GlaciersGlaciers• Explain how glaciers move.

• Compare and contrast glacial erosion and deposition.

GlaciersGlaciers

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• Glacial grooves occur when bedrock is

gouged deeply by rock fragments.

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.

Glacial TillGlacial 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.

Types of GlaciersGlaciers

Valley glaciersValley glaciers

GlaciersGlaciers• Question: How do glaciers cause

erosion?

Rock fragments and sand scour the soil and bedrock eroding the ground below.

GlaciersGlaciers• http://www.unique-southamerica-travel-

experience.com/glaciers-national-park.html• http://theresilientearth.com/?q=content/

himalayan-glaciers-not-melting• http://www.grid.unep.ch/glaciers/

graphics.php• http://www.sup.org.uk/

moving_mountains.htm