Surface Processes: Mass Wasting
Mass Wasting can be defined as:
“the movement of earth materials down slope primarily under the
influence of gravity.”
I. Characteristics and examples:
 Steep slopes are especially vulnerable due to the high
gradient.
 All forms of mass wasting cause the deaths of many people
around the world, and billions of dollars of damage every
year.
 Houses built near the edge or out over a cliff can be
destroyed when the cliff collapses.
 A ditch dug in a hillside for irrigation can cause the hillside to
slide downhill.
 Springtime snow-melts can cause soils to saturate causing
landslides and mudflows.
II. Factors Controlling Mass Wasting:
A. Steepness of Slope–
 Rocks and soils are less likely to slide down slope in
gentle or flat terrains. The angle of repose is the angle,
that if surpassed by piling on more particles, causes the
pile to slide.
B. The Lithology and Orientation of Rock Layers  Shear strength is the resistance of a material to being
pulled apart.
 The shear strength of a slope is relative to the type of rocks
(lithology) and their orientation to the slope. If the rock
strata dip in the same direction as the slope, the upper
layers are prone to slide down slope over time.
 If rock layers dip into the hillside the rock cannot slide along
the bedding planes and the slope is likely to remain stable.
 Processes that determine a slope are proximity of streams,
rivers, or ocean waves, road cuts or other types of
excavation.
C. The Nature of Unconsolidated Materials
 The Angle of Repose is the maximum slope angle at which
loose materials remain stable.
 Each particle size (sand, pebble, cobble, etc.) has its own
angle of repose.
D. The Role of Climate and Vegetation
 Shear strength and angle of repose are not constant but vary
with different conditions.
 The amount of water present in loose materials affects its
stability and adds weight to the soil.
 Water’s polarity permits it to bind to other substances by
electrical attraction
 When there is a moderate amount of water in the soil, water
molecules form a film around the grains and hold them
together with only electrical forces.
 Too much water then begins to push the particles apart
causing them to flow.
 The roots of plants hold the soil together and therefore, a
highly vegetated slope is more stable than a similar but bare
slope.
 Bare, steep areas with lots of rainfall are prone to mudflows
and slides (some deserts are good examples of this type of
terrain).
E.
The Relief of the Slope
 The relief of the slope pertains to the vertical distance
between the top of a hill or mountain and the bottom of the
valley floor.
 If the relief is great, the particles will have a tendency to
move down slope.
F. The Activity of Earthquakes or Volcanoes
 If a shock occurs in an area of instability, the slope may be
shaken loose creating slides and flows.
III. Types of Mass Wasting:
A. Flow - Loose, unconsolidated materials moving down slope
as a viscous liquid are called flows. They can be slow or moderately
fast. Examples include:
Creep - the slow downhill movement of rock or soil.
 Creep movement is typically so slow that motion cannot be
detected without a reference point.
 The surface moves more rapidly than the deeper layers.
 This causes buildings, fences, telephone poles, roads, etc.,
to be affected.
 Creep is common in areas with series of weather related
freeze-thaw cycles.
Debris Flow, Earthflow, and Mudflow –Different types of flows
are characterized by the sizes of the solid particles:
 Debris Flow – consists of a mixture of sand, silt, clay, and
rock fragments. These occur in arid or semi-arid areas
where slopes become overloaded with moisture following
heavy rains.
 Earthflows and Mudflows – are mass movements of
predominately fine-grained soil particles mixed with water.
Earthflows have less water than mudflows. All of these types
of flow can occur whenever volcanic activity melts the glacial
ice near the summit of volcanic mountains.
 Solifluction is the upward expulsion of large rocks, buried
logs, or caskets (insome cases) due to the soil being oversaturated for periods of time. Examples include areas of
permafrost subjected to seasonal thaws, or deltaic
environments such as New Orleans.
B. Slide – This is when large blocks of rock or soil fractures
and moves as a unit. Examples include:
 Slump – When a gently arching, concave fracture forms in a
rock layer or regolith. Big blocks of rock and soil move down
slope. Many times these events are accompanied by types
of flow.
 Rockslide or Rock Avalanche – is a type of slide in which
a segment of bedrock slides along a tilted bedding plane or
fracture.
C. Fall – A rock may become dislodged from a steep cliff, and
falls or tumbles downward rapidly under the influence of
gravity. These are common in mountainous areas subjected
to freeze-thaw cycles (especially when frost wedging is in
action).
IV. Some Case Histories of Mass Wasting:
1. Madison River Slide, Montana, 1959: In August of 1959, an
earthquake west of Yellowstone National Park triggered a massive
rockslide where 30 million cubic meters of rock broke loose and slid
into the valley below. Intense winds were generated as air escaped
from beneath the debris. The debris fell into the Madison river moving
water quickly downstream drowning some people. The debris also
formed a natural dam.
2. Yungay, Peru – In 1970 an earthquake shook loose an 800
meter wide slab of ice from a glacier near the top of Mt. Huascaran.
The ice hit a pile of loose, unconsolidated regolith causing a massive
slide down slope. The air trapped under the slide escaped at velocities
in excess of 400km/hr. When it reached a heavily populated valley, it
jumped over a ridge and completely buried the town of Yungay, Peru,
killing approximately 17,000 people.
3. Nevado del Ruiz – Colombia, South America. In November of
1985, the volcano Nevado del Ruiz erupted in central Colombia. The
heat from the eruption melted large quantities of ice and snow forming
a massive mudflow, killing and burying 20,000 people in the valley
below.
V. Lessons Learned:
Mass wasting occurs commonly in the same region or even precisely
in the same location. Human deaths and property damage can be
averted by the proper planning of governmental agencies. That is why
governmental agencies from city level to state and national
organizations make use of geologists in civic planning.
Rivers and Streams
I. The Hydrologic Cycle:
This is the cyclic nature of water whereby oceanic water (as well
as large freshwater bodies i.e. Great Lakes) is evaporated by the heat
of the sun. This free water vapor collects in the form of clouds, moves
in the air currents, cools as it moves over land, and releases
"meteoric" water, or precipitation. This surface water runoff
eventually makes its way back to the sea in the form of streams and
rivers, whereby it is again converted into water vapor by the sun, etc.,
and the cycle continues.
II. Major Processes of the Hydrologic Cycle:
1. Evaporation - the transformation of a liquid (water) into a gas
(water vapor)
2. Transpiration – the loss of (evaporation of) water vapor from
the leaves of plants
3. Precipitation – all processes in which the atmospheric
moisture returns to the Earth’s surface
4. Runoff – the term for the water that flows back to the oceans
over the surface of the land
III. Occurrence of Water:
 About 75% of the earth’s surface is covered with water with
an average depth of 5000 meters.
 97.2% of the free water on earth is in the oceans (saltwater).
 2.8% is all other water (freshwater and ice). Of this 2.8%:
2.15% - land ice (glaciers)
0.625% - groundwater
0.017% - lakes
0.001% - atmospheric water vapor
0.0001% - streams
IV. Streams:
General characteristics:
1. Sheet flood occurs after the soil has become saturated and
the water flows over the surface in broad, thin sheets.
2. Within a short distance the water begins to collect into tiny
channels called rills.
3. Rills collect into larger “streams” that may be a gully, ditch, etc.
4. A “stream” is a body of water that flows in channels and is fed
by many smaller streams called tributaries.
5. During normal flow, the stream is confined to a well-defined
channel.
6. The floor of the channel is called the bed.
7. The rising slopes bordering the channel are the banks.
8. During a flood, streams overflow their banks and water covers
the adjacent land called the floodplain.
9. The flood plain is usually bounded on either side by the valley
wall.
V. Stream Flow:
1. Laminar flow occurs when the water flows in straight, even
paths.
2. Turbulent flow occurs whenever the flow lines become
irregular and chaotic, usually due to obstructions in the stream
bed.
3. The three factors of stream flow are
a. the gradient of the stream bed that is expressed as
the vertical drop of the stream over a specific distance.
b. the flow or discharge of the stream that is the
volume of water flowing downstream per unit time. This is
usually expressed in cubic meters per second. Discharge is
expressed as: (m3/sec) = channel width (m) x channel depth
(m) x velocity (m/sec)
c. the shape of the channel…When water flows
downstream it is slowed by friction between the moving water
and the stream bed and banks. In straight streams, the center
of the stream flows most rapidly. The total friction depends
upon the size, the shape, the channel roughness, and
obstructions in the stream channel.
VI. Stream Erosion, Transport, and Deposition of Sediments:
A. Stream Erosion General characteristics:
 Different stream velocities are required to erode different size
particles.
 More energy and higher current speeds are required to erode
sand grains than to keep them moving once they have been
picked up by flowing water.
 Erosion occurs at high stream velocities and sediment is
deposited at lower stream velocities.
 Sand-sized particles are most easily eroded.
1. Hydraulic Action – the ability of moving water, by itself, to
dislodge pieces of rock and grains of sediment. Different
stream velocities are required to erode different sized particles.
Hydraulic Plucking is the process of the stream picking up a
rock or particle due to the physical property of there being
lower pressure in the middle of a flowing stream relative to the
surrounding water. The term describing a particle bouncing
along the bottom of a stream due to this action is called
saltation.
2. Abrasion – When sediment is transported by flowing water, the
grains strike each other, the banks, and the bed of the stream.
This action breaks off small pieces of material from the
sediment particle and whatever it strikes.
3. Potholes – Sediments striking the streambed can dig out
depressions that, when deep enough, allow larger particles to
fall into and not escape. As subsequent water flowing over the
depression tries to hydraulically pluck the sediments out, the
particles swirl around “drilling” the depression deeper until a
pothole is formed.
4. Lateral Erosion – the sideward erosion of a steam resulting in
a widening of the stream valley. (see cut-bank and point bar
notes)
5. Head ward Erosion – the process of a stream eroding
upstream into its gradient. Bed load traction in the headwaters
of a stream is a good example of this. (see stream terracing)
B. Transportation  Stream Competence – is the measure of the largest particles
that the stream can carry.
 Stream Capacity – is the maximum quantity of sediment that a
stream can carry. Both competence and capacity of a stream are
directly related to stream discharge.
 Types of loads carried by streams are:
1. Dissolved Load – the dissolved substances a stream carries.
This is dependent upon stream water chemistry, not velocity or
discharge. If the stream is carrying dissolved salts, after floods,
the soils may develop an increase in salts after the water
evaporates. This process is called salinization.
2. Suspended Load – a physical mixture of water and small
particles. A high suspended load causes the water to become
cloudy or turbid. Turbidity (clarity of the water) is directly
related to the amount of suspended load a stream is carrying.
3. Bed Load – This describes all of the large particles transported
on or immediately above the streambed. If the particles are
dragged or rolled (hydraulic plucking) along the streambed,
the motion is called traction. The action of erosion by traction
C. Deposition When the stream current slows down, the competence and
capacity of the stream also reduces. Particles are then deposited with
the largest particle falling to the bed first, and the finest particles falling
out last.
Channel Deposits:
1. Bar – an elongated mound of sediment in a stream channel
2. Meander – As the gradient of a stream decreases, the shape of
the stream changes from being straight in the highlands to “S”-
shaped on flat areas (i.e. coastal plains). These “S”-shaped
bends that indicate a flat terrain are called meanders.
3. Cutbank – the outside curve of a meander where currents are
usually faster, and more lateral erosion occurs.
4. Point bar – On the inside curve of the meander, the currents are
slower and deposition occurs. These deposits form what are
called point bars opposite the cutbank.
5. Oxbow Lake – Sometimes as erosion continues the meanders
may become so pronounced that the side of one curve will
approach another creating a new channel and forming an oxbow
lake…the abandoned curve of an old meander.
6. Mid-channel Bar – As a tributary joins a stream forming a “Y”shaped junction, the low energy portion is at the intersection
(point) of the two streams causing a mid-channel bar to form.
7. Braided Stream – is one that flows in an interconnecting network
of many shallow channels separated by low islands and minchannel bars. These develop where the amount of sediment is
greater than the stream can transport and are common in both
deserts and glacial areas.
Alluvial Fans and Deltas Deposit:
 When a stream flows from a mountain front onto a flat plain,
its velocity decreases. Particles of all sizes are deposited in
a large, fan-shaped landform called an Alluvial Fan.
 Stream currents slow dramatically when they enter a lake or
ocean. As the current slows down, sediment is deposited
forming a nearly flat plain called a Delta. As the delta grows,
the stream splits into many channels called distributaries.
At the outer edge of the delta sediments slide into deeper
water forming deposits that are not horizontal to the plain of
the delta. Many times they are nearly vertical. As these
Foreset Delta deposits extend outward, other horizontal
deposits are lain upon these foreset deposits. These are
called the Topset Deposits.
Floods and Floodplain Deposit:
Discussion:
 Mountain and desert streams often flood as a result of sudden,
intense thundershowers.
 Intermittent streams are those that transport water only during
rainfall. During dry times, the channels may become clogged with
debris such as tree branches, rocks, etc. During a storm these
obstructions form temporary dams that can suddenly break
releasing a large amount of water downstream. This is an
example of a flashflood.
 Flashfloods may also occur in areas that have received a large
amount of rainfall and then receives another large amount of
rainfall in a short period of time, not allowing the first waters to
drain away.
 The portion of land covered by water during a flood is called the
flood plain.
 When a stream overflows its banks ( the stream “crests”), the
coarsest material is deposited on the banks of the stream forming
a natural levee.
Downcutting and Base Levels:
 Downward erosion is a process called Downcutting.
 The Base Level of a stream is the deepest level to which it can
erode.
 The Ultimate Base Level is the sea.
 Local or Temporary Base Levels occur along a stream in the
form of lakes and waterfalls.
 Over time, erosion and deposition even out irregularities in the
gradient of a stream producing a Graded Stream.
 An idealized graded stream is in equilibrium with its sediment bed.
 Stream profiles can be altered artificially by the construction of
dams.
 A Stream Terrace is an abandoned floodplain of a once base
level of a stream. This gives a mountainside a “stair-step”
appearance, with each “step” being an old terrace.
Formation of Valleys:
A Peneplain is a large featureless plain…A land surface worn down by
erosion to a nearly flat or broadly undulating plain. This represents the
penultimate stage of old age of a once mountain range or series of
once hilly areas. Such a surface may be uplifted again by tectonic
forces forming a plateau or highlands that once again can be subjected
to surface erosion forming valleys, canyons, etc.
Incised Meanders (or “Goosenecks”) may form whenever a
meandering stream flowing over a peneplain begins to cut downward
as the peneplain is uplifted. An example of this is the Goosenecks of
the Gunnison in Colorado.
An Antecedent Stream is one in which the uplift of the surrounding
land is slow enough that the stream cuts through the rising bedrock
maintaining its original level. Antecedent streams existed before the
uplift (i.e. mountain uplift) occurred.
Stream Piracy is where one steam “steals” water from another by the
first stream’s headward erosion or lateral erosion breeching into the
drainage basin of another stream. The stream that is losing water may
cease to exist.
1. Valley Shape and Mass Wasting – Mass wasting occurs along
all streams. As a stream cuts downward, the sides of the valley
may be eroded and the valley widened by mass wasting,
sheetflood, or other forms of surface erosion.
2. Lateral Erosion – As a stream approaches a graded condition
the channel will migrate widening the valley. Mass wasting of the
valley wall is the major factor widening the stream valley.
3. Valley Shape – “V”-shaped valleys are relatively straight and
steep-sided channels. Downcutting is predominant. Closer to
base level lateral erosion and mass wasting are predominant
forming wider valleys.
Drainage Basins:
 Any two adjacent river systems separated by raised areas of
land are in different drainage divides. This is seen in rivers
such as the Brazos compared to the Colorado…both are in
separate drainage areas that are separated by raised land
areas.
 A region that is drained by a single river is called a drainage
basin…the Brazos drainage basin, the Colorado drainage
basin, etc.
 River Authorities, such as the Lower Colorado River
Authority, are governmental agencies responsible for
maintaining the areas between the valley walls of the
river…clearing brush in areas prone to flashfloods, checking
for pollution, etc.
Drainage Patterns:
1. Dendritic drainage patterns are the most common type of
drainage basin. The collection of tributaries leading to the main
stream resemble (as viewed from the air) as the veins of a leaf. A
tributary forms a “V” where it joins the main stream. Dendritic
Patterns occur in regions where the underlying bedrock is
relatively uniform.
2. Trellis drainage patterns form a series of fairly straight, parallel
streams intersected at right angles by short tributaries due to
resistant and non-resistant bedrock. This pattern can also
develop in areas that have undergone series of faults or joints.
3. Radial drainage patterns develop where a number of streams
on a mountain radiate outward from the peak.
Groundwater
Groundwater or Phreatic Water – water found in the saturation zones
of subsurface strata.
Aquifer – is a body or rock layer that is porous and permeable enough
to yield economically sufficient quantities of water.
A. Porosity and Permeability
1. Porosity is the portion of the volume of a material that
contains open spaces.
2. Permeability is a measure of the speed at which fluid can
travel through a material. Permeability of unfractured rock and
soil is largely dependent upon particle size, porosity, size of
pores, and amount of interconnections between the pores.
3. Uncemented sediment such as sand and gravel are both
porous and permeable.
4. Cementation occurs when water carrying dissolved ions
(SiO2, CaCO3, Fe2O3, etc.) deposits those ions as chemical
precipitates within the pore spaces. The rock is still porous,
but permeability is greatly lowered.
B. The Water Table
1. Groundwater is pulled downward by gravity.
2. Electrical forces can also pull water upward through small
channels in a process called capillary action.
3. Water does not descend into the crust indefinitely; it
accumulates above an impermeable barrier such as clay.
4. Zone of Saturation – is the completely wet layer of soil and
bedrock above the impermeable barrier.
5. Water Table – is the top of the zone of saturation.
6. Zone of Aeration or Unsaturated zone – the soil and rock
materials above the water table.
7. Capillary Fringe – is the boundary between the zone of
saturation and the unsaturated zone. This is where water
rises upward due to capillary action.
8. Soil-Moisture Belt – is the uppermost layer of soil that usually
contains moisture.
9. Well – a hole dug or drilled into the zone of saturation.
10. Aquifer - is a body or rock layer that is porous and
permeable enough to yield economically sufficient quantities of
water.
11.Recharge Zone – the portion of the aquifer layer that outcrops
at the surface and receives meteoric water (rainfall) to
“recharge” or refill the aquifer. If the recharge zone is
destroyed or covered over, the aquifer may be lost as a useful
water supply.
C. The Movement of Groundwater
1. Nearly all groundwater flows slowly.
2. The rate will depend upon the permeability of the rock and the
nature of fractures and joints in the bedrock.
3. In general, the water table follows the contours of the land and
rises and falls with the topography.
4. In a moist climate, the water table lies above the stream and
water seeps from the ground into the stream. This is a
gaining stream or effluent stream.
5. Groundwater flows from the areas of highest pressure toward
the zone of lowest pressure
6. In dryer climates, a stream that loses water to groundwater is
called a losing stream or influent stream.
D. Springs
1. Spring – a place where groundwater flows or seeps from the
ground to form a small stream or pool.
2. Perched Water Table – In some places a band of
impermeable rock may lie above the main water table creating
a local saturated zone. Perched water tables may intersect
the surface and form springs.
3. Faults, Fractures in Bedrock, and Caverns – may form
springs.
E. Artesian Wells
1. Artesian Aquifer – An inclined aquifer bounded on the top
and bottom by impermeable rock layers. This allows for the
buildup of pressure in the layer.
2. Artesian Well – a well drilled into an artesian aquifer where
water will rise without pumping.
F. Uses and Misuses of Groundwater
1. Public Water Supplies - In many places groundwater is
abundant. It is stored in the earth and remains available
during dry periods.
2. Irrigation – of many farms and ranches is dependent upon
groundwater.
3. In some areas, groundwater from humid areas flows
subsurface into arid regions making water available in those
dry areas. This is the source of some desert oasis.
4. Cone of Depression – Each well pumping water from the
water table causes a localized drop in the water in a circular
conical depression around the well. If wells are drilled too
close to others, the cones of depression overlap and can
cause some of the wells to run dry.
5. Depletion of Groundwater – example: The Ogalala Aquifer is
a layer of porous sandstone and conglomerate extending from
eastern Colorado into Kansas, south into northern New Mexico
and Texas, and Western Oklahoma. Because of the crushing
of the recharge zone and early overgrazing from the cattle
industry of the late 1800’s till today, the Ogalala Aquifer is
running out of water. In some areas it is dry.
6. Pollution of Groundwater – example: The state of Ohio used
injection wells in the 1950’s and 1960’s to get rid of some
industrial wastes. These seeped through the aquifers making
many unusable. Attempts were made to clean the aquifers
with other chemicals, but it will take time for the chemicals to
break down.
7. Subsidence – This is the sinking of the ground due to the
removal of subsurface water. In an aquifer, the water
comprises part of the volume of the layer. Sometimes when
the water is removed, the aquifer layer becomes compressed
resulting in the surface layers dropping. This is common in the
Gulf Coast area of Houston.
8. Saltwater Intrusion – Many times, freshwater lies on top of
saltwater in an aquifer because it is less dense than saltwater.
If too much freshwater is pumped out, some wells begin to
draw saltwater. This is common whenever an aquifer is near
the sea (i.e. Galveston or Beaumont, Texas).
G. Groundwater Pollution
1. Point-Source Pollution – arises from a specific point such
as a certain septic tank, a landfill, or a particular factory.
These are traceable to a culpable source. The pollutants may
be bacterial, viral, or chemical pollutants. In Ohio, the injection
wells used in the 50’s and 60’s are a good example.
2. Non-Point-Source Pollution – arises in a larger area and the
source cannot be readily identified since there may be many
contributors to the problem. Examples include agricultural
runoff polluting a large area of farming districts of Southern
California, Texas, Florida, etc. These may be fertilizers,
pesticides, herbicides, etc.
3. Cleaning Aquifers – has been attempted by using engineered
bacterial agents pumped into wells that biologically breakdown
toxins. Some of these bacterial agents are naturally occurring
but need time for results to be seen.
4. Prevention of Groundwater Pollution – is the best step to
take. Laws in Texas to help prevent groundwater pollution
have been passed. These include making it illegal to dump
used motor oil on the ground. One quart of motor oil has the
possibility of pollution 250,000 gallons of water. A typical car
engine uses 4-5 quarts…therefore the oil contained within has
the potential of polluting over 1 million gallons of water!
Geothermal Energy
A. Geothermal Energy –
1. Refers to hot water or steam produced naturally used to
generate electricity or used directly to heat homes or other
buildings.
2. The U.S. is the largest producer of geothermal electricity, but
geothermal energy contributes only a small fraction of the total
energy consumed.
B. Hot Springs
5. If aquifers are in areas of magmatic activity, the water may
become heated. If this aquifer breaches the surface, hot
springs may be produced.
6. There are very many areas in the world where hot springs are
found…Hot Springs, Arkansas and Yellowstone National Park
are two of the most famous areas.
C. Geysers
1. Geysers – are violent surface eruptions of hot water and
steam.
2. Generally they form in open cracks and channels in hot
underground rock.
3. Water temperature must be at or near boiling (2120 F or
1000C)
4. As water in the cracks in the hot rock heats up, chambers of
air can become compressed. As the temperature rises, the
gas expands forcing the hot water upward to the surface.
After the eruption, the cooled water trickles back into the
cracks, sealing up internal pockets of air in side chambers. As
the temperature rises, it erupts again.
5. Geyser eruption is cyclical and can be timed with a watch.
Each geyser is different, but the cycle of eruption-refill-heatingeruption is fairly repetitive (i.e. Hence “Old Faithful” got its
name for this cyclical nature.).
Karst Topography
A. Karst Topography –
1.
Karst topography - refers to an area where landforms
are created from dissolved rock, typically limestone or
other carbonate rocks.
2.
Features include caverns with various speleothems,
sinkholes, or numerous circular lakes or holes in the
surface.
B. Caverns
7. Caverns or caves form whenever groundwater percolates
through cracks in limestone, dissolving the rock and enlarging
the cracks over time (many times involving millions of years).
8. Most caverns or caves form at or below the water table.
9. Some caverns are small, but others such as Carlsbad Caverns
New Mexico or Mammoth Cave Kentucky are extensive
systems the go on for miles.
C. Speleothems
6. Speleothems – are all depositional features formed in caves
by the action of water. Speleothems are typically composed of
calcite (CaCO3), but can be other soluble materials as well.
7. Stalactites – are icicle-like dripstone features that hang from
the ceiling of a cavern.
8. Stalagmites – build up from the floor as drips of mineral-laden
water deposits its dissolved ions.
9. Columns – form whenever stalactites and stalagmites meet.
10.Speleothems – form at a very slow rate. Some estimates
show that a cubic centimeter of material (a sugar cube in size)
may take 100 years to deposit.
D. Sinkholes
12.If the roof of a cavern collapses, a depression called a
sinkhole forms at the surface.
13.If the sinkholes fill up with water, they form circular lakes.
14.Sinkholes may form slowly as the roof of the cavern dissolves
away, or rapidly as the roof of the cavern suddenly collapses.
15.Sinkhole activity may be intensified by human activity
such as building road-cuts or blasting for seismic surveys.
GLACIATION
GLACIERS OF THE WORLD
A. Alpine Glaciers
1. Glaciers that form in mountainous terrain
2. Exist on every continent
3. Their formation depends on both temperature and
precipitation.
B. Continental Glaciers
1. Also called an ice sheet
2. Glaciers that form a continuous cover of ice over areas of
50,000 km2 or more
3. Spreads out in all directions under its own weight
4. Vast continental glaciers covered much of what are now
North America, Europe, Asia, and parts of the southern
continents at certain times in the past. These periods are
called ice ages.
THE MOVEMENT OF GLACIERS
A. Basal Slip
1. One component of glacial movement
2. The entire mass of the glacier slides along the bedrock and
is accelerated by the presence of water between the ice and
the bedrock.
3. Factors the increase the temperature at the bottom of a
glacier.
a. heat from the interior of the Earth
b. friction from glacial movement
4. Ice can melt at the bottom of the glacier as a result of
increased pressure.
B. Plastic Flow
1. At the surface of a glacier, pressure is low and the ice acts
as a brittle solid.
2. At greater depths the pressure is sufficient to deform ice
crystals in a plastic manner.
3. The plastic portion of the glacier moves by plastic flow in
addition to basal slip. The ice deforms and flows without
fracture.
4. Obstructions to glacial flow do not affect the lower plastic
layer of the glacier but cause the upper brittle zone to
develop fractures or cracks called crevasses.
C. The Mass Balance of a Glacier
1. The buildup of snow, firn, and ice occurs in the accumulation
area.
2. The firn line or snow line is the boundary between
permanent snow and seasonal snow. The firn line varies
with conditions and may shift up and down the glacier from
year to year.
3. In the lower part of a glacier, called the abiation area or
zone of wastage, more snow is lost in the summer than
accumulates in the winter. Glacial ice flows downward form
the accumulation area to the ablation area and continuously
replenishes it.
4. The end, or foot, of a glacier is called the terminus.
a. usually located on land
b. Tidewater glaciers extend directly into the sea
dropping off abruptly into the sea.
 The terminus is often a steep ice cliff dropping off
abruptly into the sea.
 Giant chunks of ice break off, or calve, forming
icebergs.
5. Glaciers grow and shrink
a. the lag time between a change in climate and the
advance of a glacier
 may range from a few years to several decades
 depends upon the size of the glacier, its rate of
motion, and the magnitude of the climate change
b. If the average annual snowfall decreases or the
average yearly temperature rises, the accumulation is
shrinks both in size and thickness and the glacier
retreats.
GLACIAL EROSION
A. Processes of Glacial Erosion
1. Glaciers scour huge areas of bedrock and erode
landscapes
a. Meltwater seeps into cracks in bedrock at the base
of a glacier and then refreezes, prying loose particles or
rock in a process called plucking.
b. As a glacier flows over the loosened particles, it
lifts them into the flowing ice and carries them down slope.
2. Once rocks and the fine sediment are incorporated into a
glacier, the entire mass continues to slide over bedrock.
a. These particles embedded in the base of the glacier
mark the bedrock by deep, parallel grooves and
scratches called glacial striations.
b. If sediment near the base of a glacier is very fine, the
bedrock is not gouged or scratched, but is instead
polished to a smooth shiny finish creating glacial
polish.
c. The process of abrasion grinds rocks into silt-sized
sediment called rock flour.
B. Erosional Landforms Created by Alpine Glaciers.
1. A cirque is a horseshoe-shaped depression gouged out of
the mountainside.
a. A cirque is formed by the glacier movement and
plucking rock leaving a depression’
b. Mechanical weathering by frost wedging and mass
wasting increase the size of the depression
2. Glaciers that form on opposite sides of a mountain ridge
will result in a sharp, narrow ridge, called an arête.
3. If three or more cirques form on different sides of a peak
carving small glacial valleys, separated by arêtes, that lie high above
the floor of the main valley, a hanging valley is formed.
a. Hanging valleys form when these are tributary
glaciers that do not scour the valley as deeply as the
large central glacier.
b. If the larger central glacier cuts off the lower portion
of an arête, a triangular-shaped rock face called a
truncated spur forms.
5. U-shaped valleys form due to deepening and widening
effects of the glacier.
6. A small lake, or tarn, forms at the base of the cirque if
the glacier melts.
7. Paternoster lakes form as glaciers pluck out a sequence of
small
basins in a glacial valley. Lakes will occur in a series
connected by
fast-flowing streams, rapids, and waterfalls.
C. Erosional Landforms Created by Continental Glaciers
1. Continental Glaciers erode the landscape in much the
same way as mountain glaciers do
2. If a glacier covers a knob of bedrock, the rock will be
sculpted to form an elongate, streamlined hill called a roche
moutonnee
a. The upstream side is typically gently inclined,
rounded, and striated by abrasion
b. Formed both by alpine and continental glaciers.
LANDFORMS CREATED BY GLACIAL
DEPOSITION
A. Landforms composed of till
1. Drift is all rock or sediment transported and deposited
by a glacier
and is subdivided into two categories
a. Till is deposited directly by glacial ice and is not
transported and deposited by a stream
b. Stratified drift consists of sediment that was transported
by a glacier and then reworked and deposited by water
2. Erratics are boulders transported by glaciers that are
different than those found in the vicinity
3. Moraines form when till a glacier deposits till
a. Types of moraines
 Terminal moraines are found at the end of the
glacier before the glacier begins to retreat
 Ground moraines are relatively tin layers of till
spread over a broad area
 Recessional moraines are new mounds that form
when a glacier stabilizes during its retreat, and the
terminus remains in the same place for a year or
more.
b. End moraines and ground moraines are
characteristic of both alpine and continental glaciers.
c. The extent of continental glaciers of the Pleistocene
Epoch can be determined by locating the end moraines
d. Alpine glaciers also deposit lateral moraines along the
sides of the ice
e. Tributary glaciers that both have lateral moraines can
combine placing the moraines in the center of the
glacier forming medial moraines.
4. Drumlins are elongate ills composed of stratified till
or drift
a. Some were probably deposited beneath a glacier
b. Others may be remains of old moraines
c. Formed when a glacier flows over and reshapes a
mound of sediment
d. The stream-lined shape is elongated in the same
direction as the glacial flow
C. Landforms composed of Stratified Drift
1. Outwash is material that has been eroded by the glacier and
is transported and deposited downstream
2. Valley train is the outwash deposited in a mountain valley
by the streams flowing from an alpine glacier
3. Outwash plains form when sediment spreads out from the
confines of the valley into a larger valley or plain. Is
characteristic of continental glaciers.
4. Kames are small stream-deposited mounds that form when
sediment collects in a crevasse or other depression in the
ice or at the margin of a glacier
5. Eskers are long, snake-like ridges that form as the bed
deposit of a stream that flowed on, within, or beneath the
stagnant glacial ice.
6. Kames and eskers can be distinguished from till
because they are sorted.
7. Kettles are formed from large blocks of ice that were left
behind as the glacier receded that were surrounded by
sediment eventually forming g depressions.
8. Lakes commonly form adjacent to glaciers because ice and
moraines dam normal drainage patterns
a. Sediment in the lakes is often layered into coarse and
fine-grained, organic-rich layers.
b. Layering due to seasons
c. One set of layers is called a varve marking one year’s
time.
THE ICE AGES
A. Introduction
1. An ice age or glacial epoch is the time of extensive
glacial activity,
when alpine glacier descent into lowland valleys and
continental
glaciers spread over the higher latitude.
2. It is relatively easy to trace the extent of the most recent
ice age
because landforms and other features created by the ice
are well
preserved.
a. glacial evidence – when glacial till is lithified, it forms a
sedimentary rock called tillite, a conglomerate of unsorted
glacial sediment
b. Geologic evidence shows that at least 8 major ice ages
have occurred
 Pleistocene Ice Age: the most recent ice age that
occurred mainly during the Pleistocene Epoch
 During the most recent advance, glaciers reached
their maximum extent about 18,000 years ago.
B. Effects of Pleistocene Continental Glaciers
1. Terminal moraines lie south of the Great Lakes, and
extend
westward into Montana, and eastward into southern New
York.
2. The Great Lakes were also scoured and deepened by the
continental ice
3. The outwash plains form the fertile farmland of the
“breadbasket” of
North America.
4. Pluvial lakes formed in the Southwest
5. depression of the land
6. lowered sea level
7. Fjords are deep, marrow lakes that extend far into the
land
C. Causes of Ice Ages
1. Major glacial epochs and plate tectonics
a. Ice ages occur when the continents are positioned close to
the polar regions
b. Can be used to explain climate changes over periods of
tens or hundreds of millions of years
2. The cycles of Pleistocene Ice Age and orbital variations
a. explain the shorter cycles of glacial advances and retreats
b. variations in the earth’s orbit
 The shape of the Earth’s orbit around the sun
changes on about a 100,000 year cycle and is
known as eccentricity
 The tilt of the Earth’s axis changes on a 41,000
year cycle
 Precession, or the circling of the Earth’s axis,
completes a full cycle every 23,000 years.
c. Orbital changes affect the distribution of sunlight with
respect to latitude and season
d. Milutin Milankovitch plotted the cycles of the three
different orbital variations
 calculated the combined effects of all three
variations on the Earth’s climate
 showed that the three regular, periodic orbital
variations should combine to generate alternating
cool and warm period in the higher latitudes
e. Climate studies or marine organisms make it possible to
graph variations in global temperature over he past several hundred
thousand years. This data aggress with Milankovitch
calculations.
Deserts of the World
A. Deserts Defined
1. defined primarily by the amount of precipitation: generally
less than 25cm or 10in per year, or areas that have more
evaporation than precipitation.
2. This supports only sparse vegetation hence desert soils have
a very thin or absent humus layer or “O” layer.
3. Animals (including humans) and plants living in deserts have
adapted to the dry conditions of deserts.
B. Effects of Latitude
1. About 25% of the earth’s surface outside the polar regions is
desert.
2. Technically, Antarctica is a desert because it has more
evaporation than precipitation.
3. Most arid regions lie between latitudes 200 and 300 north and
south of the equator.
a. The sun shines most directly at or near the equator
warming the air near the surface
b. The warm, moist air rises, forming a region of low
pressure
c. As it rises it cools and the water vapor condenses, falling
out as rain in the tropical rainforest near the equator
d. The now dry air falls back toward the earth at about 300
north and south of the equator creating a zone of high
pressure
e. High pressure heats the air and enables it to hold more
water vapor, evaporating water from the surface forming
the desert region
C. Effects of Topography: “Rainshadow” Deserts
1. A rain shadow desert forms on the leeward (downwind) side
of a mountain
a. moisture-laden air masses flowing over a mountain lose
their moisture on the windward side (i.e. Seattle, WA.)
2. Deserts formed due to climate and geography of the
continent. In some regions, deserts extend to the seashore,
while in other regions the interiors of continents are humid.
The climate at any particular place on the earth results from a
combination of many factors:
a. Latitude
b. Proximity to the ocean
c. Direction of the prevailing winds
d. Direction and temperature of ocean currents
e. The position of mountain ranges
D1. Water in Deserts – Desert Streams
1. Desert streams – In some deserts, large rivers flow through
as in Northern Egypt. This allows for agriculture along the
narrow flood plains of the river.
2. A “wash” is the term for a desert streambed that is dry for
most of the year. It may have all of the characteristics of a
stream, but without the water.
3. Flash floods are common in desert regions. Typically deserts
receive around 10 inches of precipitation per year, but many
times it all comes within a 1 to 2 day period. The washes
during the dry times may become clogged with debris that
form temporary dams during rains. When the dams break, a
flash flood rushes downstream. When the downpour is
unusually heavy the saturated desert soil itself may begin
to flow!
4. Debris flows are viscous fluids composed of mud and water
that flows down slope, carrying boulders, trees, logs, or
anything in its path.
5. When floods pour out of the mountains onto the valley, the
water slows abruptly and most of the sediment is deposited at
the base of the mountain in a fan-shaped structure called an
alluvial fan.
D2. Water in the Desert (cont.) - Desert
Pediments and Bajadas
1. A bajada is a broad depositional surface formed by the
merging of many alluvial fans. These may extend from the
mountain front out into the inland basin for 10’s of kilometers
2. As the mountain front continues to erode and retreat, a gently
sloping erosional bedrock surface called a pediment
develops. The pediment forms uphill from the bajada.
3. It is difficult to distinguish between a pediment and a bajada
because of the thin veneer of sand and gravel on a pediment.
4. Together, a bajada and a pediment form a single surface that
becomes gently steeper as it approaches the mountain front
called the piedmont slope.
D3. Water in the Desert (cont.) – Playa
Lakes
1. A playa lake is an intermittent desert lake that only exists after
sufficient rainfall. The runoff from flashfloods or streams
accumulated temporarily in the middle of the desert valley. It
may cover a large area but may only be inches deep. It
quickly is absorbed by the soil or evaporates leaving behind its
dissolved salts (salinization of deserts)
2. These salts accumulate over time forming evaporite layers of
halite, sylvite, gypsum, etc.
3. The abundance of salts prohibits a lot of vegetation growth
thereby not allowing the development of an “O” horizon in the
soil.
4. “Caliche” or “hard-pan” is the term for the hard beds of salts
found in desert soils.
5. The term “playa” also applies to the shallow, almost flat,
central part of a desert basin in which water gathers after a
rain. This is comprised of very fine sands, silts, and clays,
along with the associated evaporite salts.
E. Wind in the Desert
1. Deflation is the general term for erosion by the actions of
wind. Usually wind only moves small particles such as silt and
sand.
2. Desert pavement forms whenever deflation occurs taking
away the smaller particles and leaving the larger particles
behind.
3. Wind-blown sand particles are commonly carried by saltation
whereby the grains bounce along the ground.
4. If the wind repeatedly scours a particular area, small
depressions called blowouts are formed. Ultimately, the
lower limit for a blowout in the water table.
5. Abrasion occurs whenever the sand and silt laden wind
currents blast against other rocks. The strongest forces of
wind abrasion occur at a height of less than 1 meter.
6. Ventifacts are cobbles or boulders lying on the surface that
have developed flattened and worn surfaces over time. The
gentle slope points in the direction of the prevailing wind, and
the steeper slope indicates downwind. Many times ventifacts
have two or three sides polished due to changing wind
direction.
G. Dunes
1. Dunes are a mound or ridge of wind-deposited sand common
in deserts and sandy coastlines.
2. Dunes are asymmetrical in cross-section as sand from the
windward side of the dune is eroded, and then it is
deposited on the leeward side. This lee side of the dune is
called the slip-face.
3. Dunes can migrate over time and can sometimes inundate
highways and buildings. Attempts by people to halt the
advancement of dunes include planting vegetation, building
artificial windbreaks, or even covering the dune with tarry
petroleum products.
4. “Fossil” dunes form whenever dunes are buried by other
sediments and eventually lithified, preserving their aeolian
cross-bedded structure and ripple marks. Cross-bedding
is the preserved layers of the slip-face of a dune.
5. Types of sand dunes:
a. Barchan dunes – are crescent-shaped with the tips of
the crescents pointing downwind. These migrate across
the landscape independently and form in areas where little
sand is present.
b. Transverse dunes – form perpendicular to the wind
direction in areas where sand is plentiful, the whole dune
moves at the same speed and the dunes migrate in long,
parallel ridges.
c. Parabolic dunes – If vegetation is more plentiful, dune
shapes are determined by the orientation and abundance
of the plants. If a local disturbance destroys the
vegetation in an area, a blowout can form by local
deflation. This creates parabolic dunes that are common
in moist, semi-desert regions and along seacoasts.
d. Longitudinal dunes – If the wind direction is erratic but
prevails from the same general quadrant of the compass,
and the supply of sand is limited, longitudinal dunes
form parallel to the wind direction.
F. Loess
1. Loess is the accumulation of wind-blown silt. This is
extremely porous, strikingly uniform, and typically lacks
layering. Loess often forms vertical cliffs and bluffs.
2. The largest deposits of loess are found in central China,
although it is also abundant in the Middle-East, as well as the
U.S.
3. Silt formed in abundance during the Ice Ages of the
Pleistocene. As this silt was moved by the winds after the
regression of the glaciers, it was deposited ultimately forming
soils that are generally fertile and possessing a high porosity.
G. Desertification
This can be defined as the expansion of deserts due to:
 Changes in climate
 Loss of irrigation processes (natural or man-made)
 Removal of natural vegetation…changing weather patterns,
over grazing of animals, excessive clear-cutting in some
areas, etc., or the continuance of bad agricultural practices.
H. Two Desert Landscapes in the U.S.
The Colorado Plateau and the Sonoran Desert
1. The Colorado Plateau – The Four Corners area was once
covered by shallow seas, lake beds, and deserts. As
sediments accumulated, rocks formed and the land was
uplifted forming a plateau.
2. A plateau is a large elevated area of comparatively flat land.
3. Steep-sided flat-topped mountains called mesas and buttes
form prominent features throughout the Four Corners area.
4. A mesa is a flat-topped mountain shaped like a table that is
smaller than a plateau.
5. A butte is also a flat-topped mountain, but it is characterized
by very steep sides, and is more tower-like than a mesa.
Generally speaking, mesas are wider than they are tall, and
buttes are taller than they are wide.
6. Erosion is from rivers and streams, and lateral erosion along
joints.
7. Due to low rainfall amounts, the vertical cliffs are not rounded
rapidly. Today’s broad mesas, narrow buttes, and sharp,
angular towers characterize the Colorado Plateau.
-------------------------------------------------------------------------------------------1. The Sonoran Desert is a region of parallel granetic mountain
ranges separated by extensive basins known as the Basin
and Range Province.
2. It consists of gently sloping bajadas and pediments, with
steeper alluvial fans along the mountain fronts.
3. Playa lakes occupy some of the basin interiors.
4. The Sonoran Desert has no through-flowing drainage system.
OCEANS and COASTS
OCEAN WAVES
A. Characteristics of Ocean Waves
1. Factors that determine the size of a wave
a. the wind speed
b. the length of time that the wind has blown
c. fetch: the distance that the wind has traveled
2. parts of the wave
a. crest: the highest part of a wave
b. trough:
c. wavelength: the distance between successive crests
d. wave height: the vertical distance from the crest to
the trough
3. the movement of water
a. The water doesn’t travel at the same speed or in the
same direction as the wave itself
b. The water moves in circular paths
c. The movement of water in an ocean wave is deeper
than the trough of the wave and continues downward
in decreasing circles.
The disturbance occurs ½ the depth of the wavelength
d. As the wave approaches shore it begins to :feel
bottom: and become steeper.
 The frictional drag between the wave base and
sea bottom slows the entire wave
 At the same time their crests become higher until it
can no longer support itself and collapses forward
or breaks
 Once the wave breaks the water in the wave flows
toward the beach as a chaotic, turbulent mass
called surf.
B. Refraction
1. Most waves do not strike the shore directly, but rather meet
it at an angle in a process called refraction.
C. Storm surges: The Giant Wave
1. Factors that contribute to the maximum height of a wave
a. storm surge: during a large storm, an onshore wind
pushes the surface of the ocean against the shore
with enough force to raise sea level.
b. During high tide
c. Configuration of the ocean bottom
D. Wave Erosion
1. most intense during storms
2. types of wave erosion
a. water forced into cracks or crevices in the rock
compressing the air within the cracks
b. sediment is driven against the shore, bedrock is warn
away by abrasion
OCEAN CURRENTS
A. Mid-Ocean Currents
1. A sea wave is a periodic oscillation of water while a current
is a continuous flow of water in a particular direction.
2. Prevailing winds push the surface water of the ocean to
generate broad, slow, mid-ocean currents
a. These currents are deflected into circular paths by the
rotation of the Earth
b. Ocean current affect climates by carrying warm water
form the equator toward higher latitudes or cold water
from the Arctic and Antarctic toward lower latitudes.
B. Currents Close to Shore
1. Smaller scale currents that flow close to the shore are
generated by waves
Rip current or undertow: the outward flow of the wave as
the water flows back toward the sea (toward deeper water)
2. If waves regularly approach shore at an angle, a longshore
current will flow parallel to the coast.
a. Longshore currents flow in the surf zone and a little
further out to sea
b. Sediment carried by longshore currents is called
longshore drift.
3. Most sediment found on a coast is not produced by erosion
at that location, but rather is carried seaward by streams,
deposited on deltas, and transported and deposited along
the coast by longshore currents.
THE WATER’S EDGE
A. Beaches
1. Any strip of shoreline that is washed by waves and tides
2. beach zones
a. foreshore, or intertidal zone, lies between the high
and low tide lines
 alternately exposed to the air at low tide and
covered by water at high tide
c. backshore is usually dry, but is washed by waves
during storms
 The storms deposit and erode sediment and
dislodge vegetation
 The backshore can be wide or narrow, depending
on the topography and the frequency and intensity
of storms
3. Rocky beaches are characteristic of coastline with a limited
amount of sand and other fine sediment
4. Sandy beaches dominate shorelines where a rich supply of
sand is available.
B. Reefs
4. A wave-resistant ridge or mound built by corals or other
marine organisms
a. need sunlight and warm, clear water to thrive
b. Only the outer and topmost portions of a reef contain
living organisms
5. The largest reef in the world is the Great barrier Reef
6. If a circular reef builds around a volcanic island, the reef may
rise as the island subsides
 Once the island disappears beneath the ocean,
the circular reef called an atoll encloses a lagoon
with no land inside the circle.
SEDIMENT-RICH COASTLINE
A. Sources of Sediment
1. Some beach sediment forms by erosion of bedrock along
the coast
itself.
2. Major rivers carry large quantities of sand, silt, and clay to
the sea and deposit it in deltas
3. Additional sediment is derived from glacial till that was
deposited during the Pleistocene Ice Age.
4. Sediment from all sources is distributed by longshore
currents
B. Emergent Coastlines
1. Land that was previously submerged is exposed and the
new shoreline moves outward toward the ocean.
2. If a coastline emerges intermittently over a period of time,
several levels of old shorelines called beach terraces are
exposed.
3. Large quantities of sediment from the land wash into the sea
and
are deposited on the continental shelf
4. Formation of emergent coastlines
i. Land can rise as a result of isostatic adjustment
ii. Slowing down of sea-floor spreading
iii. Local or regional tectonic uplift
C. Characteristics of Sediment-Rich Coastlines
1. A spit is a long ridge of sand or gravel extending out from
a beach
2.When a spit blocks the entrance to a bay, it is called a
baymouth
bar.
3. If an island lines close to a sediment-rich beach, a bar or
spit-like structure called a tomobolo may form connecting
the island to the mainland.
Often forms as waves refract from an island and strike the
nearby beach at an angle.
4. A barrier island is a long, narrow, low-lying island that
extends parallel to the shoreline
5. Formation of barrier island
a. shallow coasts where waves lose energy away from
shore accumulate
b. deposition by longshore currents
c. sea level changes
SEDIMENT-POOR COASTLINES
A. SUBMERGENT COASTLINES
1. develops when the land sinks or sea level rises causing
the shoreline to move inland
a. Bedrock is exposed or covered by only a thin
layer or regolith
b. Commonly irregular with many bays and headlands
because they form when stream valleys, hills and other
topographic features are flooded.
c. Small beaches form in protected coves, but cliffs border
much of the coastline.
2. Erosion gradually straightens such an irregular coast
a. Wave-cut cliffs form when the lower parts of rock
faces are eroded by waves
b. As the cliff retreats, a flat or gently sloping wave-cut
platform is left behind.
c. If waves cut a cave into a narrow headland, the cave
may eventually erode all the way through the headland
forming a sea arch.
d. A sea stack forms when an arch collapses.
FJORDS AND ESTUARIES
A. Fjords: long, narrow, steep-sided canyons cut into mountainous
coastlines
1. Characteristic of submergent coastlines
2. Glacially scoured coastal valleys that were flooded by rising sea
level.
B. Estuary
1. A bay formed when rising sea level or a sinking coast submerges
a broad river valley. They are shallow and have low-profile
beaches.
2. Chesapeake Bay is a major estuary along the Atlantic Coast of
north America that was formed by submergence of a major river
valley
3. Estuaries are extremely rich marine environment. Streams wash
nutrients into them, and the shallow water provides habits for a
variety of marine organisms.
CASE HISTORY 1: THE SOUTH COAST OF LONG ISLAND
A. A natural System in Equilibrium
1. Long Island is a narrow, low-lying island extending eastward
from New
York City and separated from Connecticut by Long Island
Sound.
a. The northern edge and eastern tip of the island consists of a
series of glacial moraines.
b. A series of narrow, low-lying barrier islands lies along the
southern coast.
c. Longshore currents flow westward
d. The beach, in equilibrium, remains stable.
2. The beaches change seasonally and during storms.
a. In winter the beaches erode and become narrower.
b. In summer waves carry sand back shoreward and rebuild
the beaches.
c. Hurricanes shrike periodically generating storm waves that
completely overrun the barrier islands and roll inland,
flattening dunes and eroding beaches.
3. Over longer periods of geologic time, the barrier islands and the
beaches are transient landforms.
B. Human Intervention
The natural fluctuations of a beach are not always compatible with
human activity.
1. Many beach property owners try to protect their beach by
building a large
Barrier called a groin. Groins trap sand and prevent the
beach from
Receding in the winter but interrupts the flow of sand.
2. Sea walls interrupt the gradual adsorption of wave energy by a
beach and cause more erosion.
CASE HISTORY 2: THE MISSISSIPPI
DELTA
A. Natural processes the reduce the amount of land on a delta
1. Sea level change
2. Subsidence
3. Erosion
B. Causes Reducing the Growth of the Delta
1. Decreased sedimentation; flood control projects
2. Increased subsidence; extraction of subsurface liquid
3. Increased erosion
a. removal of the natural vegetation
b. building of sea walls
c. development of artificial canals
GLOBAL WARMING AND SEA LEVEL
RISE
A. Melting of Glaciers
If global temperature warmed slightly, the sea ice fringe could melt
and its resistance to the movement of the glaciers would be removed.
Large amounts of interior ice would then flow more rapidly into the sea
where it would melt.
B. Change in Volume of Seawater with Temperature
Expansions of water would cause a rise in sea level
C. Future Concerns
1. Sea level has been rising over the past century.
2. Coastal farmland and villages will be flooded in many
countries if the trend continues.
Economic Resources
Categories of Resources:



Fuels: petroleum, coal, natural gas, and uranium
Metals: iron, copper, aluminum, silver, gold, zinc, etc.
Nonmetals: sand, gravel, limestone, granite, marble,
phosphorus, potassium, sulfur, etc.
Fuels:
I. "Fossil Fuels"
"FOSSIL FUELS" are formed by the alteration of buried organic
remains over long periods of time. They are considered NONRENEWABLE because of the vast amount of time necessary for the
transformation of organic remains into petroleum or coal: consumption
outpaces formation. Living organisms utilize energy in the form of
foodstuffs taken into their bodies while alive. Most energy available for
life on earth starts with the sun. Solar energy is trapped and converted
into chemical energy by green plants in the processes of
photosynthesis. During this process, CO2 and H2O are converted into
sugars. These sugars enter the food chain of life. For instance, plant
sugars are eaten by other organisms for energy to power their bodies
(i.e. cows eating grass). People eat cows for nutrition and an energy
supply, thereby humans power their bodies by utilizing sunlight energy
indirectly.
When life forms die, there is considerable energy present in the
form of chemical bonds that made up the organism's body. On land,
this dead material is usually consumed by scavengers, fungi, and
bacteria. If the dead organism's body is quickly buried, that energy in
the organic remains can be converted into other chemical compounds
by the heat and pressure associated with burial. Many of these
compounds such as coal or petroleum can be extracted from the
ground and burned, releasing the stored chemical energy. In essence,
whenever you drive your car, the burning gasoline is releasing sunlight
energy that was trapped as chemical energy by life forms millions of
years ago.
A. Coal
 Coal forms in low energy, reducing, swampy areas
where dead vegetative matter accumulates on the
bottom. Over time, more vegetation piles up, and as
the pressure increases, the vegetative matter is
converted into what we call "coal". There are various
stages of coal each dependent upon the degree of
pressure:
1. Peat
2. Lignite
3. Bituminous
4. Anthracite (a metamorphic form of
coal)
 Mining coal can be a dangerous business because of
the inherent hazards of working in mines, along with the
danger of the buildup of toxic gasses released from the
coal as it breaks. Methane is an organic byproduct of
the coal forming process. It is not only very flammable,
but it can build up to the point where miners can
suffocate if ventilation is not adequate.
 Types of mines include open pit and shaft mines.
Open pit mining involves the removal of the overburden
to expose the layer sought. This is easier to mine but is
very damaging to the surrounding area…leaving an
enormous pit whose soils have been destroyed. Shaft
mines involve digging a tunnel-like mine into the layer
sought and then carrying the coal out. These can fill
with water that can be toxic due to the exposure of
chemicals in the rocks. Also, abandoned mines can
pose a danger to the unwary hiker.
 Burning coal can release harmful compounds into the
atmosphere such as sulfide compounds. These
contribute to the acidification of rain causing
deforestation and other ecological damage.
 Large reserves of coal exist in many parts of the world.
Estimates of the future availability of coal show that at
current rates of use, known coal supplies should last
until the year 2200, about another 200 years.
Experiments have been performed to try to convert
poor grade coal into petroleum liquid. It can be done,
but with current technology it is economically
unfeasible.
B. Petroleum
 In the seas, there is and has been throughout much of
geologic time considerable amounts of microscopic
"Plankton" floating on the seas. Plankton is comprised
of tiny larvae of other sea creatures, microscopic plants
and animals, and many other small forms of life. Their
numbers are in the trillions. As they die, their dead
bodies "rain" down on the seafloor, becoming
incorporated into the clays, sands, and other
sediments. Over time, these organic rich sediments
become buried and the pressure builds up.
 As the temperature reaches 50 to 1000 C, the organic
compounds are transformed into crude oil. The layer
containing the petroleum is called the reservoir rock.
It is usually porous and permeable enough to allow the
petroleum to migrate. Just like an oil and vinegar salad
dressing separates to where the oil is on top because of
density differences to the vinegar, crude oil separates
from the water associated in the reservoir rock.
Petroleum tends to move up slope.
 As the seafloor may be warped and distorted from
tectonic activity, petroleum moves to the tops of
anticlines and domes. An oil trap may be formed by
faults, salt dome intrusions, or other obstructions of the
petroleum's upward migration in the strata. These
features are searched for by the petroleum geologist
using subsurface seismic studies, core samples, or
other techniques.
 The source rock (reservoir rock) is an oil-rich layer
that has properties of permeability and porosity to allow
oil to be pumped from it.
 Oil Reserve - This is a region of known supplies of
petroleum in the ground, but has not been drilled and
removed yet.
 Migration is the term for the upslope movement of the
oil in the reservoir rock.
 Estimates for future oil reservoirs vary greatly from 30
years at today’s consumption to 150 years at today’s
consumption.
 Secondary Extraction is sometimes used to “wash”
older wells with solvents or detergents to remove any
oil residue that was missed before.
 Oil Shales contain oil organics and are said to be
kerogen-rich. These are sometimes processed to
extract oil.
 Petroleum products vary greatly from fuels and
plastics to fertilizers and medical needs.
C. Natural Gas
 If crude oil is heated to past 1000 to 1500 C, it converts
into Natural Gas.
 Natural gas accumulates upslope in strata. As
pressure builds, “blow-outs” at oil rigs can occur.
 It is estimated that at today’s rate of consumption, we
may have 50 – 200 years of natural gas left.
 Natural gas is used in heating homes, cooking, and is
used in that formation of many petroleum products.
D. Nuclear Fuels
 Usually, only uranium is mined for use in reactors.
 “Nuclear Fission” is the splitting of atoms to release
energy. The energy released is then used to convert
water to steam to drive electric turbines.
 Less than 10% of the energy used in the US is from
nuclear reactors.
 It is a Clean Energy Source but produces radioactive
wastes in the form of spent uranium rods (the rods are
not radioactive enough to use in reactors, but are still
dangerous to life forms.)
 If Nuclear Fusion” is ever perfected (the fusion of 4
hydrogen atoms to form 2 helium atoms), there could
be limitless amounts of “free” energy with no
radioactive waste! This may happen in our lifetime.
Mineral Resources:
 Mineral Deposit – This is a local enrichment of one or more
minerals in an area.
 Mineral Ore – This is a natural material that contains
sufficient mineral materials to be economically feasible to
mine.
 Mineral Reserve – This is a region of known supplies of
ores in the ground, but have not been mined yet.
Processes of Ore Formation:
 Magmatic Processes – Solidifying magma (plutons,
especially super slow cooling sialic masses) can contain
valuable ores.
 Hydrothermal Enrichment – This occurs in the overburden
around magma intrusions whereby mineral laden hot water
fills the cracks with ores. This is responsible for the
“veining” of many ores (i.e. quartz veins that contain gold).
 Sedimentary Processes – Mineral enrichment can occur by
sedimentary processes such as leeching from groundwater,
evaporation and concentration of ions, or by supersaturated
solutions precipitating ores.
 Weathering Processes – The altering of a useless mineral
into a valuable one can occur due to certain surface
processes of weathering such as orthoclase weathering into
kaolinite. Also, the movement of groundwater can
chemically alter some minerals into ores.
Nonmetallic Resources:
These are substances that are contain no high amounts of
metals or chemicals but are still valuable in other ways.
Examples include:
 sulfur for acids, explosives, medicines, etc.
 gypsum for sheetrock, fillers, etc.
 calcite for cements, ceramics, etc.
 Crushed stone and caliche for road materials (Crushed
stone is the largest per capita natural resources used by the
US I the form of road and building use.
 Halite for table salt, stabilizers, etc.
 Other nonmetallic resources include potassium salts, apatite,
boron, etc.
 Most nonmetallic resources are mined or “quarried” in open
pit mines.
Pollution Concerns:
 Mine Tailings – Mining involves moving large amounts of
earth materials to get to the ore. The unwanted materials
are usually piled up near the mine and are called “mine
tailings”. As these tailings are subjected to surface
weathering processes, many harmful pollutants can run off
into rivers and streams. In abandoned mines of the 1800’s,
water has accumulated in many of them creating pools of
acidic or other toxic compounds that may escape into the
environment. Many streams in Colorado that were
considered “pure” water contain high amounts of mercury,
lead, and arsenic.
 Runoff from surface mines may also contributes to pollution
to surrounding water systems and soils.
 Land Restoration is a relatively new major that students
may be interested in pursuing. This involves training in the
biological and geological sciences to clean up and restore
the environment damaged by aspects of mining. This is an
ongoing process by many scientists and mining companies.
 Point-Source – If a pollution problem arises and the source
of pollutants can be traced back to a known source such as
a particular mine or a particular landfill, etc., it is referred to
as Point-Source Pollution…(think of it as that you can
physically point to the source).
 Non Point-Source Pollution – If a pollution problem arises
and the source cannot be traced back to a particular source,
it is referred to as Non Point-Source Pollution. An
example may be a problem with agricultural runoff in a
geographic area such as Southern California, or a harbor
ship channel is polluted but the source is unknown, this is
referred to as Non Point-Source Pollution.