Chapter 12 Section 3 Erosion and Deposition by Icedodgenms.typepad.com/files/chapter-12-section-3-glaciers.pdf · Chapter 12 Section 3 Erosion and Deposition by Ice ... • Valley

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Chapter 12 Section 3

Erosion and

Deposition by Ice


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.


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—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.”


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.




• 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.


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 )



• 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.



Movement of Glaciers

Click below to watch the Visual Concept.

Visual Concept

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80180.html


• 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.



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.




Horn ~ residual,

isolated,

pyramid-shaped

peak, caused by

the headward

erosion of

several glaciers


Cirque ~ a hollowed-out bowl-shaped

depression at the head of a glacial valley


Arête ~ sinuous, sharp-edged ridge


Hanging valley and waterfall


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.


GL ACIAL TIL L I S TYP ICAL LY U NSTRATIF IED AND UNSORTED.


GLACIAL T ILL ~ MATERIAL THAT IS DEPOSITED

DIRECTLY BY THE ICE. IT IS UNSORTED.


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.




• Stratified drift is a glacial deposit that has been

sorted and layered by the action of streams or

meltwater.


STRATIFIED DRIFT



• Streams carry sorted material and deposit it in front

of the glacier in a broad area called an outwash plain.


OUTWASH PLAINS



• 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.


Kettle


Glacial Drift: Stratified Drift and Till

Click below to watch the Visual Concept.

Visual Concept

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80184.html




Chapter 12 Section 3 Erosion and Deposition by Icedodgenms.typepad.com/files/chapter-12-section-3-glaciers.pdf · Chapter 12 Section 3 Erosion and Deposition by Ice ... • Valley

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