Glaciers

I. Glaciers are thick masses of ice that move slowly

A. The movement of a glacier is called FLOW

B. Plastic Flow is the movement within the ice

1. when the pressure or load of ice is over 50 meters the layers of ice slide over each other

C. Basal flow or Basal Slip is when melt water from the glacier acts as a lubricant and helps the ice flow over rocks

II. Types of Glaciers

A. Valley – forms at high elevation where snow or ice lasts year after year

1. They take over valleys of river systems

B. Continental – forms over large expanses of land

C. Piedmont – when a valley glacier extends to a plain

III. Erosion by glaciers

A. Glacial Erosion occurs by abrading and plucking

1. Abrading is the scouring of bedrock by the ice

2. Plucking is caused by the meltwater seeping into cracks, freezing and expanding which will wedge blocks of rock loose along with other fragments

B. The movement of the glacier and the substances “stuck” to the bottom will cause long parallel lines called striations

C. Cirques will form, and the small round basin like depression will open and one side and allow the glacier to pour out.

1. When several cirque3s form around a mountain, then erode themselves, a horn can be formed; this type of mountain is usually a sharp jagged peak such as the Matterhorn

D. Erosion by glaciers

1. river erosion is usually V shaped

2. glacial erosion is usually U shaped

IV. Glacial Deposits occur as a glacier melts and leaves several types of deposits

A. Till – the first material dropped as a glacier melts; usually a jumble of boulders, sand and clay

B. Outwash – sorted material that is deposited in layers much like river deposits

C. Terminal Morains – ridges of till formed when the glacier is moving at the same pace as it’s melting

D. Ground Morain – when the ice melts faster than the glacier moves