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.