GLACIATION

GLACIERS

• Definition–a slowly moving mass or

river of ice formed by the accumulation and compaction of snow on mountains or near the poles

GLACIERS• At any place on the land where more snow

accumulates than is melted during the course of a year, the snow will gradually grow thicker.

• As the snow piles up, the increasing weight of snow overlying the basal layers causes them to recrystallize, forming a solid mass of ice.

• When the accumulating snow and ice become so thick that the pull of gravity causes the frozen mass to move, a glacier is born.

HOW IS A GLACIER FORMED?

• Ice crystals grow & join together to form solid sheets

90% air

50% air

ALPINE GLACIER: • a glacier found in a mountain range

• forms because of the continual snow build-up in mountainous areas

ALPINE GLACIER

ALPINE GLACIER

Alpine Glaciers Make Land Rugged

CONTINENTAL GLACIER• A continuous mass of unconfined ice, covering

at least 50,000 square km• Most extensive at present as ‘ICE SHEETS’

covering Greenland and Antarctica

Continental Glaciers Round the Landscape

EROSIONAL FEATURES OF GLACIERS

• Straitions

Geological Survey of Newfoundland

GLACIAL DEPOSITS

• After eroding rock, glaciers leave “deposits”

• Glacial Drift: refers to all sediments of glacial origin

TILL

• material that is deposited directly by the ice

OUTWASH

• sediments laid down by glacial melt water

EROSIONAL FEATURESFINGER LAKES

•glaciers gouge out a strip of land in a narrow channel often where a river valley once existed

EROSIONAL FEATURESKETTLES

•Are hollows formed when giant blocks of ice were buried in the till

EROSIONAL FEATURESFJORDS

•Flooded U-shaped valleys

FJORDS

EROSIONAL FEATURESCIRQUES

•Circular hollows on the upper slopes of mountains where alpine glaciers originated

EROSIONAL FEATURESARETES

•Ridges that are left when two cirques occur side by side

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horn

arete

cirque

DEPOSTIONAL FEATURESERRATICS

•A large, isolated boulder left behind by a glacier

ERRATIC

ICE AGE• An extended period of sub-zero

temperatures (10,000 years) where glaciers are found over large areas of land

ICE AGE• Most recent Ice Age ended

12,000 years ago (Wisconsin Ice Age)

GEOLOGIC TIMELINE

Era Time (millions of years ago)

Cenozoic 66 to today

Mesozoic 245 to 66

Paleozoic 570 to 245

Precambrian 4600 to 570

GLOBAL DISTRIBUTION OF GLACIERS• Occupy 10% of Earth’s surface

GREENLAND GLACIER

Nation Area (square kilometers)Antarctica* 11,965,000Greenland 1,784,000Canada 200,000Central Asia 109,000Russia 82,000United States** 75,000China and Tibet 33,000South America 25,000Iceland 11,260Scandinavia 2,909Alps 2,900New Zealand 1,159Mexico 11Indonesia 7.5Africa 10* (without iceshelves and ice rises)** (including Alaska)

Approximate Worldwide Area Covered by Glaciers