the ocean surface
· Kinetic Energy: The motion of the water within the wave.
· Potential Energy: Due to the position of water above the wave trough.
· Wave energy increases with wind speed and fetch
Wave Motion
· Ocean Depth > ½ Wavelength
o Waves not affected by ocean floor
· Ocean Depth < ½ Wavelength
o Wave height increases and wavelength decreases
· When the wave becomes more peaked “Breakers” form
· Breaking of waves: Conversion of potential to kinetic energy
o Work done on the shoreline
Which is more significant for shorelines regarding erosion, material transport and
deposition, tides or waves?
- Waves. The energy for both coastal erosion and sediment transport comes from ocean
waves.
- What does happen when waves approach the shore and why does it happen?
There is a decrease in wavelength as waves approach a shoreline. This causes the wave height to
increase and the waves may “break.” The waves drag on the bottom and their crest leans forward
causing the top to collapse or “break.”
-
Explain both wave refraction processes: longshore drift and the process leading
to shoreline straightening.
Wave Refraction: Longshore Drift
Waves approach the shore at an angle. Part of the wave hits the bottom (drag on bottom and
slows down, breaks) earlier than others (still in deeper water, wave still moves faster, does not
break yet), what results in a curve (refraction) of wave crest (surf) towards the shore.
ALSO: Grains are washed up the shore obliquely but are transported back orthogonal (following
gravity) to the shore line as the water retreats.
Wave Refraction: Shore Straightening
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Waves approaching steep coasts encounter rocky points called headlands separated by
shallower sandy bays/coves that reach into deeper water. Erosion of headlands, deposition of
sand in coves leads to straightening of coastlines.
- Explain roughly what a rip current is and why it can be dangerous.
A rip current is a very strong channel of water flowing seaward from near the shore. These rip
currents are very dangerous as they can pull a person out into deep water and hold them under
water as well. If you are caught in a rip current then you should swim parallel to the shore to get
out of the current. Permanent rip currents can develop at groins, jetties, or rock outcrops, where
water flowing against those structures piles up and is forced to flow offshore along the structure.
·
Where does the sediment (sand etc.) of a beach come from and why is it so
important to have beaches?
Accumulation of sand comes from coastal erosion and rivers
o E.g. Longshore Transport
● Provide recreational opportunities for millions of people.
● Provide some protection to residents living near the ocean by acting as a buffer
against the high winds and waves of powerful storms or rough seas
● Beaches are sensitive environments that supports a variety of plants and animals.
-
Name the typical erosional vs. depositional landforms (know roughly how they
form).
Erosional processes and landforms:
- Erosion of gently sloping shorelines and barrier islands
- Erosion of steep cliffs: Wave-cut Notches, Caves, Stacks, Arches
Deposition processes and landforms:
Processes: tides, waves
- Beaches: formed from waves and tide transporting and depositing sediment along the shore
- Barrier Spit, Baymouth Bar: Material deposited along a ridge, extending outward from a coast.
When it grew to completely block an embayment, it’s called a bay barrier or baymouth bar.
Barrier Islands: Form where the slope of a continental shelf is shallower than the equilibrium
profile of the beach.
- Lagoon: body of water behind a bay barrier/baymouth bar
- Tombolo: occurs when sediment deposits connect the shoreline with an offshore stack or island
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- What factors affect erosion of shorelines and why (roughly)?
Energy of wave action, resistance to erosion and the particle size
Erosion rate and particle size depend on rock type of cliff (rock strength), wave height, sea
level, and precipitation (all affected by intermittent events e.g. El Nino or storms =
frequency and intensity)
-
What does “undercutting/wave-cut” mean?
Undercutting: A rock recess at the foot of a sea cliff where the energy of waves is
concentrated e.g., sea cliffs
Basically the erosion of the rock at water level, leaving the rock above, untouched. Can
someone tell me how to join pq?
- How are beach slope and particle size related to each other?
Shallower water, smaller waves and coarser grains promote steeper slopes. Fine sands can be moved
on a gentle slope, coarse sand or pebbles only on a much steeper slope.
- What factors affect the location of particle deposition?
- Size of particles, wave/current speed and direction
-
Why are barrier islands, reefs, sand bars, dunes, vegetation etc. along the
shoreline so important features?
These features help decrease the effects of erosion on our beaches. Major storms wash sand both
landward into lagoons and seaward from the barrier island/beach. Sand moves back up onto the
higher beach in milder weather and wind blows some dry sand into dunes again. Reefs also
deliver an abundant amount of services to fisheries and tourism.
-
Think of some processes which would be affected by sea level rise or fall and
why? (roughly)
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Emergent coastline
·
Occur due to fall in sea level
·
Because of either a global sea level change or a local uplift
·
Typically coastal landforms are above high tide marks
·
e.g. cliffs, raised beaches
Submergent coastline
·
Occur due to sea level rise
·
Due to global sea level change
·
Local subsidence or isostatic rebound
Also the coral reefs are affected. If the sea level is too low then it causes it to dry out and
a newer reef will form in the lower level while if the sea level rises too high then the reef
may die out since the plants cannot get enough sunlight.
-
Which short and long term effects can be cause by coastal processes and how
can these be hazards?
Short term: storms (extratropical and tropical) inl. storm surge, waves, flooding, beach and cliff
erosion, debris, overwash and inland flooding.
Long term: erosion of cliffs and beaches, subsequent cliff collapse, due to normal wave action,
undercutting and overwash. There are extreme winds, the sea level rises, and tsunamis.
-
What countermeasures are there to hinder for the population problematic coastal
processes, and how can these in turn be negative?
Beach erosion:
Construction of seawalls, and riprap (hardening the beaches) began as coastal areas gained in
population, including tourism. These structures were meant to decrease erosion but they actually
accelerate erosion.
Boulders are deposited below soft cliffs in an attempt to arrest erosion. Big boulders or ripraps only
reflect off waves -> erosion/washing out of sand around them, steepening remaining beach.
Groins and riprap walls(jetties) are built out into the surf to trap sand and to prevent it from migrating
down the beach. Problem: This displaces site of erosion further down the beach.
Breakwaters cause a deposition of sediment in the protected area behind the barriers. Problem: This
displaces the site of erosion further down the beach.
Beach replenishment:
Dredging of sand from a river outlet and replenishment of the downstream section of the beach. But
this is very expensive, tedious and likely ineffective. It needs to be done in a sensible manner. Not
every type of sand is suitable for this purpose.
- What does beach hardening mean?
Construction of seawalls, and riprap and other structures hardens the beach by reflecting waves off
the barrier and transporting the sand offshore. This leaves the beach with a rocky, rough
landscape.
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- What are necessary measures for risk assessment and damage control?
Establish context
· Coastal location, existing hazards exposure, information availability, decision
timeframe etc.
Assess Vulnerability
· Probability, magnitude, frequency, consequences
Evaluate Risks
· Precautionary approach focussed on impacts on people, property, communities,
infrastructure and environment (risk maps)
Response Strategy
· Avoid, retreat, accommodate, protect, apply precautionary approach
-
What conclusion did some (hopefully soon more and more other) authorities and
communities draw from the last decades efforts to prevent and control damage,
and how would a new approach include?
From slide: “Enhance ability of all communities to apply best available hazards information, tools
and technologies to maximize community resilience to coastal hazards and flooding.”
Any changes implemented to control and prevent damage have lead to increased erosion
elsewhere. Erosion is a natural process that cannot be easily controlled. The new approach
should include zoning for appropriate coastal land use thus moving populations further back
away from shorelines. The new approach is to try and control the human activities and not the
erosional environment.
Tsunamis
1. What does the term tsunami mean?
Tsunami, is the Japanese word for Harbor wave. Tsunami’s are named Harbor wave
because the waves rise highest, where they are focused into bays or harbors
2. How do tsunamis differ from wind-driven waves?
- increased wave period, velocity, wavelength, momentum
- tide reaches all the way to the sea bottom
- Wind driven waves travel in a circular motion and do not flood the coast, whereas
tsunami travel much like a wall of water that floods the coast
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3. Name and describe the main events causing tsunami, which is the most
frequent cause of tsunamis?
Earthquake generate Tsunami’s – most tsunamis are generated during shallow-focus underwater
earthquakes associated with the sudden rise of the seafloor, which displaces a large amount of
water. Earthquake-generated tsunami occur most commonly by displacement of the ocean
bottom on a reverse- or thrust-fault movement on a subduction-zone fault. During subduction
the ocean floor slides under the continent, the boundary between the two plate’s sticks. Where
the plates stick, the continent edge is pulled downward and towards the continent as the
subducting plates moves under it. This causes the overlying plate to flex upward (Think of a piece
of paper, if you curve the sides, the middle bulges up). The stuck area then ruptures and releases
energy in an earthquake, the edge of the continent will snap oceanward displacing a huge
amount of water. The tsunami wave will then move towards the continent and away from it.
Tsuanmi’s generated by Volcanic eruptions – Water is driven upward or outward by fast moving
flows of hot volcanic ash. The displacement of water is cause by underwater eruptions. However,
we do not know much about tsunami’s generated by volcanic eruptions except that it can be
very catastrophic
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Tsunami’s from fast moving landslides or rockfalls – when major fast-moving rockfalls or
landslides enter the ocean, they can displace immense amounts of water. Tsunami’s depend
primarily on the height of fall not so much the volume of the mass.
Tsunami’s from volcanic flank collapse – The flanks of many major oceanic volcanoes collapses on
occasion and slides into the ocean, displacing thousands of cubic kilometers of water
4. What influences the height of tsunamis caused by earthquakes? Does the
direction of motion affect the intensity of tsunami and if yes, how?
- Shoaling influences height of tsunami caused by earthquakes
- Shoaling= hitting the bottom of the ocean
- it compresses the wave and increases the amplitude
- water behind it begins to build up
How deep the water is, the depth of the center of the earthquake & how far the vertical
movement of the snapping of the leading edge (not horizontal) are the main factors
affecting the height of tsunamis. so these factors affect the height of the tsunamis and
not shoaling?
5. Is the motion of a tsunami wave orbital (for a particle in the water)? What effect
does this have at the beach?
No, motion of a tsunami wave is NOT orbital. Mechanisms that drive tsunami waves are different
from those that drive typical waves. Tsunami waves, have extremely long wavelengths so they
drag on the bottom everywhere in the ocean. Because a tsunami feels bottom far from shore, it
gains amplitude to become a wall of water, as it rides over the continental shelf and approaches
land. When the wave hits the beach, it causes massive movements of everything (debris, people,
structures) on the beach, dragging everything out into the water. This would cause sediment on
the beach to be moved and deposited irregularly and at a much faster rate.
No, instead of orbital (circular motions on top of each other) like wind waves, tsunamis have
circular motions side by side each other (like the wheels of a train hence the name “wave train”).
This causes the first wave to draw water back towards the next wave to increase momentum and
as such they can carry debris and deposit it much further inland than regular waves.
6. How far can tsunamis travel? What is the velocity/height of a tsunami in the
open water compared to when it hits the coast? Which waves is more likely the
most destructive?
In open waters the waves from a tsunami could travel halfway around the world.
- velocity= 700 to 870 km/h
- most tsunami height= few meters (in open ocean)
- dangerous tsunamis have several meters (near coast)
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- height depends on depth
- high depth= low height
The third and consecutive waves are often the most dangerous and destructive.
7. Are coves, harbors or bays more secure than long straight stretches of beach if
a tsunami hits the coast? Why?
The effects of tsunami are amplified by coastal bays, river mouths, and tides so they are not
safer. the mouths of rivers and coastal bays funnel the waves and dramatically raise their height.
8. Why did the tsunami in 2004 (Sumatra) end up being such a catastrophe
compared to the tsunami in 2011 (Japan)?
Over time (2004-2011), they probably have developed better warning systems and evacuation
procedures.
She said in class that the Japanese have one of the best tsunami detection systems and also if u
look at the slide Tsunami-History (12) it says that the Japanese wave was only 10m high
compared to Sumatara which was 33m high.
9. Can we find evidence of historical tsunami events? Which?
- Santorini Tsunami led to downfall of Minoan Culture (1600 BC)
- Atlantis story ←-LOL is this legit? Of course it is.
- Can see fossil evidence; wherever there is a pattern of topsoil, sand, peat and grass.
This is because when the tsunami strikes, it takes out trees (the stumps become fossils)
and deposits sand, mud and soil at different places/rates.
10. What are the main steps for a well working hazard mitigation process for
tsunamis?
- Engineering of structures to protect against the waves (tsunami walls)
- Land-use planning; having more low-lying lands near water
- Building guides for houses/other structures such as tsunami towers where people can
take refuge. Building more accessible roads for easier evacuation.
Rivers & Floods
1. What are floods and what different types of floods are there?
A flood is an overflow of water that submerges an area of land.
Different Types of Floods:
Flash (areal, rain fall) Flood
-In flat or low-lying areas when the ground is saturated and water either cannot run off or stop
accumulating
-If water falls on impermeable surfaces (dry soil, concrete, paving, frozen ground)
-Localized heavy rain from a series of storms can cause areal flash floods when rain exceeds
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drainage capacity of area
Estuarine (Coastal) Flooding
Occurs in estuaries and commonly caused by a combination of tidal surge, winds, storms, and
is enhanced by high upstream river flow
Urban Flooding
-Flooding of land/property in a built environment, caused by rainfall overwhelming the capacity
of drainage systems (storm sewers)
-Can be triggered by flash flood, snowmelt, but must be a repetitive and systemic impact on
communities
Riverine Flood
-When flow rate exceeds the capacity of the river channel (bends, meanders)
-Cause damage to homes and businesses built on flood plain
2. What causes floods along rivers? Name the main sources of floodwater
-When flow rate exceeds the capacity of the river channel
- The inability of the ground to absorb the surface runoff (low absorption and infiltration
rate)
- Large amounts of sediment deposit chokes channels, causing them to flood
- Non-vegetated areas cannot soak up water so things like forest fires and deforestation
causes floods
-Sources of Water: Groundwater Seepage and Surface Water
Flood are usually caused by heavy rain, heavy thunderstorms – but sometimes by ice or snow melting (thawing).
Storms for coastal areas, rainfall/snowmelt in rivers
3. Name the parameter used to characterize floods
Discharge --> Q = V x A (Velocity of water flow times cross-sectional area
4. What variables affect the intensity of floods?
Slope steepness, Basin area and shape
Spacing of drainage channels, Vegetation cover
Soil permeability, Land usage
5. What is a river?
a large natural stream of water flowing in a channel to the sea, a lake, or another such stream.
6. Name and describe (briefly) the main parts of a river (from source to end)
1) Source
o Where water originates from precipitation or meltwater
2) Tributaries
o Smaller streams of water that come from different sources of water
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3) Confluence
o Junction where tributaries converge
4) Main River
5) Meandering Streams
o From the main river, these tend to have a curvature pattern where deposition and
erosion of sediment occurs
6) Mouth (estuary)
o River water feeds into a larger body of water such as an ocean
7. What do the terms runoff, stream gradient (stream profile), stream cross-section
and base level mean?
Runoff
● Water does not get absorbed into land since it flows over saturated areas from
different sources (meltwater or rain)
● Can lead to flooding in some areas and erosion
Stream Gradient (Stream Profile)
● Is a measurement of drop in elevation of a stream per unit of distance (E.g.
Meters per Kilometer)
Stream Cross-Section
● Stream Width x Average Water Depth
● Visual representation (Plane cutting through a stream at right angles) to measure
rate of stream flow
Base Level
● “Mouth of the River”
● The lowest elevation of where a river can flow and erode
8. How is stream flow characterized? (Formula and explanation)
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- Discharge or Flow: total volume of water flowing per unit of time (average water
velocity multiplied by cross sectional area of stream, harder to do)
- Stream flow/ Discharge (Q)= Velocity (v) * Cross Sectional Area (A)
- Divide the river into a rectangular grid and measure the cross sectional area (Width x
height of each rectangle), multiply it by the velocity of each grid section. The sum of all of
these cross sectional area x velocity is the stream flow.
o Stream flow = sum of(Vn*An)
9. What factors can cause high stream flow? How/why?
Magnitude of precipitation
Rate of runoff
Type of bedrock
10. Which three natural processes are influenced by the intensity of stream flow?
- Erosion, sediment transport and deposition
11. How does a river adjust itself (shape) and why?
- The cross section adjusts to accommodate flow, sediment volume and grain size (in
the channel).
- Their gradient changes in response to water velocity, sediment size and sediment load
to allow the river to transport the supplied sediment properly over time
- Erosion and sediment deposition can change the shape of a stream too.
12. What is a dynamic equilibrium?
- Balancing process associated with a set of interrelated stream physical adjustments
that naturally maintain stream channels in their most efficient and least erosive form.
Dynamic means that the energy of a stream is always changing, so an equilibrium
constantly needs to be reestablished. Any stream able to maintain eq’m is called a
graded stream
13. How do erosion, transport and deposition change with flow velocity and
sediment grain size?
- Volume and velocity of water flow limit the size and amount of sediment that a stream
can carry
- Fine particles require high velocities for erosion
- The speed required to erode particles is greater than the speed needed to transport
particles
-the larger the grain size, the greater the velocity required to erode and move and
deposit them
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Grain size decrease downstream as slope decreases in a stream channel
from turbulent, high energy rivers in mountains (steeper gradient) to more gentle
sloping and less turbulent river channels in the low lands (lower gradient).
14. How can sediment be transported?
- Via streams, rivers, levees. Streams and rivers carry sediment downstream with the
water.
15. Describe the relationship between sediment grain size and slope.rr
grain size INCREASES with increased slope (top left of this figure), grain size increases
as you move up but there are exceptions such as clay. clay sticks well together to even
though it is small due to charges acting btw the small particles.
16. Describe the various types of rivers/streams and the main differences in
formation, shape, location, climate, etc
- Bedrock Streams: are fast moving, high energy streams that occur in steep,
mountainous areas where the stream bed is solid rock).
- Develops when stream erodes down to resistant bedrock
- Abrupt change in gradient (knickpoint) from bedrock section to braided or
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meander section of stream
- Vortices or whirlpools can form and drill potholes in bedrock
- Meandering: Most common in wet climate with finer-grained sediment
- Any irregularity that diverts water toward one bank helps erode that bank and
causes the meandering
- Thalweg: deep and highest-velocity part of stream
- Streams preferentially erode outside bank of meander bends
- Sediment deposited as point bar along inside of bend
- Meander can come closer and closer together until floodwater breaks through
neck between them, creating cutoff straight channel and oxbow lake in
abandoned meander
- Erosion and deposition of meanders over long term moves river back and
forth to create broad valley bottom = flood plain
-Braided: Common in dry climates with abundant coarse sediment.
- Do not meander, instead form broad, multi-channel paths
- Overloaded with sediment that is deposited in islands between small channels
- Promoted by dry climate with little vegetation protecting slopes from erosion
- Characterized by eroding banks, steep gradient, abundant stream bedload
- Form alluvial fan where braided stream lowers gradient
Particularly dangerous flood areas.
17. Where do alluvial fans form in general and how are they connected to
streams/rivers?
- An alluvial fan is a fan- or cone-shaped deposit of sediment crossed and built up
by streams. These flows come from a single point source at the apex of the fan, and over
time move to occupy many positions on the fan surface. Fans are typically found where a
canyon draining from mountainous terrain emerges out onto a flatter plain, and
especially along fault-bounded mountain fronts
18. What are the differences between gaining and losing streams?
Depends on how wet or dry a climate is.
Gaining Streams: In wet climates, groundwater flows into streams, to ensure year round
flow
Losing Streams: In dry climates, water from streams enters the ground as groundwater.
The stream can become completely dry from this process, until there is another
rainstorm
Gaining streams are fed by groundwater
Losing streams lose water into the ground
19. Describe roughly how a channel’s cross sectional shape would change during
the course of a flood
- During the course of a flood, a channel’s cross sectional shape will get larger. ie, the
channel will get deeper during a flood. This is because during a flood, water flow
increases in speed and volume, increasing erosion of the bottom of the channel, making
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it deeper.
20. How do levees form and why are they important?
- Levees form during/after floods. The flood spills over the bank of a stream/river
depositing sediment along the edge/bank of the channel. Over many floods, the
sediment piles up high, creating a “wall” around channels.
- They are important because they help to regulate water levels/prevent further floods
21. How would the discharge change when a river (first in its deep channel) flows
onto the floodplain?
- The discharge would decrease as the river flowed onto the floodplain. This is because
as it spills over, the volume of water in the river decreases, therefore decreasing the
cross-sectional area.How can this be right if in quesiton 19 we said cross sectional area
increases. If discharge is equal to cross sectional area multipled by velocity, shouldnt
discharge increase if we said in question 19 that cross sectional area increased?Cross
sectional area increases as flow increases, not the other way around, it does not work
both ways. floodplain is not part of the river in this context, so if water flows out of river
the discharge would decrease. but it says flows onto floodplain, ya its flowing out of river
into floodplain and the discharge is regarded to how much water is in the river but
wouldnt water always flow out of the river during a flood? so wouldn’t it always
decrease? initially during flood the water levels rise in a river eg. if it rains too much its
going to rise river levels with is going to lead to flooding of surrounding areas. ahh, so
intially when it’s filling up the X-sectional area increases but once it flows out into the
flood plain it decreases along with discharge? yes thanks! good luck tmw np good luck to
you too :)
22. What is a hydrograph? How do they help to show the effects of urbanization?
Hydrograph: A graph displaying stream water volume (Stream Discharge) Vs. time
With urbanization, overall water levels after flooding are relatively the same in
comparison to a rural area. However, there will be a much higher amount of water
volume in urban areas initially for a flooding event in comparison to a rural area. Urban
areas do not allow for effective removal of an increase in water volume since water
cannot easily be removed when there are large areas of pavement that are not
permeable to water.
23. What does the term stream order mean and what effect does it have on floods
(downstream)?
Tributaries (stream/river flowing into another river - does not have direct connection to sea or
ocean) are sometimes listed starting with those nearest to the source of the river (1) and ending
with those nearest to the mouth of the river (E.g. 3, 4, 5...n). The Stream Order examines the
arrangement of tributaries in a hierarchy of first, second, third, and higher orders, with the first
order tributary being typically the least in size. For example, a second order tributary would be
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the result of two or more first order tributaries combining to form the second order tributary. can
someone explain the text in red please What they mean is that if you are assigned 1, it means
you are a small river that doesn’t connect with another small river, if you are 2 it means that you
are the result of two small rivers coming together, 3 means you are 3 rivers coming together. The
biggest number has the most connections and closest to mouth which is where the river emptties
into the ocean or large body of water.thank you. Remember though that stream order is NOT a
sum of rivers. I.e. 2+2 does not equal 4. 2+2=3 (see Figure on slide 19)
The number of tributaries of a stream has a significant effect on the rate of floodwater rise during
and following a storm.
Additional Notes:
-Stream order from lowest stream order of the small tributaries (highest elevation points, kind of the start
points of the water flow) to the highest stream order of the main river close flowing to the base level (or
mouth).
-Low order streams: rapid response to storm, steep hydrographs, water travels short distances and carries
coarser and larger volumes of sediment. Flood warning time is short.
24. What are the main hazards and effects of riverine floods?
Hazards
● Erosion
● Scour (Depth of sediment that is eroded in a channel, during a flood)
● Mudflows
Primary Effects
● Infrastructure is damaged (Bridges, Sewer Systems, Power)
● Interaction with hazardous materials
● Water borne disease transmission
● Contaminated groundwater
● Death
● Negative effects on agriculture (Loss of crops)
● Difficulties in mobilizing treatment and aid
Secondary Effects
● Economic hardship (Decrease in tourism, rebuilding costs, food shortage...etc)
● Psychological trauma to those affected by the flooding
25. Name the main steps for well-organized flood mitigation
- Forecasting, damage control and reaction time.
- Control (basins, levees, reservoirs, etc to protect against effects of floods) Defenses such as
detention basins, levees, bunds, reservoirs, and weirs are used to prevent waterways from
overflowing their banks. When these defences fail, emergency measures such as sandbags or
portable inflatable tubes are often used to try and stem flooding.
-sea walls, beach nourishment, and barrier islands
-erosion control measures can be taken to try and slow down or reverse the natural forces that
cause many waterways to meander over long periods of time. Flood controls, such as dams, can
be built and maintained over time to try and reduce the occurrence and severity of floods as well.
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26. Any limitations of commonly used flood control measures?
- There are engineering limitations. Although dams, floodwalls and levees work, they
don’t contain all flood and most structures fail with age.
- Straightening of streams causes stream speeds to increase, increasing erosion. It can
also increase flooding in downstream areas
27. Name some structures (engineering) formerly built for control floods, which
had negative effects
- A levee may fail by overtopping, seeping through, or piping. Even where a levee is not
overtopped, water may percolate through porous areas to cause seeps, landslides in its
flanks, and ultimate collapse. Seepage from the river channel beneath the levee can rise
behind the levee to form sand boils and, ultimately, flooding on the flood plain.
- Flood walls can also cause increase flooding down the line by straightening a river and
increasing the water’s velocity! (Ft. Wayne, Indiana)
28. Have a rough idea what the new philosophy behind flood control is nowadays
- Discharging flood flow is the first choice, as well as reservoir storage
- Give rivers the room needed to enlarge channel capacity (remove man made structures
impeding natural river processes)
- Instead, improve flood management systems, have more accurate forecasts and
relocate populations living inside high-risk flood areas
Mass Flows
What does the term slope failure or mass wasting mean?
Slope Failure, also known as Mass wasting, slope movement, or mass movement
· The process by which soil, sand, and rock move downslope typically as a mass, under
the force of gravity, but frequently affected by water and water content as in
submarine environments and mudslides
Which two major forces act on slopes (stability vs. failure)? And which other
parameter are involved? Which do promote stability, which failure, and why?
(Know what terms mean!)
Driving forces and Resisting forces
· Driving forces promote downslope movement of material = Gravity.
· Resisting forces deter movement = material’s shear strength.
o Shear strength is a function of Cohesion (ability of particles to attract and hold
each other together) and Internal Friction (friction between grains within a
material).
Stability Parameters
· Gravity (F)
· Load (weight, L)
· Slope angle (α)
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· Frictional resistance (f)
· Cohesion (C)
· Pore pressure (p)
Factors Causing Slope Failure
o Increase in load
o Increase in slope angle
o Decrease in mechanical strength of material (e.g. chemical weathering,
increase of pore pressure)
· Name the internal properties of sediments which can influence slope stability.
· Moisture and Capillary Cohesion
o Static charge between minute clay particles
o Areas (pores) where thin water film can coat clay particles
o Surface tension holds the grains together
· Mineral/Grain Arrangement
o The molecular structure of some clay minerals enables swelling by
incorporating water in their crystal structure
o Water can be adsorbed or absorbed by minerals in the soil.
o Adsorption causes the electronically polar water molecule to attach itself to
the surface of the minerals.
o Absorption causes the minerals to take the water molecules into their
structure.
o By adding water in this fashion, the weight of the soil or rock is increased
· Internal Surfaces
o Zones of weakness lead to less cohesive/non-cemented sediments on top
leading to contacts/fractures etc. activated as slip planes (water or clay
minerals on the surface can decreases cohesion/friction)
o If dipping parallel to the slope these layers/surfaces (even more if dipping
downslope) are even more prone
·
When does moisture (water content) in sediments have positive effects and when
negative? How does the angle of repose fit in this system? Use terms please!
Positive Effects
A little bit of water increases cohesion by increasing surface tension
between clay particles
Negative Effects
· Adding too much water moisture between clay particles reduces cohesion,
increasing the load on a slope, and causing it to flow
· The water pressure at the base of each column is determined by the height of
the water above it and therefore its load.
o More water in the slope raises the level of water in the soil, called the water
table, and increases the pressure in the pore spaces at depth
o The weight of water above a point in the ground provides water pressure that
pushes mineral grains apart.
● That further weakens the soil and makes it more likely to slide.
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·
Angle of Repose: Steepest angle at which loose material is still stable
● A steeper angle is possible with less moisture
There are 3 different ways to reach liquefaction. Name these and have a rough
understanding how they work.
- Loss of Bearing Capacity: decreased capacity of soil to support the loads applied to the
ground.
- Ground Oscillation: the surface layer, riding on a buried liquefied layer, is thrown back and
forth by the ground shaking during an earthquake and can be severely deformed.
- & Subsidence: the gradual caving in or sinking of an area of land.
- Flow Failure: earth moves down steep slope with large displacement and much internal
disruption of material.
How can internal surfaces affect slope stability? What does the term “daylighted
bed” mean?
Daylighted Bed
·Internal surfaces that dip at gentler angles than the slope of a hill and can
intersect the lower slope
· Are often exposed at their lower ends by a road cut or stream and make ideal
zones for slippage.
o There is no resisting load holding them back, only the friction between the
layers, along with cohesion, can keep the mass from sliding.
o The rock above the slip surface does not have to push any rock out of the
way to start sliding.
What is the difference between flow, slide, fall and topple?
Flow (Creep, Rock Flow, Rock Avalanche)
· Downslope movement of unconsolidated material.
· Particles move around and mix with the mass.
o Creep: Velocity = 0.33mm/year-2.6cm/month (Slowest)
o Rock Flow: Velocity = Up to 10cm/s (Mid)
o Rock Avalanche: Velocity = 100cm/s (Fastest)
Slide (Rotational and Translational)
· Downslope movement of a coherent block of earth material
· Velocity = 6cm/minute
Fall
· Free fall of earth material, as from a cliff, the free face of a slope
· Velocity = 100cm/s
Topple
forward rotation out of the slope of mass of soil or rock about. sometimes
driven by gravity exerted by material upslope of the displaced mass and by water
·
Name the typical external triggers for mass flows.
· Earthquakes (liquefaction)
· Volcanic Eruptions (violent eruption, deposits increase load)
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· Adding Water (decrease friction, increase water pressure)
o E.g.: Prolonged rainfall, agriculture, water reservoirs
· Increasing Load (adding material on top of slope)
· Oversteepening
o E.g.: Road cut, undercutting by water removing material at toe
· Removing Vegetation (enhanced erosion)
· Human Activities (Vibration of machinery, blasting, deforestation, earthwork)
·
What types of mass flows are there (sorted by velocity)? Name and describe
subgroups if there are any.
o Creep: Velocity = 0.33mm/year-2.6cm/month (Slowest)
o Rock Flow: Velocity = Up to 10cm/s (Mid)
o Rock Avalanche: Velocity = 100cm/s (Fastest)
Subgroups???
Have a rough idea about risk management regarding mass wasting processes
(defense etc.).
- Can do mapping of landforms, lithologies, slopes, loose material, location of previous
slides, groundwater levels
- Mitigation strategies are restricted development in at risk areas, Water removal, Rock
Bolts, Concrete slope stabilizers, Drainage systems
For which of these hazards can we see evidence in Hamilton?
- Escarpment; see retaining walls. Also on James mountain access, there was a landslide,
knocking over the retaining wall, causing the permanent closure of one lane.
Droughts:
Define the term drought and name the typical causes.
A drought is a period of prolonged dry climate events in a region. There is a drop
in water level, not caused by a dramatic abrupt event. The typical causes
include: Lower than usual rainfall, rising temperatures, and human intervention
(Deforestation, river damming, increased water use, etc.).
Where can it occur and why does it have more fatal effects in the developing
countries than in developed countries?
They can occur anywhere around the world where there is less than average
rainfall.
Areas that are excessively hot and dry (around the equator) usually are the
most affected.
Developing countries are usually located in these areas so they are the most
affected since they rely on agriculture heavily in these parts but are subject to
very hot temperatures.
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Name the three stages a drought can have. Can these also occur each
individually? If yes, what might be the cause?
There is a progression over time for drought types that depend on amount of
precipitation…but other effects are possible
Meteorological-->Agricultural-->Hydrological
Meteorological Drought
o Prolonged period with less than average rain
o Usually precedes other drought types
Agricultural Drought
o Drought resulting in lower crop production
o Links various characteristics of meteorological (or hydrological) drought to
agricultural impacts, focusing on precipitation shortages, soil water deficits,
reduced ground water or reservoir levels needed for irrigation
Hydrological Drought
o Tends to show up more slowly because it involves stored water that is used but
not replenished.
o Occurs following periods of extended precipitation shortfalls that impact water
supply (i.e., streamflow, reservoir and lake levels, ground water), potentially
resulting in significant societal impact
● Like an agricultural drought, this can be triggered by more than just a loss of
rainfall
· Name some effects of droughts (on humans, ecosystem, and economy).
- Famine: Drought can lead to crop failures and livestock deaths that can lead to
undernourishment and famine (hunger crises due to food shortages).
- Biodiversity Loss
- Disease of crops and insect infestations
- Conflict (social and political upheaval, war, may even cause total collapse of
civilisation
- Refugees
- Desertification
- Economic Loss (financial distress to farm families and business)
- Dependency
· Review risk management!
Improved monitoring, water/crop management, increase of water supplies, public
awareness & education, watershed and local planning, reduction of water demand, water
conservation.
Wildfires:
· Define what wildfires are.
Wildfires· is an uncontrolled fire in an area of combustible vegetation that occurs in the
countryside or a wilderness area.
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·
-
Do wildfires have only negative effects? Please explain why yes or no.
No
o There are positive effects of wildfires too.
Positive effects include permitting growth of new species and age
groups of trees, thinning forests and reducing understory fuel
·
Name the components without which a wildfire would not burn. What additional
important factors are there for wildfires and how can they affect fires?
Components needed:
- Heat
- Oxygen
- Fuel: Shrubs, trees, grass, oils, saps, houses etc.
The larger the surface area of combustibles, the easier they will burn.
The type of fuel available, its distribution, and its moisture content determine how quickly a
fire ignites and spreads, as well as how much energy it releases. Also weather and
topography
·
What does the term “fuel” mean? Name the three different plant tissue groups
mentioned during the lecture.
Fuel is a material that is burned to produce heat or power
Important factors of Wood/Plant tissue (fuel):
Cellulose / hemicellulose (burn at low temp.)
Lignin (glowing combustion, smolder(burn slowly with smoke but no flame) for long
time)
Extractables (resins, fats, oils, terpenes: low boiling points, flame suddenly; fats, resins:
produce gases and tars)
· What can cause a wildfire?
Lightning, debris burns, arson, unintentional.
·
Name the three (or four) stages of wildfire combustion. What does the term
combustion stand for?
1. Preheating = Preignition = Pyrolysis:
Thermal degradation of the fuel = “heat divided”
( ~250 – 355 C )
à char (low temperatures = glowing)
à tar (high temperatures = volatile gases = flaming)
à mineral ash (inorganics)
2. Ignition (lightning, spontaneous, induced)
Transition between pre-ignition and combustion
- Low temps = charring à glowing combustion
- High temps = gases à flaming combustion
Spontaneous ignition: Pile heating (heat liberated faster than lost to surroundings), chip
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piles: fresh chips + foliage, moisture > 20%, pile > 1m in height; Microbial activity =
respiration à CO2 + H2O + HEAT
Requirements for ignition: Oxygen + formation of char
- surface oxidation of char = smoldering
- smoldering à heat à continuous pyrolysis (flaming)
3. Combustion:
a. Smoldering or glowing:
• Surface fires: Lower temps, but longer duration
• Ground fires in organic soil horizons: smolder for mo/yrs (potential for
re-ignition)
• High smoke production (particulates, CO)
b. Flaming:
• Volatile gases mix with air = flames
• High temperatures necessary (425-480 C)
• In general, fewer emissions than smoldering fires
4. Extinction / termination of combustion:
Two important factors can cause smoldering to cease:
- Inorganic materials (ash) – absorb heat but do not oxidize – reduces the total amount of
heat
- Not enough heat produced to cause vaporization in moist fuels (no more “available fuel”)
· Do wildfires absorb or emit energy? Explain.
absorbs heat in the pre-ignition phase. releases heat in the ignition and combustion phase
· Name the four different types of wildfires and describe them.
1. Ground fires: subterranean roots/duff/buried organic matter, burn by smoldering, slow
over days/month, e.g. Peat fires
2. Crawling or surface fires: low-lying vegetation (e.g. leaf/timber litter or debris, grass,
shrubbery)
3. Ladder fires: material between low-level and canopy level (e.g. small trees, vines)
4. Crown or canopy or aerial fires: burn suspended material at canopy level (e.g. Tall trees,
vines, mosses), ignition process = “ crowning“, depending on density of suspended
material, canopy height, canopy continuity, sufficient surface and ladder fires in order to
reach crowns.
·
How do fires propagate?
- radiation: radiant energy by electromagnetic waves, decreases with the square
distance from heat source
- convection: direct movement of gas/liquid(heated air) flames to ignite fuel; hot air
moves vertically from one molecule to another
- conduction: transfer of heat from one molecule to another. ex: burning embers: burning
embers called “fire brands” are carried with wind and then deposited
·
What factors influence fire propagation
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- type of fuel (wood e.g. oak vs. pine)
- topography (upslope due to hot air get less dense and rise)
- weather conditions (dry->low fuel moisture, wind conditions)
·
What is a spot fire?
- a fire ignited outside of a burn unit as a result of a windborne ember (sometimes
referred to as a firebrand)
· Review risk management: hazards, assessment, mitigation
Risk Assessment and Warnings
· Assessing and monitoring of components (vegetation, topography, weather patterns,
wind direction, moisture)
· Modelling fire potential
Mitigation
· Fire Suppression by forest management policy (incl. Prescribed burns)
· Fighting wildfires (smoke jumpers, firelines, burnout)
· Protecting homes (building materials, clear fuel)
· Evacuations
· Policies
· Mitigation of erosion: can not be prevented, plant vegetation to prevent influence of
rain and run off, straw to minimize overland flow for less slope erosion, felling dead
trees, artificial water drains, plastic sheets
Winter hazards:
Have a rough idea (textbook) how snow flakes form (why different shapes?) and
about the composition of snow (density).
how do snow flakes form?
when an extremely cold water droplet freezes onto a pollen or dust particle in the sky
this creates an ice crystal, as the ice crystal falls to the ground, water vapour freezes
onto the primary crystal building new crystals (six arms of snowflake)
shape depends on air mass, moisture, temperature of air & difference in mobility &
accumulation (packing)
fresh snow = powdery & fluffy (10% density of water thus less air bubbles)
w/ accumulation the snow becomes 30% dense
is this a type of crystal? -->firn = accumulation over a year & we have 50% the density of water (its another
type of snow, basically left over snow that didn’t melt b/c it was so tightly packed together) thx
What does the term “wind chill” describe? Why is it dangerous?
Wind-chill or windchill, (popularly wind chill factor) is the perceived decrease in air
temperature felt by the body on exposed skin due to the flow of air. Your exposed
skin will become more susceptible to frostbite, pneumonia, hypothermia and even death.
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How does freezing rain form? What is supercooled water? Why is it dangerous?
Freezing rain is the name given to rain that falls when surface temperatures are below
freezing. Unlike a mixture of rain and snow, ice pellets (both of which are sometimes
called "sleet"), or hail, freezing rain is made entirely of liquid droplets. The raindrops
become supercooled (the temperature is below its freezing point yet it still remains a
liquid) while passing through a sub-freezing layer of air many hundreds of feet above the
earth, and then freeze upon impact with any surface they encounter.
A storm that produces a significant thickness of glaze ice from freezing rain is often referred
to as an ice storm. Freezing rain is notorious for causing travel problems on roadways,
breaking tree limbs, and downing power lines. It is also known for being extremely
dangerous to aircrafts since the ice can effectively 'remould' the shape of the airfoil and
flight control surfaces.
Describe the lake effect.
Lake-effect snow is produced during cooler atmospheric conditions when cold winds move
across long expanses of warmer lake water, providing energy and picking up water
vapor, which freezes and is deposited on the leeward shores.
What are typical conditions for a snow storm vs. blizzard vs. white out?
Blowing snow with winds greater than 40 km/h are classified as a blizzard. The most
extreme form of blizzard is known as a white-out. This is when the snow is so heavy that
it becomes impossible to distinguish the ground from the air.
BLIZZARD: -25 degrees celsius, >40km/hr winds, <1km of visibility,
Snow storm + strong downdrafts = white out
Name typical hazards for each storm type.
White-out most common hazards: cars getting stuck on road, ships running aground and
sinking, property damage, power outages, loss of income, snow removal and damage
costs, etc.
- Very low visibility and temperatures
- Problems with infrastructure, transportation, power lines, etc.
- Economic loss - people can’t go to work, less production in the industry because factories
are shut down
Name the three types of snow avalanches and what are the differences between
them?
1. Powder Avalanche - Powdery/granular snow, Loose turbulent flow, 20-40 degree slopes,
20-70m/sec.
2. Hard-Slab Avalanche - Block/slab of snow, Most common, accumulation of older snow,
80km/h -> slower than powder, greater volume, heavy.
3. Wet-Slab Avalanche - Water in pore space/ slab separation. Air temp 0 degrees Celsius,
Sunny conditions, softening of snow, almost spherical particles, lower friction, added
weight, 15-60 km/h, slowest avalanche, complex flow, debris.
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Which one is the supposedly least dangerous one for a human caught in it? Why?
The powder avalanche is the least dangerous as the snow is not packed tightly and you can
usually climb out. If you are stuck under the snow you will likely survive longer because
there is more air space for oxygen and it will not be as heavy overtop of you.
What factors promote avalanches?
The factors are: terrain, weather, and snowpack. These categories include things such as
slope steepness, water content, temperature, slope orientation, wind speed and
direction, vegetation, etc.
Promoting factors: Weight, Warm temperatures (weak layer formation), Intermediate slope angle
(too steep=not enough snow deposition)
Name the four main groups of avalanche mitigation processes (defense) and some
examples.
1) Forecasting (risk ID)
2) Monitoring (stability)
3) Mitigation
- active (explosive)
- passive (structural)
- social (awareness)
4) Response and recovery plans
- In case of an emergency there have to be some trained rescue people available
Passive mitigation = Try to reduce avalanche risk by trapping and redistributing snow
with fences. Building roofs over roads so that snow goes over and does not take out the
roads.
Active mitigation = explosions.
Social mitigation = awareness. Bring a shovel and beeper (signal) when skiing
People are trained for how to find people and not to trigger avalanches- also to get out of
an avalanche (Response and recovery). Avalanche warnings (check weather) and signs
–monitor it everyday (stability)
How can sea ice and icebergs be hazards?
They can be dangerous to ships. Like icebergs, but less so, sea ice can be a hazard to
offshore structures, fishing and navigation. It can be either fast ice, which stays close to
shore, or drift ice, which moves around and grinds together with great force to form
ridges.
Are there any positive aspects of winter and ice? If yes explain.
Yes, Snow reflects more heat because its albedo is higher. This allows our planet to help
counteract the global warming that is occurring. It helps keep our temperature a few
degrees lower.
Can use the freezing over of water to access inaccessible locations such as diamond mines
Snow blankets allow for insulation of soil/plants & animals underneath during winter such as
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in Russia
Melting snow recharges streams, reservoirs, groundwater
Snow can be used for agriculture
Natural Disaster – Forecast to Mitigation
& Limitations (Risk Management):
· Define risk, natural hazard, natural disaster, and catastrophe.
Risk
· The product of the probability of a hazard resulting in an adverse event, multiplied by
the severity of the event (insurance: recurrence interval & expected costs)
Natural Hazard
· Natural process which poses threat to human life/property
Natural Disaster
· Natural event that causes significant damage to life/property
Catastrophe
· Natural event that kills or injures large numbers of people or causes major property
damage
·
What are geohazards vs. hydrological/meteorological/climate hazards (as we used
it in this lecture)? Did the number of events of each group decrease/increase over
time? What’s might make a difference?
Geological Hazards
· Hazards driven by geological (i.e., Earth) processes, in particular, plate tectonics
Hydrological Hazards
· Events driven by hydrological (i.e., water) processes. This includes floods, mass
movements.
Meteorological-Climate Hazards
· Driven by meteorological (i.e., weather) processes and climate, in particular those
related to temperature and wind.
· This includes heat waves, cold waves, storms, cyclones, hurricanes, and freezing
rain, wild fires, droughts
Meteorological-Climate and Hydrological are generally increasing in prevalence, while
Geological Hazards are remaining steady
Why are predictions and forecasts of natural hazards still a problem these days?
Technology is not advanced enough to give adequate time for prediction of natural
hazards. Yeah can’t think of anything else.
Are there any interrelations between individual natural hazards?
- many interrelations exist between individual natural hazards
e.g. plate tectonics set off earthquakes which set off tsunamis and landslides
plate tectonics set off volcanic eruptions which set off landslides, floods, Tsunamis and
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weather/climate changes
plate tectonics can set off landslides directly
·
Where do natural hazards occur? And why is that so?
· They occur wherever a threat to human life is possible.
· We like to believe that we can control nature
o We tend to place ourselves in situations that are more susceptible to natural
hazards for a variety of reasons
- We feel we have a right to live where we want
- Not enough natural disaster education. Oh yeah, you tell em.
- We tend to rebuild what we had before a natural disaster occurs, without
taking better precautions the second time around
- We misinterpret long-term variability of natural disasters
·
Why is the number of deaths so high hydrological/meteorological/climate vs.
geohazards?
- With geohazards, high risk areas are known and proper preparations/precautions have
been taken to prevent deaths and damages from those events. However,
hydrological/meteorological/climate based hazards are less easy to predict (high vs low
risk), occur with less frequency, and are often more severe. Because of their low
frequency, they are hard to prepare for, leaving people unprepared, which increases risk
of damages and deaths.
Why is the economic loss due to windstorms, floods and earthquakes so high?
- Windstorms, Floods and Earthquakes are unpredictable, making damages during them
high. Also, because of improper land-use, people tend to build in areas that are high-risk
for flooding and earthquakes, increasing the damages that occur during these events.
What are the three components of risk analysis (explain terms) and why is a proper
risk analysis so important?
- Hazard:
- Exposure:
- Vulnerability-Coping Capacity:
This is important since it is a way of preparing a community by employing measures to
minimize impacts, and preparing them to cope with impacts.
What different approaches are there for risk mitigation? Which approach is favorable
and why? Which approach was chosen earlier and why?
Proactive is before the event occurs, Reactive is after the event has occurred. The
government and other institutions have increased the amount of Proactive methods used
to help minimize the risk in the first place which is more favourable. In the past the
government was mostly relying on reactive approaches.
·
Name the stages of risk management as mentioned in the lecture and what is the
main goal. The first two stages facilitate education and information collection, needed
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for the third stage.
- risk analysis:
- hazard analysis
- exposure analysis
- vulnerability analysis
- socio-economic assessment
- risk assessment:
- evaluation of resilience, coping and adaptive capacity
- tolerable/acceptable risks
- risk communication
- mitigation processes:
- warning systems
- public participation
- planning and policy
- post disaster activities
- emergency management
·
Why is more research needed? To improve records and identify high risk areas
·
After what you learned during this term, is our ability to forecast, predict or
mitigate the same across all types of natural hazards? Yes/No – explain.
no- forecasting/prediction is dependent on many things e.g. technology available and variety
of factors that influence the probability of an event occurring. For example, prediction of
tsunamis is based on the occurrence of an earthquake and calculations regarding the
probability of the resultant waves causing damage. Although we know where they are
likely to occur, it is difficult to predict events like earthquakes ahead of time.
**see slide 10 of ppt
·
Which are the typical problems that have to be addressed in the future concerning
risk management?
Hazard:
● lack of knowledge
● complexity
Relief and recovery:
● inaccessibility, transportation and communication
● tasks and responsibilities
Communities and population:
● Low literacy, low awareness and knowledge
● preparedness
● skepticism
Mitigation measures (government, policies, and engineering)
● costs
●
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●
●
●
short-term solution
policy/guideline
effects
Earth Science 2GG3 - General Notes and
Quiz Questions
Test Quiz
Q: Heat Within the Earth comes from ________
A: All answers are right.
Q: What does the oceanic lithosphere consist of?
A: Basalt on top gabbro, followed by peridotite.
Q: When is a large event such as a major earthquake NOT a disaster?
A: When it happens in an area without any people
Q: Which of the following is true?
A: Earth’s crust is less dense than the mantle.
Q: Where do asteroids originate in space?
A: They originate in the belt between Mars and Jupiter.
Q: How is the tail of a comet oriented? (Which way does it point?)
A: Points away from the sun.
Q: How fast do comets travel in space?
A: About 60 km per second
Q: Which of the following would NOT result from impact of a large asteroid on Earth?
A: High radioactivity in the crater
Q: What are comets made of?
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A: ice and some rock
Q: A smaller rock that enter Earth’s atmosphere and survives to reach the ground is
a(n)?
A: meteorite
Q: What is the Earth’s inner core made up of?
A: Iron and nickel
Q: The boundary that separates the crust from the mantle is called?
A: the Moho.. ISnt the answer LVZ? Moho is difference between crust and
lithospheric mantle (which is different from “the mantle”.
Q: The S-wave shadow zone is evidence that _____
A: the outer core is liquid
Q: The current hypothesis for the origin of the moon is that _____
A: by accretion of fragments and vapor generated when a Mars-sized body
collided with the Earth
Q: When seismic waves pass across the boundary between two different material,
______
A: All of the above
Q: The Earth, unlike the Moon, has few obvious impact craters because ______
A: The Earth is an active and dynamic planet whose surface is constantly
undergoing change e.g. plate tectonics
Q: The most common type of meteorites discovered on Earth is ____A: chondrites
Q: The cluster of millions of asteroids situated between Mars and Jupiter is called _____
A: Asteroid Belt
Q: Which of the following is not a known or suspected impact site?
A: Gubbio, Italy
Q: Evidence of a major impact at the K/T boundary (65 million years ago) includes
A: iridium & shattered quartz in the K/T-age sedimentary rocks
Q: Energy released by a meteorite impact is largely a function of _____
A: mass and velocity
Q: The expected rate of impact of a space-debris fragment 1 km in diameter worldwide is
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about ______
A: One per million years
Q: A disaster is defined according to ____
A: Its consequences for humans
Q: As the magnitude of a natural disaster increases their frequency of occurrence _____
A: decreases
Q: What process is thought to have produced the Earth’s core?
A: density separation
the top surface of the rocky crust will _____.
b) move downward
13) The Earth's internal heat is responsible for causing______.
a) movement of lithospheric plates
14) The rigid tectonic plates float on ______ .
d) the plastic asthenosphere
15) In the concept of plate tectonics the term "plates" ref
Quiz #1
1) What is the normal relationship between the number of a particular type of event and
the size of such an event?
a) There are many small events, a moderate number of larger events, and few giant
events of any given type.
2) Before people understood plate tectonics, what evidence led some scientists to
believe in continental drift?
a) Fossils match across the Atlantic Ocean.
3) The magnetic stripes of the seafloor are considered evidence of seafloor spreading
and _____?
d) periodic reversals in the polarity of Earth's magnetic field
4) How fast do asteroids travel in space?
c) about 15 to 25 km per second
5) A Chondrite consists of______?
b) peridotite like the Earth's mantle
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6) What is the name of the supercontinent which was formed by Wegener's proposed
continental drift?
c) Pangaea
7) Approximately how many major lithospheric plates are there?
a) about 12
8) Which of the following increases with distance from a mid-ocean ridge?
d) all the above
9) Which of the following is true?
d) all the above
10) Where do comets originate in space?
c) the Kuiper Belt
11) Which types of seismic waves are generated by an earthquake?
d) all the above
12) The concept of isostasy states that the "plastic" asthenosphere will adjust to the
addition or removal of mass on the Earth's crust. If North America were to become
covered in several kilometers of ice as during the last Ice Age, we can hypothesize that
ers to the _____ .
a) the rigid Earth above the asthensophere
16) Which region makes up over 80% of the volume of our Earth?
d) the mantle
17) Which of the following statements is false?
b) the P-wave shadow zone is larger than the S-wave shadow zone.
18) The S-wave shadow zone is caused by the ____
a) Outer Core
19) What is a hazard?
d) a natural process which poses threat to human life and property
20) Which of the following statements about the low-velocity zone is right?
b) this zone marks the boundary between the lithosphere and the mantle
21) What drives plate tectonics?
c) thermal convection
22) Where is the Earth's magnetic field generated?
b) in the outer core
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23) Which of the following rock types would be most likely to record the magnetic field at
the time the rock formed?
c) a basaltic lava flow
24) Which of the following term associations is FALSE?
d) outer core - rigid solid
25) A cooling magnetic material __________ its magnetic character as its Curie
temperature.
b) gains - this is correct
Quiz 2:
1. New oceanic lithosphere forms at - divergent plate boundaries
2.The Hawaiian Islands formed at a - none of these I know they don’t ask but for study
purposes does anyone know what the answer is if not none of those options?
I believe it is because they are formed at a hot spot not a boundary
Can confirm this is correct; yes I believe you are correct, they formed as a hotspot
punctured through a moving plate
3. Shearing stresses and shallow earthquakes are associated with- transform
boundaries.
4. Volcanic eruptions can affect the climate because - volcanic dust and gas in the upper
atmosphere reflect and absorb solar radiation
5. Magma with a high silica content tends to be - very viscous
6. Which type of volcano is NOT commonly composed of basalt? - Composite volcano
7. Which of the following describes the build up and release of stress during an
earthquake? -Elastic Rebound
8. The point where movement occured which triggered the earthquake is the _____. The
hypocenter
9. How do rock particles move during the passage of a P wave through the rock? - Back
and forth parallel to the direction of wave propagation.
10. Which types of faulting would be LEAST LIKELY to occur along the Mid Atlantic
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Ridge? - Reverse
11.Surface waves consist of the - None of that shit
12. Where is the hypocenter with respect to the epicenter? - Directly Below the epicenter
13. Basaltic magmas poor in silica are generated mostly by the melting of ______ and
are erupted mostly as ______ - asthenosphere, lava flows
14. When a volcanic cone collapses into its magma reservoir it forms a ______ - Caldera
15.The East coast of North America represents a ____? The east coast of North America
is not a plate boundary
16. The fastest seismic waves are: P waves
17. Which of the following regions have a significant seismic hazard risk? California
18. Magma production takes place at ___. All of these.
19. Hotspots under continental lithosphere generally generate ___, while those under
oceanic lithosphere commonly create____. Calderas, shield volcanoes
20. Earthquakes are associated with ____. All of these
21. Which of the following can be triggered by an earthquake? All of these.
22. Which of the following statements best describes the state of earthquake prediction?
Scientists can characterize the seismic risk of an area, but can not yet accurately predict
most earthquakes.
23. Which set of the waves on the seismogram are probably the surface waves? C
what is C? > it’s a point on the graph.
24. Which of the following factors helps to determine whether a volcanic eruption will be
violent or relatively peaceful? All of these
25. The asthenosphere is _____. the source of most magmas.
Quiz 3
1. Where does the warm front form?
warm air moves over cold air and replaces it
2. what is an area in which two or more air masses meet?
occluded front
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3. which of the following is a cause of the changes in season
tilt of the earth’s axis
4. Where does a cold front form?
where cold air moves under warm air
5. what is a cloud made of?
water droplets or tiny ice crystals
6. why does the equator experience high temperatures year round
the sun’s rays hit it directly
7. when droplets in a cloud reach a certain size and abundance, they
fall as precipitation
8. Changes in weather are caused by interactions of
air masses
9. Milankovitch theory is based on 3 cyclical alterations in the earth’s orbit around
the sun, which of the following is not one of these cycles?
equatorial gradient
10. Which of the following statements is true?
warm water - lower salinity - lower density - surface water
11. What does El Nino Involve?
warmer surface water moves Eastward in the equatorial regions of the
pacific
-who’s this South American boy though...loll <BAHAHA Baby Jesus
obviously
12. Air pressure is greater
at the Earth’s surface
13. In order to equalize air pressure imbalances, air moves from
High pressure to low pressure
14. Which statement about air pressure is correct?
lateral differences in the air pressure causes winds
15. Rather than flowing in a straight line from polar region to the equator, winds
are deflected due to the
Coriolis effect
16. Orographic precipitation is caused by
warm moist air rising over a physical obstruction such as a mountain range
17. What is a hydrologic cycle?
“The hydrologic cycle shows
how a small but important part
of water from the vast oceans
evaporates to cycle through
clouds and precipitation to feed
lakes and streams, vegetation,
and groundwater, before much
of it again reaches the oceans.”
-textbook
Water moving between the
atmosphere, the land, and the
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ocean
18. What does the term Westerlies mean?
Winds in the middle latitudes which blow from West to East
19. The most abundant gases in the Earth’s atmosphere by volume are
nitrogen and oxygen
20. The higher the albedo, the ___ a surface ____
more, reflects
21. The uneven heating by solar radiation produces
Weather
22. Cold air sinks because ___
it is more dense
23.A huge body of air that has similar temperature, humidity and air pressure
air mass
24. _____ are the clouds which have the greatest vertical extend
Cumulonimbus
25. What does the term Thermohaline Circulation mean?
Global water fluxes due to gradients in temperature, salinity and density
--------------------------------------Quiz 4
1. Which of the following is NOT a characteristic of lightning?
a) Lighting is a form of static electricity
b) The visible flash of lightning typically travels from the ground to the cloud
c) Lightning is a form of alternating current
d) Lightning forms as a result of charge separation
2. Which of the following is important to the formation of lightning in a developing cloud
strong vertical air currents
3. Hurricanes, tornadoes, and middlelatitutu cyclones are similar in that they _____.
area areas of low pressure
4. The Fujita Intensity Scale is commonly used to assess _____ intensity.
tornado
5. Atmospheric circulation in the immediate vicinity of a thunderstorm is _____.
cyclonic
6. Thunder will not occur ______.
a) Without lightning
b) in wintertime storms when it is too cold
c) until precipitation begins to fall from the clouds
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d) over the ocean or large lakes
7. The strongest winds and heaviest are associated with which part of a hurricane?
The eye wall
8. On average, which ocean basin produces the most hurricanes/typhoons/cyclones per
year?
Western North Pacific (near Southeast Asia) where they are called
typhoons.9. Which phenomenon associated with thunderstorms was described in class
as being particularly dangerous for airplane travel and the cause of several airline
crashes?
Plane flying low to the ground near a microburst
10. Which aspect of landfalling hurricanes is usually responsible for the most
destruction?
Storm surge
11. _____ is the typical thunderstorm cloud.
cumulonimbus
12. Atmospheric pressure in the center of a tropical cyclone is _____.
very low because of rising warm air
13. A tropical storm becomes a hurricane and forms an "eye" when wind speeds exceed
____ miles per hour.
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14. Which of the following factors are used to rate the intensity of a hurricane?
wind speed
15. What is the motion of a stick (or a water molecule) in an deep-water wave (open
ocean)?
It moves in a circular motion with the top of the wave moving in the
direction of wave travel
16. What factor does NOT influence the size of most waves?
a) atmospheric pressure
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b) time of wind across water
c) wind velocity
d) fetch
17. How do sand dunes help maintain sand on a beach?
Eroding dune sand spreads over the beach and takes up wave energy.
18. Where does beach sand NOT originate?
a) erosion of sea cliffs
b) streams and rivers
c) longshore drift
d) deeper ocean as much as 100 km offshore
19. What two main factors cause increased height of a storm surge?
low atmospheric pressure and strong hurricane winds
20. The distance from the crest of a wave to the next crest is _____.
the wavelength
21. The movement of sediment parallel to shore when waves strike at an angle is called
______.
longshore drift
22. Which of the following structures can disrupt longshore drift?
a) jetties
b) breakwaters
c) marinas
d) all of the above
23. Which landforms would you expect to find on erosional coasts?
a) sea cliffs
b) rocky headlands
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c) sea stacks
d) all of the above
24. A glacial valley drowned by rising sea-level is called ____.
a fjord
25. A tropical storm or hurricane develops in _____ air.
maritime tropical
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