MASS MOVEMENTS, WIND, AND
GLACIERS
Chapter 8
Section 8.1 Mass Movements at
Earth’s Surface
Everyday, the landscape surrounding us undergoes
changes. Some are not noticeable, while others have an
extremely visible, immediate effect to the landscape.
What are mass movements?
•The downslope movement of loose sediments and
weathered rock resulting from the force of gravity
•All mass movements occur on slopes
Factors that influence mass movements
* Weight from gravity
* Materials resistance
to sliding
* “Triggers” to start
the movement
* Water
Types of Mass Movement
CREEP
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The slow, steady, downhill
flow of loose, weathered
Earth materials
Usually only seen over
long periods of time
Can cause the tilting of
once vertical poles, fences,
and gravestones
Can break underground
pipes over time
FLOWS
Earth’s materials flow as if they were a thick liquid
Flows can move as slowly as a few km per year, or as rapidly as hundreds of km
per hour
Can be triggered by earthquakes or similar vibrations
SLIDES
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Rapid, down slope
movement of Earth’s
materials
Occurs when a relatively
thin block of loose soil,
rock, and debris
separates from the
underlying bedrock
(landslide)
Sometimes, a thick sheet
of rock moves downhill on
a sliding surface
(rockslide)
SLUMPS
When a mass of material in a landslide rotates and slides along a curved surface
May occur in areas with thick soils, on moderate to deep slopes
Common after rains as weight of additional water pulls material downhill
Leaves crescent-shaped scars on slopes
AVALANCHE
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Landslides that occur in
mountainous areas with thick
accumulations of snow
Caused when the Sun melts
surface of the snow, temperatures
drop and it refreezes into an icy
thin layer. Then more snow
accumulates on top of the icy
layer, which builds up and
becomes more heavy…
eventually causing it to slide
down slope at speeds up to
300km/hr
Usually occur on a slope of at
least 35o
About 10,000 occur each year in
the western USA alone
ROCK FALLS
Occur at high elevations, steep road cuts, and rocky shorelines where rocks are
loosened by physical weathering.
As rocks break up, they fall directly downward
Less common in humid areas, due to thick soil and vegetation
Section 8.2
Wind
Wind erosion is most severe in dry and coastal areas, where
there is little vegetation.
Unlike water, wind can move these materials uphill.
Wind can modify and change landscapes in arid and coastal
areas.
Wind cannot move materials as large as moving water can,
with exception to cases involving a hurricane or tornado.
Wind Erosion and Transport
Did You Know?
Wind Transport and
Erosion primarily
occur in areas with
little vegetative
cover, such as
deserts, semi-arid
areas, seashores,
and some
lakeshores.
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The ability of wind to erode materials is
less than that of other erosional agents.
Winds transport materials by causing
their particles to move in different ways.
Methods of wind transport:
 Rolling
motion along the ground
 Airborne, for long distances (suspension)
 A bouncing motion of particles (saltation)
Words to Know…
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Deflation – the lowering of the land surface that
results from the wind’s removal of surface particles
(smaller leave / larger remain)
Abrasion – occurs when particles rub against the
surface of other rocks to wear them down much like
sandblasting
Ventifacts – rocks that are shaped by wind-blown
sediments
Loess – thick, wind-blown silt deposits located in
Illinois, Iowa, Missouri, South Dakota, Nebraska,
Kansas, and Idaho
Barrier Islands

One of the world’s most
famous barrier islands,
the Outer Banks of North
Carolina, are formed
because sand is
repeatedly picked up,
moved, and deposited by
the currents of the
Atlantic Ocean.
Wind Deposition
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Formation of Dunes
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In wind-blown environments,
sand particles tend to
accumulate where an object
blocks movement
As this happens, particles
accummulate around the
object, causing a dune
The dune will appear to shift
as the wind shifts direction
On the dune, the gently sloped
side is the windward side and
the steep slope side is
referred to as the leeward
side
Appear when sand, high winds
and vegetation are present
Types of Dunes
BARCHAN
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Solitary, crescentshaped
Form in flat areas with
little sand or
vegetation
Most common dunes
TRANSVERSE
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Formed in areas with
lots of sand but little
vegetation
Forms in areas of
strong, steady,
prevailing winds
Forms in “ripples”
PARABOLIC
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U-Shaped dunes
Moderate winds and some
vegetation
Formed by winds blowing off
the water toward the shore
Protects against beach and
coastal erosion
Act as buffers against waves
and shelter for vegetation
Common on sea coasts
LONGITUDINAL
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Dunes parallel to the
wind direction
Forms in areas with
high, variable winds
and little sand
Form the highest,
longest dunes
Dune Restoration
Human activities have disrupted dune growth and damaged dune areas in many
parts of the United States. This has led to increased beach erosion and flooding
near the shorelines. Dune restoration areas, as shown above, seek to restore and
protect coastal area dunes. North Carolina is famous for its protected dunes and
shorelines.
Section 8.3
Glaciers
A large, moving mass of ice is called a glacier.
Glaciers covered 30% of the earth during the last Ice Age, which began about
1.6 million years ago.
Glaciers form near the poles and in mountains at high elevations, where
temperatures to not get above freezing all year and snow accumulates, never
melting.
The snow eventually gets thick enough, accumulating in an area called a
snowfield, that the pressure from the layers will increase temperatures at the
bottom enough to make a slippery mud.
The snow then recrystallizes to form ice, it breaks off, and the glacier is “on the
move.”
Types of Glaciers
Valley Glaciers
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Form in valleys in high,
mountainous areas
The speed of the glacial
movement is affected by the
slope of the valley floor, the
temperature / thickness of the
ice, and the shape of the valley
walls
Widen V-shaped stream valleys
in U-shaped glacial valleys
Movement is extremely slow,
usually less than a few
millimeters a day!
Continental Glaciers
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Glaciers that cover broad,
continent-sized areas
They form under the same
climatic conditions as valley
glaciers (but move in a different
way)
Continental glaciers are thickest
at the center, which forces the
rest of the glacier to flatten out
in all directions
Also referred to as “ice sheets”
Confined to Greenland, northern
Canada, and Antarctica
Glacial Erosion
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Glaciers are the most powerful of all erosional
agents because of their size, weight, and density.
As glaciers move, they pick up pieces of rock and
drag them along the bottom (like tines on a rake),
creating scratches
 Smaller
scratches are called striations
 Larger scratches are called grooves
Features Created by Glacial Erosion
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Cirques
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Arete
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Where two cirques on
opposite sides of a valley
meet, they form a sharp,
steep ridge
Horn
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Deep u-shaped valled
depressions
Where there are three or
more sides of a mountaintop,
a steep pyramid-shaped
peak forms
Hanging Valley
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A tributary valley that enters
a U-shaped valley from high
up a mountain side
Glacial Deposition Features
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Till
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Moraines
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Glaciers that move over older moraines from these landforms whose slope faces
the direction from which the glacier came
Eskers
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The area at the leading edge of the glacier, where the meltwater streams flow
and deposit outwash
Drumlins
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Ridges consisting of till deposited by glaciers as it begins to melt
Outwash Plain
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The sediments that are imbedding in the glacier’s tops, sides and edges. As the
glacier melts, this is left behind
Long winding ridges of sediments that are deposited by streams flowing under a
melting glacier
Glacial lakes
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Large blocks of ice break off a glacier, later are covered by sediments, and
then leave behind a hold called a kettle hole. This hole then can fill in with
meltwater to form a kettle lake