Lesson 30 - Glacial Processes and Landforms

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Types of glaciers

1. Mountain glaciers: Glaciers that form in mountainous areas.
• Highland icefiels
• Valley glaciers
• Alpine glacier
• Cirque glacier
2. Continental ice sheets: Glaciers from in non mountainous areas. The two main types are Antarctica and Greenland.

Accumulation

Addition of Ice by accumulation of snow

Glacial abrasion

Bedrock is worn down by the rocks being dragged along in the moving ice

Isostasy

term used in geology to refer to the state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates "float" at an elevation which depends on their thickness and density.

Glacial plucking

- Process of glacial erosion.
- Rock fractures open up beneath the glacier because of the weight of the ice and because of the freezing and thawing of water in cracks.
- The stress exerted by lowing glacial ice plucks rocks fragments loose and transports them in the direction of glacier flow.
- Particularly effective on leeward slopes and in well-jointed bedrock.

Drift

General term for all material moved by glaciers

Till

Rock debris deposited directly by moving or melting of ice, with NO meltwater redeposition involved

Moraine

- Process of glacial deposition
- General term for glacier-deposited landforms compsed entirely or largely of till.

Outwash plain

Smooth, flat alluvial aprons deposited beyond recessional or terminal moraines by streams issuing from the ice.

Glacial trough

- Glaciers move down valleys with more effectiveness than a stream.
- A valley shaped by valley glaciers and ice streams within ice sheets that has a distinct trough form.

Accumulation Zone

- Upper portion of a glacier.
- Here the amount of new ice added by snowfall exceeds the amount lost by melting an d sublimation

Ablation Zone

- Lower portion of a glacier.
- The amount of ice added is less that the amount lost

Terminal moraine

A ridge of till that marks the outermost limit of glacial advance

Glacial advance/retreat

Getting bigger or smaller due to relation between ablation and accumulation.

Glacial flow

Displacement of ice movement downslope. Always happen even when glacier is retreating

Glacial erosion

- Plucking
- Abrasion

Glacial landforms

- Horns
- Cirques
Roche moutonnée
Troughs
• U-shaped Valley
• Hanging valley
• Fjord

Glacial transportation

- Rock flour/loess
- Till
- Erratics (huge rock)

Glacial deposition

- Moraine
- Drumlin (elongated, linear feature-opposite of roche moutonnée)
- Outwash plain (sorted material)
- Kettle lakes (big chunk of ice melted)

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