glaciers
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Glaciers. Explain how glaciers move. Compare and contrast glacial erosion and deposition. Glaciers. Glaciers. Glacier: Large mass of ice and snow moving on land under its own weight. Glaciers. Glaciers are agents of erosion. - PowerPoint PPT PresentationTRANSCRIPT
GlaciersGlaciers• Glacier: Large mass of ice and
snow moving on land under its own weight.
GlaciersGlaciers• Glaciers are agents of erosion.
• Glacial erosion and deposition change large areas of Earth’s surface.
• As glaciers move forward over land they can transport huge volumes of sediment and rock.
GlaciersGlaciers• How do glaciers move?
• The weight of the glacier causes the ice to flow outward like pancake batter on a griddle.
GlaciersGlaciers• Plucking: process that adds gravel,
sand, and boulders to a glacier’s bottom and sides as water freezes and thaws, breaking off pieces of surrounding rock.
GlaciersGlaciers• These plucked rock fragments and sand at a
glaciers base scour and scrape the ground below like sandpaper against wood.
• Glacial striations.
GlaciersGlaciers• When glaciers melt they can no longer
carry much sediment.
• The sediment is deposited on land.
• As the glacier retreats it leaves a mixture of boulders, sand, clay and silt
called till.
GlaciersGlaciers• Till deposits can cover huge areas of land.
• Enough till has been left behind in the U.S. to fill valleys completely.
• Iowa, Montana, parts of Ohio, Indiana, Illinois and New England contain till.
GlaciersGlaciers• Moraine deposits: Rocks and soil
deposited at the end of a glacier creating a ridge. – These deposits occur much like a grocery
store conveyor belt as it piles up items at its end.
• Outwash: material deposited by the meltwater from a glacier.
• Eskers: outwash deposits resulting in winding ridges of gravel and sand.
GlaciersGlaciers
Types of GlaciersGlaciers• Continental Glaciers:
– Cover 10% of the Earth.
– Mostly near the poles.
– Huge masses of ice and snow.
Types of GlaciersGlaciers• Continental glaciers in the past covered
28% of the Earth.
• This period was known as the Ice Age.
Types of GlaciersGlaciers• Glaciers have advanced many times
during the last 2 million to 3 million years.
• The last major advance of glaciers was about 18,000 years ago.
Types of GlaciersGlaciers• Valley Glaciers: Occur in high
mountains where the average temperature is low enough to prevent snow from melting.
• Valley glaciers grow and creep along.
Types of GlaciersGlaciers• Valley glaciers erode mountains creating
valleys.
• Glacially eroded valleys are U-shaped.
• Stream eroded valleys are V-shaped.
GlaciersGlaciers• Question: How do glaciers cause
erosion?
Rock fragments and sand scour the soil and bedrock eroding the ground below.