Glacier Movement: How Glaciers Move

The weight of overlying layers of ice and snow push down on the lower layers of the glacier.

This causes melting and refreezing, and thus movement downhill

Some glaciers move only a few cm’s per day, others move as much as 3000 cm per day.

Glacial valleys have steep and gentle slopes.

When a valley glacier comes to a steep slope, great fissures called crevasses form across the width of the glacier.

Glaciers Move

Glaciers become thinner as they move lower due to melting and evaporation.

The glacier ends at its ice front. Many glaciers worldwide have receding ice

fronts, as the glacier melts faster than it moves forward.

In Alaska and Greenland, many glaciers reach the sea and great blocks break off to become icebergs in a process called calving.

In Antarctica, the ice may extend under water in ice shelves.

Glacier Calving in Alaska

Glaciers Transport Loose Rock

Glaciers remove loose rock from the valleys through which they move.

Particles range in size from fine powder to giant boulders. Rock flour is a mix of fine sand and silt formed under a glacier.

Large amounts of rock material build up in several areas of a moving glacier.

When these materials are deposited they form moraines.

There are: ground moraines (under glacier), lateral (side) moraines, medial (middle) moraines, and end moraines (at the ice front).

Erosion by Glaciers

Glaciers erode mostly because of pieces of rock that are dragged over the bedrock and act as cutting tools.

Long scratches called striations are left on the rock, and show the general direction of ice movement.

Bedrock can be shaped into many forms by glaciers.

Bedrock may become smooth and polished, or steep and rough.

Roches moutonnées are rough outcrops. Potholes may form from meltwater forming

whirlpools under a crevasse.

Roche moutonnées

Frost action and glacial erosion wear away the walls of mountain peaks.

A semicircular basin called a cirque is formed at the head of a glacial valley.

When two cirques are formed next to each other they can create a narrow and sharp divide, called an arête.

When three or more cirques cut into the same peak they can create a pyramid shaped peak, called a horn.

Glacial Valleys

A valley glacier touches the entire valley and most of the walls.

The glacier scours away the rock until it flattens the entire valley floor and make the walls nearly vertical, creating a glacial trough.