SECTION 2

Explain the advance and retreat of glaciers and the main features resulting from the processes of erosion and deposition by glaciers.

WHY DOES THIS HAPPEN?

WHAT ARE THE LANDFORMS?

WHAT PROCESSES

OCCUR?

Glaciers are always moving…

Glacier Long Profile

ZONE OF EXCESS

ZONE OF DEPLETION

GLACIAL MOVEMENT

ACCUMULATION > ABLATION = ADVANCEABLATION > ACCUMULATION = RETREATACCUMULATION = ABLATION = STEADY

GLACIAL REGIMES

HIGH ALTITUDES

SNOUT

ACCUMULATION (an input)As snow accumulates, it is buried under additional snow and becomes compacted.As this occurs, air is squeezed out, and the snow becomes ice.

Snowflakes: 5% water; 95% air.Granular Snow: 50%; 50%.Firn: 75%; 25%.Glacier Ice: 80-95%; 5-20%.

•MELTING-• EVAPORATION-•CALVING-•WIND EROSION- •AVALANCHE-

ABLATION (an output)

Change in state from solid to liquid as a result of heat through sunlight and friction.

Change in state from liquid to a gas / vapour as a result of heating by sunlight.

A glacier with a terminus that ends in a body of water (river, lake, ocean) into which it breaks up into icebergs.

The movement of material by the wind from the lifting power of moving air.

A rapid flow of snow, ice and meltwater that has become destabilised on the mountainside.

GLACIAL EROSIONPlucking is when melt water from a glacier freezes around lumps of cracked and broken rock. When the ice moves downhill, rock is plucked from the back wall.

Abrasion is when rock frozen to the base and the back of the glacier scrapes the bed rock.

Freeze-thaw is when melt water or rain gets into cracks in the bed rock, usually the back wall. At night the water freezes, expands and causes the crack to get larger. Eventually the rock will break away.

LANDFORMS OF GLACIAL EROSION

USE THE HANDOUTS AND IMAGES TO DESCRIBE AND EXPLAIN THE FORMATION OF THESE LANDFORMS OF EROSION.

CIRQUEARETESHORN (aka PYRAMIDAL PEAK)BERGSCHRUNDHANGING VALLEY

LANDFORMS OF GLACIAL DEPOSITION

• MEDIAL MORAINES• LATERAL MORAINES• END (TERMINAL) MORAINES

• ERRATICS

• DRUMLINSTILL

P174-175