How do geologic processes change
the shape of Earth’s surface?
What do Earth’s layers consist of?
• Crust
• Mantle
• Core
Crust
• Layer of rock that forms Earth’s “outer
skin”
• Includes rocks, mountains, soil, water
• Thin: 5-40km thick
• 870◦C
2 Types:
• Continental: Dry land (granite)
• Oceanic: Ocean (basalt)
Mantle
• Layer of hot rock
• 2,900km thick
• 2,200◦C
2 Sub layers:
• Lithosphere
• Asthenosphere
Lithosphere
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Rigid
Much like the crust
100km thick
Floats on top of the asthenosphere
Asthenosphere
• Plastic like
• Material can flow slowly like hot tar
• Has both solid & liquid qualities
Core
• Consists of iron & nickel
• 5,000◦C
• Makes up 1/3 of Earth’s mass
2 sub layers:
• Outer Core
• Inner Core
Outer Core
• Layer of molten material
• Covers the inner core
• 2,250km thick
Inner Core
• Dense solid ball of metal
• Extreme pressure does not allow Fe & Ni
to spread out to form liquid
• 1,200km thick
What are the 3 ways that heat is
transferred?
• Radiation
• Conduction
• Convection
Radiation
• Heat transferred by EM waves through
space
• EX: Sitting by the fire!
Conduction
• Heat transferred through direct contact
• EX: Spoon in hot chocolate
Convection
• Heat transferred through a fluid movement
of either a gas or liquid
• EX: Chicken noodle soup heating on the
stove!
Which of these do you think
happens in Earth’s mantle?
• Convection!
• Convection currents flow in the
asthenosphere
• Heated material rises to the top of the
mantle (lithosphere), cools, then sinks
back to the bottom
What does the Theory of
Continental Drift state?
• 1910
• Alfred Wegener hypothesized that all the
continents had once been a single
landmass
• A super continent
called “Pangaea”
Scientific Method
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Problem/Question
Research
Hypothesis
Experiment
Analyze
Conclude
Supporting Evidence of Wegener’s
theory
• Landforms
• Fossils
• Climate
Landforms
• South America & Africa have similar
mountain ranges
• Europe & North America have similar coal
fields
Fossils
• Fossil-any trace of an ancient organism
that has been preserved in rock
• Mesoaurus fossils have been found in
places now separated by oceans
• Glossopteris (fern like plant) fossils have
been in rocks in Africa, South America,
Australia, India, & Antarctica
Climate
• Spitsbergen Island lies in the Arctic
Ocean, north of Norway, covered with ice
• Fossils of tropical plants have been
discovered under the ice!
• South Africa-deep scratches in rock
indicate glacier movement there!!!
REJECTED!!!
• Scientists rejected Wegener’s theory of
continental drift
• Most scientists in the 1900’s believed the
Earth was cooling & shrinking causing the
continents to move & mountains to form
Is sea-floor spreading like
continental drift?
• 1960
• Harry Hess, when studying the mid-ocean
ridge, proposed that the ocean floor
moved like a “conveyer belt” moving the
continents with them
• Sea-floor spreading is the continually
adding to the ocean floor
Sea-floor Spreading
• Molten material rises up from the mantle
• It spreads out, cools off, & hardens
• It pushes the older rock out on both sides
of the ridge
• New crust forms!
Wait a minute…!
• Hess’ idea of sea floor spreading caused
scientists to revisit Wegener’s idea of
continental drift!
So where does all of the old crust
being pushed out go?
• Subduction: It is the process by which the
ocean floor sinks beneath a deep ocean
trench & back into the mantle
Sea Floor Spreading &
Subduction…
• Can change the shape of the oceans!
• The ocean floor is renewed every 200
million years
(That’s the time it takes for new crust to
form, move across the ocean floor, & sink
into a trench)
What is the Theory of Plate
Tectonics?
• 1965
• Tuzo Wilson proposed that the cracks in
Earth’s surface were broken into section
called “plates”
• He combined the idea of sea-floor
spreading, Earth’s plates, &
continental drift into a single
theory
Plate Tectonics Theory
• A geological theory that states that pieces
of Earth’s lithosphere are in constant, slow
motion driven by convection currents in
the mantle
How does it work?
• Lithospheric plates float on top of the
asthenosphere
• Convection currents rise in the
asthenosphere & spread out under the
plates
• No plate can move without affecting
another plate
• Plates move extremely slow at 1-10cm per
year
• As the plates move, collide, or pull
apart…it produces GREAT changes on
Earth’s surface
• Like volcanoes, earthquakes, mountain
ranges, & deep sea trenches
3 types of plate boundaries:
• Transform
• Divergent
• Convergent
Transform
• Place where 2 plates slip past each other
moving in opposite directions
• Earthquakes often occur along these
boundaries
Divergent
• Place where 2 plates move apart
• Most occur at the mid-ocean ridge
• Some occur on land creating a “rift valley”
which is a deep valley
• Great Rift Valley in Africa is 3,000km long
Convergent
• Place where 2 plates come together
• Collisions of 2 plates can cause:
– Oceanic to oceanic
– Oceanic to continental
– Continental to continental
• When 2 plates collide the more dense
plate comes out on top!
• Continental – Continental: mtns form
• Oceanic – Continental: Oceanic dives
under the continent
• Oceanic – Oceanic: the less dense of the
2 sinks into the trench
What is an earthquake?
• Shaking & trembling that results from the
movements of rock beneath Earth’s
surface
• The movement of Earth’s plates creates
stress that squeezes/pulls the rock in the
crust
Stress
• A force that acts on rock to change its
shape & volume
• 3 types of stress
– Shearing
– Tension
– Compression
Shearing
• Stress that pushes a mass of rock in
opposite directions
Tension
• Stress that pulls on the crust stretching the
rock so it becomes thinner in the middle
Compression
• Stress that squeezes rock until it folds or
breaks
What is a fault?
• A break in the crust where slabs of rock
slip past each other
• Faults usually occur along plate
boundaries
• 3 types:
– Strike-slip
– Normal
– Reverse
Strike-Slip Fault
• Rocks on either side of the fault slip past
each other sideways
• Ex: San Andres Fault
Normal Fault
• The fault is at an angle
• One block is above the fault & the other is
below it
• Ex: Rio Grande Rift Valley in New Mexico
Reverse Fault
• Same structure as a normal fault, but the
blocks move in opposite directions
• Ex: Appalachian Mts
Where do earthquakes begin?
• Earthquakes occur in the lithosphere
100km below Earth’s surface
• The focus is point beneath the surface
where the rock broke causing the
earthquake
• The epicenter is the point on the surface
right above the focus
Seismic Waves
• During an earthquake seismic waves race out
from the focus in all directions
• The seismic waves are greatest at the epicenter
• Seismograph is the instrument used to record
ground movement caused by seismic waves
• 3 types:
– P waves
– S waves
– Surface waves
P waves
• Primary Waves
• 1st to arrive
• Compress & expand the ground like an
accordion
S waves
• Secondary Waves
• 2nd to arrive
• Vibrate the ground back & forth
Surface Waves
• Come from P/S waves
• Move slowly
• Can cause the ground to roll like ocean
waves
How do they measure the size of
the quake?
• Magnitude is the measurement of
earthquake strength based on seismic
waves & movement along faults
• 3 ways to measure magnitude:
– Mercalli Scale
– Richter Scale
– Moment Magnitude Scale
Mercalli Scale
• Measures the intensity
• Not precise
Richter Scale
• Rates the size of seismic waves using a
particular seismograph
• Accurate measurements for nearby
earthquakes
Moment Magnitude Scale
• Rates the total energy released by an
earthquake near or far
What types of damage can a quake
cause?
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Damage/destroy buildings
Topple power lines
Break water & gas lines
Cause landslides
Can cause aftershocks days/months later
Can cause tsunamis
Tsunamis
• Large wave that occurs when an
earthquake displaces water in the ocean
What causes volcanoes?
• A volcano is a weak spot in Earth’s crust
where magma comes to the surface
• They form at:
– Divergent boundaries
– Convergent boundaries
– Hot spots
Divergent Boundaries
• Most volcanoes occur here
Ex: Mid-ocean ridge
•Volcanic belts occur along plate boundaries
where lithospheric plates are weak
Ex: Ring of Fire
Ring of Fire
• Major volcanic belt formed by volcanoes
that rim the Pacific Ocean
Convergent Boundaries
•Island Arc-when 2 oceanic plates collide
creating an arc of islands
Ex: Japan, New Zealand, Caribbean
Islands
Hot Spots
• Where magma rises up from the mantle
melting Earth’s crust
• Often occur in the middle of a plate
Ex: Hawaiian Islands, Yellowstone
National Park
How do volcanoes erupt?
• Magma is under extreme pressure in the
mantle
• It bubbles up through cracks in Earth’s
crust
• Pressure decreases as magma nears
Earth’s surface
• Lava bubbles out of the volcano
What does the inside of a volcano
look like?
Magma Chamber
• Where magma is stored under the volcano
Pipe
• Magma moves through this long pipe that
connects the magma chamber to Earth’s
surface
Vent
• Opening where gas and lava leave the volcano
Crater
• Hollowed-out area at the top of a volcano
Volcanic Neck
• Magma that hardens inside the pipe
Dike
• Magma that forces itself “across” rock
Sill
• Magma that squeezes between layers of
rock
Batholith
• A mass of rock formed when a large body
of magma cools inside the crust
What are the different types of
volcanoes?
• Shield Cone
• Cinder Cone
• Composite
Shield Cone Volcano
Cinder Cone Volcano
Composite Volcano
Volcanoes in the US
Mt. Hood
Mt. St Helens
Mt. Kilauea
What are the stages a volcano
goes through?
• Active→Dormant→Extinct
Active
• It’s alive!
• It is erupting or shows signs of erupting
Dormant
• It’s sleeping…
• It is expected to become active in the near
future
Extinct
• Dead as a door nail.
• Unlikely to erupt again
The End!!!
Sike…this is the end!