section 15.2 glacial movements and erosion. how do glaciers move? what are some reasons why glaciers...

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”