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Objectives
• Explain the difference between alpine glaciers and
continental glaciers.
• Describe two ways in which glaciers move.
• Identify five landscape features formed by alpine
glaciers.
• Identify four types of moraines.
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Glaciers—Rivers of Ice
• A glacier is a large mass of moving ice. They are
capable of eroding, moving, and depositing large
amounts of rock materials.
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Glaciers—Rivers of Ice
• Glaciers form in areas so cold that snow stays on
the ground year-round. Because glaciers are so
massive, the pull of gravity causes them to flow
slowly, like “rivers of ice.”
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Glaciers—Rivers of Ice, continued
• Alpine Glaciers form in mountainous areas. One
common type of alpine glacier is a valley glacier.
• Valley glaciers form in valleys originally created
by stream erosion. As these glaciers slowly flow
downhill, they widen and straighten the valleys into
broad U shapes.
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Glaciers—Rivers of Ice, continued
• Continental Glaciers are huge, continuous masses
of ice that can spread across entire continents.
• The largest continental glacier in the world covers
almost all of Antarctica. This ice sheet is approximately
one and a half times the size of the United States, and
is more than 4,000 m thick in some places.
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I C E S H E E T / C O N T I N E N TA L G L AC I E R :
( I M AG E S O F G R E E N L A N D I C E S H E E T )
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• Glaciers on the Move When enough ice builds up
on a slope, the ice begins to move downhill. Thick
glaciers move faster than thin glaciers, and the
steeper the slope, the faster the glaciers will move.
• Glaciers move in two ways: sliding and flowing. A
glacier slides when its weight causes the ice at the
bottom to melt. A glacier flows as ice crystals within
the glacier slip over each other.
Glaciers—Rivers of Ice, continued
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Movement of Glaciers
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Visual Concept
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• Glacier movement is affected by climate. As the
Earth cools, glaciers grow. About 10,000 years ago,
a continental glacier covered most of North America.
Glaciers—Rivers of Ice, continued
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Landforms Carved by Glaciers
• Continental glaciers and alpine glaciers produce
landscapes that are very different from one another.
• Continental glaciers smooth the landscape by
scraping and eroding features that existed before
the ice appeared.
• Alpine glaciers carve out large amounts of rock
material and create spectacular landforms.
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Horn ~ residual,
isolated,
pyramid-shaped
peak, caused by
the headward
erosion of
several glaciers
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Cirque ~ a hollowed-out bowl-shaped
depression at the head of a glacial valley
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Types of Glacial Deposits
• As a glacier melts, it drops all the material it is
carrying. Glacial drift is the general term used to
describe all material carried and deposited by
glaciers.
• Glacial drift is divided into two main types, till and
stratified drift.
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GLACIAL T ILL ~ MATERIAL THAT IS DEPOSITED
DIRECTLY BY THE ICE. IT IS UNSORTED.
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Types of Glacial Deposits, continued
• Till Deposits Unsorted rock material that is
deposited directly by the ice when it melts is called
till. Unsorted means that the till is made up of rock
material of different sizes.
• The most common till deposits are moraines.
Moraines generally form ridges along the edges of
glaciers.
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Types of Glacial Deposits, continued
• Stratified drift is a glacial deposit that has been
sorted and layered by the action of streams or
meltwater.
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Types of Glacial Deposits, continued
• Streams carry sorted material and deposit it in front
of the glacier in a broad area called an outwash plain.
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Types of Glacial Deposits, continued
• Sometimes, a block of ice is left in an outwash plain
when a glacier retreats. As the ice melts, sediment
builds up around the block of ice, forming a
depression called a kettle.
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Glacial Drift: Stratified Drift and Till
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Visual Concept