Glacial Erosion and Depositional Features

How Do Glaciers Affect the Landscape?

Glacial Erosion

• Glaciers remove loose rock from the valleys• The flowing glacier pries rocks loose and

incorporates them into the ice

Glacial Striations

• Rocks scrape the underlying bedrock• This picture was taken near Squamish 1997

Valley Shape

• Glaciers will carve out a U shaped valley

• A fjord is a U shaped valley filled in with water. It’s also called an inlet.

Fjords and InletsSognefjord, Norway

Erosional Features

• At the top of an alpine glacier a semicircular basin is carved out called a cirque

• When two cirques form on a peak the ridge separating them is called an arête

• Three or more cirques on a mountain can carve out a horn

The glacier erodes

After the glacier melts

The Matterhorn

In the Swiss alps

• A Swiss glacier is eroding the mountain.

Glacier at work

Swiss Alps are glacially sculpted

Glacial Deposits

• Glaciers pick up everything in its path, even the largest boulders.

• Large amounts of sediment can be carried large distances by glaciers.

• Glacial deposit is called till.

Erratics

• Erratics are large boulders carried and then deposited by a glacier.

• It marks the furthest extent of the glacier.• Near 12th Avenue and 200th Street, Surrey.

Glacial Erratics

Estonia, Gulf of Finland. These rocks were carried and deposited by glaciers from Finland to Estonia

• Burnaby Mountain ParkGlacial Erratics

Moraines

• A moraine is a mound or ridge of till deposited by a glacier

• The different places along a glacier’s advance will result in the different types of moraines

CL

Moraine dams the lake

• Banff National Park• The haze is from the

forest fires of 2003

Moraine Lake

• Bluest lake in the Rockies. The glacial till causes the light to be scattered leaving the lake very blue.

Peyto Lake

• End moraine of the Matanuska Glacier, Alaska. • Note the poorly sorted sediment; The boulders are

several meters in diameter.

End Moraine

• The terminus of a glacier may remain stationary for years.• The sediment piles up in a ridge called an end moraine.• If this marks the furthest extent of the glacier it is a

terminal moraine.

Formation of end moraine

Retreating Glacier

End moraine

The retreating Athabasca GlacierJasper National Park, Alberta

On the Athabasca GlacierGlaciers are full of dirt, and there are crevasses.

Lateral Moraine

• Lateral moraines are accumulations of sediment on the margins of glaciers.  • Rock slides, rock falls, snow avalanches and other forms of mass wasting are

especially efficient at loading the margins of the glacier with this material. 

Formation of a Medial Moraine

• The medial moraine forms where two tributary glaciers meet, and their adjacent lateral moraines merge to form the medial moraine.

Kennicott Glacier, Alaska.

Medial Moraine

At least how many tributary glaciers must there be to create this formation?

Three, because there are two medial moraines

• Switzerland, Aletsch Glacier in the Bernese Oberland