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

Fjords and Inlets

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

Sognefjord, 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

Glacier at work

• A Swiss glacier is eroding the mountain.

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 12^th Avenue and 200^th Street, Surrey.

Glacial Erratics

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

Glacial Erratics

• Burnaby Mountain Park

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

Moraine dams the lake

CL

Moraine Lake

• Banff National Park
• The haze is from the forest fires of 2003

Peyto Lake

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

End Moraine

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

Formation of 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.

Retreating Glacier

End moraine

The retreating Athabasca Glacier

Jasper National Park, Alberta

On the Athabasca Glacier

Glaciers 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

• Switzerland, Aletsch Glacier in the Bernese Oberland

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

Three, because there are two medial moraines