chapter 12:agents of erosion & deposition section 3...

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Chapter 12:Agents of Erosion & Deposition

Section 3: Erosion & Deposition by Ice


Chapter 12

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.

• 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.”

Section 3 Erosion and Deposition by Ice


Chapter 12

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.



Chapter 12


• 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.



Chapter 12

• 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.




Chapter 12

• 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.




Chapter 12

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.



Chapter 12

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.



Chapter 12

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.



Chapter 12

Types of Glacial Deposits, continued • Stratified drift is a glacial deposit that has been

sorted and layered by the action of streams or

meltwater.

• Streams carry sorted material and deposit it in front

of the glacier in a broad area called an outwash

plain.

• 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.


chapter 12:agents of erosion & deposition section 3...

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