Chapter 7.1b Glaciers

Landforms Created by Glacial Erosion Glaciers produce things like glacial troughs, hanging valleys, cirques, aretes, and horns.

Glaciated Valleys A glacier will wide, deepen, and straighten a once narrow valley. It changes it from a V- shaped valley to a U-shaped glacial trough. The amount of glacial erosion depends on the thickness of the ice. This produces an area with higher valley walls that produce big waterfalls.

Cirques This is a bowl-shaped depression at the head of a glacial valley that is surrounded on 3 sides by steep rock walls. They form where snow and ice accumulate at the head of a valley glacier.

Aretes and Horns Aretes are snaking, sharpedged ridges. Horns are pyramid-like peaks. The Matterhorn in Switzerland is an example of a horn.

Glacial Deposits When a glacier melts it deposits sediment.

Types of Glacial Drift Glacial drift is all sediments of glacial origin, no matter how, where, or in what form they were deposited. There are 2 types: Till is material deposited directly by the glacier. These are usually unsorted mixtures made of many different particle sizes. Stratified drift – this is sediment laid down by glacial melt water. They are sorted according to size and weight of the debris. It is made of a lot of sand and gravel.

Moraines, Outwash Plains, and Kettles This are all depositional features. When glaciers melt they leave layers or ridges called moraines.

Lateral Moraines Lateral moraines are ridges that form along the sides of glacier valleys when the glacier melts and leaves material that it has gathered. Medial moraines are when 2 valley glaciers joint to form a single ice stream.

End Moraines and Ground Moraines When a glacier doesn’t move for a long period of time the ice is still flowing in the glacier and it moves rock and material to the end of the glacier, the deposits are called an end moraine. Ground moraines occur when a glacier begins to recede. The front of the glacier melts and leaves sediment.

Outwash Plains This is when a glacier is melting and the sediments accumulate and make an ice sheet called an outwash plain.

Kettles These are depressions and small lakes.

Drumlins and Eskers Drumlins are hills made of till. It will have a steep side that faces the direction the ice came from and a gentler slope that points in the direction the ice moved. Eskers are snake-like ridges made of sand and gravel.