Chapter 12 Glaciers

What conditions are necessary to form a glacier?

1) Cold local climate (2) snow must be abundant (3) snow must not be removed by avalanches or wind.

percent of earth covered by glacials

10%

The last episode of widespread continental glaciation in North America was at its peak

18,000 years ago

How do glaciers deposit sediment

As a glacier moves or expands, it transports a vast amount of sediment—a mix of boulders, small rocks, sand, and clay. It acts like a plow, pushing rock and soil and plucking out big blocks of rock.

plucking

Boulders get frozen into basin of glacier and as glacier moves it plucks the rock with it

How does the eroded landscape beneath glaciers differ from that developed in rock exposed above glaciers?

Erosion above glaciers: constant minute losses from wind and water, heating and cooling. Erosional losses below glaciers: gross grinding rocks carried along by the ice

The boundary between the zone ablation and the zone of accumulation is called:

The equilibrum line

How do glaciers move?

This solid crystalline material deforms (changes) and moves. Glaciers, also known as "rivers of ice," actually flow. Gravity is the cause of glacier motion; the ice slowly flows and eforms (changes) in response to gravity.

glacially curved valleys are usually shaped like a...

U

continental glaciation

exists where a large part of a continent is covered by glacial ice

how fast does the central part of a valley glacier move compared to the sides of the glacier

faster

alpine glaciation

found in mountainous regions

Types of moraines

ground moraine, lateral moraine., recessional moraine.

what is not a type of glacier

sea ice

In a receding glacier

the equilibrium line lowers

faster a glacier moves

the more erosion it does

What does the presence of glaciers on Earth tell us about climate?

trapped air bubbles, which reveal past atmospheric composition, temperature variations, and types of vegetation.