Transcript Mass Movement, Wind, Glaciers

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A down slope movement of loose sediment and weathered rocks
resulting from the force of gravity.
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Erosion following weathering climatic conditions determine which
materials and how much
All mass movements occur on slopes
Several variables influence mass movement
1) Material weight result from gravity
2) Materials resistance to sliding or flowing
3) Trigger ie. Earthquake
4) Water
Movement occurs when a force works and pulls materials is the
stronger than its resistance
Erosion and undermining soil increases the materials pull down of
the slope
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 Too
little H2O does not stop material’s
potential mass movement.
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Increase H2O, weight of material increases
and acts like a lubricant. With the force of
gravity , mudslides.
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H2O moves with material. It is not a
transport agent.
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1. Creeps
2. Flows
3. Slides
4. Slumps
5. Avalanches
6. Rockfalls
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 Creep
- slow/steady flow of loose
weathered material.
 Noticed over a long period of time.
Indication - tilt of structures.
 The slow, downhill movement of loose,
water-logged materials that occurs in regions
of permafrost is called solifluction.
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 Flows
- materials flow as thick liquids.
Speed - few cm’s per year to 100’s km per
hour.
 Swift mixtures of mud and H2O. Trigger earthquakes, volcanic eruptions heat the
earth.
 Common in sloped, semi arid regions - short
rain storms - ex. LA Basin
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 Slides
- Rapid downward movements of
earth materials that
 occur - landslides - speed 200 km per hour.
Stop at the bottom of slope as debris piles.
Common - steep slopes.
 Rockslides - type that occur when a sheet of
mud moves down hill on a sliding surface.
Trigger - Earthquakes.
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A
slump is a mass of material in a landslide that
rotates along a curved surface.
 Locations
of slumps are in areas of thick soil on
moderate to steep slopes and highways.
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Common after rain, reduces friction, forces
between the center of the soil.
Slumps leave crescent shaped scars on the slope.
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 Avalanches
- Landslides that occur in
mountainous areas with thick accumulation
of snow. - slopes 35°.
 10,000 avalanches occur in U.S. Sun melts
the snow.
 It reflects/ more snow added weight causing
breakoff.
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 Rockfalls
- Occur at high elevations in step
road cuts and on rocky shores.
 Physical weathering process - breakdown rock - rock falls straight down.
 Human Factor - affect mass movement
construction - heavy building - roadsweight helps makes slopes unstable.
Leakage/septic tank
seaps around.
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 Catastrophic
mass movement - most
common on slopes greater than 25° with
annual rainfall of over 90 cm.
 Preventative
action for land movement:
trenches along roads to catch debris;
protective fencing; steel netting along
slopes; retaining walls.
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 Wind
transports material up hill and down
erosional agents that are modified, ie. wind
changes the landscapes in arid and coastal
regions.
 Ability
ice.
to move material as less than H2O and
 Wind
transports materials causing them to
move different ways.
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Strong winds - carry long distance (suspension)
Saltation - Bounding motion of particles, ie.
sand wind transport occurs in areas with little
vegetation, ie., desserts, some arid areas,
seashores and lakeshores
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 Wind
transports material up hill and down
erosional agents that are modified, ie. wind
changes the landscapes in arid and coastal
 regions.
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 Ability
ice.
to move material as less than H2O and
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 Wind
transports materials causing them to
move different ways.
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Deflation - lowering of the land’s as
surface result of movement. Problem agriculture regions: 1930’s Dust Bowl Sever dust storms - clouds of dust blown
by the wind create deflation
blowouts - shallow depressions
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 Abrasions
- when particles such as sand rub
against the surface of rocks and other
materials. Rocks shaped by wind blown
sediments are called ventifacts.
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Occurs in arid regions of change in wind
velocity. Particles drop out of the air to
the ground
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Formation of Dunes - sand accumulates
from the dropping of wind. A dune is a pile
of wind blown sand. Conditions necessary
for
formation of dunes:
1) Availability
2) Wind velocity
3) Wind direction
4) Amount of vegetation
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Desert Pavement - when finer sediments are blown
away by wind and the heavier larger particles and
pebbles are left behind.
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Tallest dunes - Sands in Arabia - more than 100m
in height
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Quartzs Sand - most common
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Gypsum Dune - white sand - National Monument in
New Mexico
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Calcite Dune - Bermuda and areas of the Caribbean
Sea
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 Loess
- wind carries fine, lightweight
particles, ie. Clay and silt
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 Loess
deposits - Illinois, Iowa, Missouri,
South Dakota, Nebraska
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 Glacier
– a large moving mass of ice.
 Formed
near the earth’s poles and at high
elevations in the mountains.
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They cover only 10% of the earth.
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 Classified
in two ways:
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1) Valley Glaciers - form in valleys in
high mountainous areas, occurs when
growing ice mass becomes too heavy to
maintain its rigid shape and begins to flow.
 Flow begins when the accumulation of snow
and ice exceeds 20 meters in thickness.
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 2)
Continental Glaciers - cover broad,
continent sized Areas.
 They form under the same climatic
conditions as valley glaciers, but move in a
different way.
 The weigh of this glacier forces it to flatten
is all directions.
 These glaciers are also called ice sheets.
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Of all erosional agents, glaciers are the most
powerful because of their great size, weight,
and density when a valley glacier moves, it
breaks off pieces of rock through a process
called plucking.
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When glaciers with embedded rocks move over
bedrock valley walls, they grind out parallel
scratches into the bedrock.
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Small Scratches are called striations, larger ones
are called grooves.
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Scratches and grooves provide evidence of a glacier’s
history and establish its direction of movements.
Glacier features include:
1) cirques - deep depressions
2) arete - where two cirques on opposite sides of a
valley forming a sharp, steep ridge.
3) horn - glaciers on three or more sides of a
mountain top, a steep, pyramid shaped peak forms. Ex.
Switzerland’s Matterhorn
4) hanging valley - tributary valley that enters a Ushaped valley from high up a mountain side
5) waterfalls
6) U-shaped valleys
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 Glacial
till is the mixed debris that glaciers
carry.
 Moraines
are ridges consisting of till
deposited by glaciers.
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 It
is melt water contains gravel, sand, and
fine silt formed by the grinding action of the
glaciers of the glacier.
 When this sediment is deposited by melt
water, it is called out-wash.
 The area at the leading edge of the glacier,
where the melt water streams flow and
deposit outwash, is called an outwash plain.
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 Glaciers
that move over older moraines and
forms the materials into elongated land
forms called drumlins.
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 Glacial
Lakes - Sometimes a large block of
ice breaks off a glacier and is later covered
by sediment.
 When the ice block melts, it leaves behind a
depression called a kettle hole. After the ice
blocks melts, the kettle hole fills with water
from rain and runoff.
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