Chapter 3

Section 4

Glaciers

Glaciers

•Moving mass of ice and snow

•Form when more snow falls than melts

Agent of erosion

GlaciersAdvancing Glacier-When the glacier increases in size and slides forward due to gravity

Retreating Glacier-When the glacier decreases in size because it is melting

2 Kinds of

Glaciers

Muddy River

Glacier, Alaska 1948

Valley Glacie

r(Alpine

)

•Located in mountainous areas

•Snow and ice build up in a long, narrow v-shaped river valley

Continental Glacier

• Huge mass of ice and snow (larger than valley glacier)

• Usually covers a large portion of land like a continent

• Only tallest peaks of land are exposed

• Today cover 10% of earth's surface (found in Greenland & Antarctica)

What is NOT a glacier?

• are in water, not on land

• are much smaller than glaciers

• About ⅞ of an iceberg is below the water line.

Last Ice AgeWhite is land covered in ice.

You are here.Continental glaciers cover large portions of the world at one time

http://cabrillo.edu/~crsmith/glacloop.gif

Last Ice AgeBlue is land covered in ice.

You are here.

Person

Leading Edge of Glacier

1. Snow accumulates and piles up faster than it melts

2. Weight of snow is great enough to compress bottom layers into ice

3. Ice on bottom partially melts and becomes putty like

4. Whole mass begins to slide on this putty-like layer

5. When the mass of the glacier is too great, gravity pulls

How do glaciers form and move?

How do glaciers erode Earth’s surface?

Abrasion & PluckingPlucking-Glacier picking

up rocks as it travelsAbrasion-Glaciers gouge and scratch land below as it moves

How do glaciers erode Earth’s surface?

•As they move, glaciers act as bulldozers pushing loose material out of their path

•These eroded sediments are added to the mass of the glacier (plucking) or piled up along its sides

•Glaciers also grind rock and soil that isn't loose (abrasion)

StriationsThe “stripes” scratched into rocks by glacial abrasion.

How do glaciers deposit sediment?

MoraineWhere a glacier deposits mounds or ridges of till (sediment)

Terminal Moraine

The ridge of till at the farthest point reached by a glacier (Long Island & Cape Cod-terminal moraine from last ice age)

How do glaciers deposit sediment?•Glaciers begin to melt and lose their energy of motion

•Begin to deposit sediments they carry (till )

•Till at the edges of a glacier (moraine)

•Till at the end of a glacier (terminal moraine)

How do glaciers shape the land?What kinds of glacial landforms

are created?

Kettle Lake FormationKettle-small depression formed by a chunk of glacial ice left behind

Kettle Lake Contain water all year long

Kettle lake- kettle that fills with water from melted ice blocks

Glacial LakeGlacial lake- Forms like a kettle lake, but high in the

mountains

Contain water all year long

Horn-mountains with sharp pointed peaks

Arête-sharp edges that run down mountain sides (separating 2 cirques)

Cirque-a bowl-shaped hollow in mountain side where glacier began

U-shaped valley- a valley carved by glaciers in U-shape, usually from a v-shaped river valley

Fiord (Fjord)Fiord- a coastal valley cut by glacier that fills in with water when seas rise from glacial melt

Glacier Direction of

flow

Drumlin-mounds of till that a glacier slides over and as the glacier melts back the mound becomes uneven

Glacier Features

The following photos are

courtesy of a former student’s family vacation to

Alaska

What am I showing you?

Where a glacier makes an ICEBERG

What am I showing you?

The TILL from plucking & abrasion that will be laid down when the glacier melts

What am I showing you?

The carving power of a glacier

U-SHAPED VALLEY, HORN, ARÊTE

What am I showing you?

Drumlin -Which direction was the glacier flowing?

What am I showing you?

Glacial Lake

What am I showing you?

Valley Glacier