Glaciers Glaciers v Glacier a thick mass of

Glaciers

Glaciers: v. Glacier – a thick mass of ice that forms over land from the compaction and recrystallization of snow and shows evidence of past or present flow

Types of glaciers • Valley/mountain/alpine glaciers – form in mountainous areas • Ice sheets or continental glaciers • Large scale • e. g. , Over Greenland Antarctica – Ice Caps: Small Ice sheets

Currently ice sheets cover Greenland Antarctica

Movement of glacial ice • Types of glacial movements • Plastic flow • Slipping along the ground • Zone of fracture • Uppermost 50 meters • Crevasses form in brittle ice

Movement of glacial ice • Zone of accumulation – the area where a glacier forms • Zone of wastage – the area where there is a net loss due to melting

Accumulation and Wastage Figure 6. 7

Glacial Erosion • Plucking – Gouging out and lifting of chunks of rocks • Abrasion – Striations (scratches and grooves in the bedrock)

Landforms created by glacial erosion • • • Glacial trough Hanging valley Cirque Arête Horn Fjord

Erosional landforms created by alpine glaciers

The Matterhorn in the Swiss Alps

Glacial deposits • Glacial drift • Till – material that is deposited directly by ice • Stratified drift – sediment deposited by water melting off surface of glacier

Glacial till is typically unstratified and unsorted Figure 6. 13

Close-up view of the boulder in the previous slide

Glacial deposits • Depositional features – Moraines – layers or ridges of till – Types of moraines • Lateral • Medial • End • Ground

Glacial deposits • Depositional features – Outwash plain or valley train – Kettles – Drumlins – Eskers – Kames

Glacial depositional features

Kettle lakes

• Ice Age • Began 2 to 3 million years ago • Division of geological time is called the Pleistocene epoch • Ice covered 30% of Earth’s land area

Maximum extent of ice during the Ice Age Figure 6. 22

Indirect effects of Ice Age glaciers • • Migration of animals and plants Rebounding of the crust Drop in sea level Climatic changes

Causes of glaciation • Variations in Earth’s orbit • Shape of Earth’s orbit varies • Angle of Earth’s axis changes • Axis wobbles