Section 15.2Glacial Movements and Erosion

How do glaciers move?

What are some reasons why glaciers move?

• Heavy snow fall

• Steep slopes

• Temperature increase/summer

What slows glaciers down?

• Friction

Slip and slide on a layer of water (friction)

2 main types of glacial movement

1. Basal slip

2. Plastic flow

1. Basal slip

• Basal slip = immense weight of the glacier puts pressure on the bottom causing grains of ice to partially melt

– creates a slushy layer– glacier “slips and slides” on the slush

2. Plastic Flow

• Due to pressure (weight) of snow above

• Grains of ice actually deform and flatten

• Ice in the interior of the glacier moves forward like a plastic putty

As a glacier moves…Crevasses form

• cracks in the glacier due to increased speed often associated with a steep incline

What happens at the end of a glacier?

If the glacier is below the snowline…

ice front -the ice starts to melt, signifying the end of the glacier

What happens at the end of a glacier?

If the snowline is at sea level…

calving -large pieces of glacier break off of the front (icebergs!)

How do glaciers cause erosion?

Till -breaking down boulders, rocks, pebbles, and small grains into smaller pieces

Moraine -the accumulation of till

The Ransom Moraine is a

large moraine that

cuts diagonally

across Kendall County

Aftermath of glaciers

Striations -occur when the glacial load scratches parallel groves in the underlying bedrock

Roches mountonnees

a distinct pattern of rocks that are often exposed that bare a resemblance to a flock of sheep. “sheep rocks”