World GeographyWorld Geography

Unit 1: Land and Water FormsUnit 1: Land and Water Forms

Glaciers as Agents of ErosionGlaciers as Agents of Erosion

GlaciersGlaciers

What Are Glaciers?What Are Glaciers?

• Glacier: Large sheet of ice that flows like a river under the influence of gravity.

• Today 1/10 of Earth’s land surface is covered by ice

• 10000 years ago it was nearly 1/3

• Thus ice has had a huge impact on the physical world we see today

Types of GlaciersTypes of Glaciers

• The glaciers that we see today are of two different types.– Alpine Glaciers: Glaciers that form high in

mountain valleys above the snowline.– Continental Glaciers: Large sheets of ice that

cover portions of the continental land mass.

DifferencesDifferences

• Continental and Alpine Glaciers differ in two ways:– Location: Alpine glaciers are only found on

mountains whereas continental glaciers are only found and the earth’s poles regardless of elevation

– Size: Alpine glaciers are smaller compared to continental glaciers.

SimilaritiesSimilarities

• They both move and cause erosion

• Both types change the features of the landscape

• Both developed in the same way; bodies of water subjected to constantly cold temperatures below freezing for very long periods of time.

The Last Ice AgeThe Last Ice Age

The Last Ice AgeThe Last Ice Age

Ice Cover TodayIce Cover Today

How Do Glaciers Grow?How Do Glaciers Grow?

• Glaciers can be seen as an open system– Input – Snow– Output – Ice, meltwater, and water vapor

• At its upper end the glacier is fed by snow this area is known as the accumulation zone

• If a Glacier receives more input than it loses in output the glacier grows.

• Accumulation Zone: where a glacier grows• Ablation Zone: Where a glacier loses mass

How Does a Glacier Move?How Does a Glacier Move?

• The movement of a glacier has much to do with the properties of the ice that makes up the glacier

• At different depths glacial ice has different properties, and behaves in different ways

• At the top it is solid, much like ice in a freezer, however deep within the glacier the ice is plastic, more like a frozen jelly

• This plastic ice distorts itself, and flows in response to the upper layers of ice, and the slope of the land

Glacial Mass and BalanceGlacial Mass and Balance

Depositional Glacier TermsDepositional Glacier Terms

• The following is a list of terms that are useful in talking about glaciers– Outwash plain– Terminal Moraine– Erratic– Drumlin– Esker

Outwash PlainOutwash Plain

Outwash plain: Glacial stream deposits of stratified drift or melt-water fed, braided and overloaded streams; occurs beyond a glaciers moraine deposits.

Terminal MoraineTerminal Moraine

• Terminal Moraine: Eroded debris that is dropped at a glacier’s farthest extent; forming a ridge like structure

ErraticErratic

• Erratic: a piece of rock that deviates from the size and type of rock native to the area in which it rests. These rock are carried by glaciers and deposited when they melt.

ErraticErratic

• A piece of rock that is left behind by a glacier, that is obviously not like the surrounding rocks.

• As glaciers move they pick up large chunks of rock, as they melt the rocks are left behind.

DrumlinDrumlin

• Drumlin: A depositional landform related to glaciation that is composed of till (unstratifeid, unsorted eroded material) and is streamlined in the direction of continental ice movement; blunt end upstream and tapered end down stream with a rounded top.

DrumlinDrumlin

EskerEsker

• Esker: A curving, snakelike, narrow deposit of coarse gravel that forms along a melt-water stream channel developing in a tunnel beneath a glacier.

EskerEsker

Evidence of MovementEvidence of Movement

• There are three things to look for when trying to determine the direction of movement of a glacier:– The gently sloped end of drumlins point in the direction

of glacier movement

– The terminal moraine marks the furthest edge of the glacier

– The layers of silt in an outwash plain can indicate the direction of glacier movement. Fine particles would be at the leading edge while larger particles would have been closer to the glacier.

Erosional LandformsErosional Landforms

• Alpine glaciers create spectacular, dramatic landforms that bring to mind the Canadian Rockies.

• Some of these features include;– Cirque– Arête– U-Shaped valley– Hanging valley– Terminal Moraine

CirqueCirque

• Cirque: A scooped-out, amphitheater-shaped basin at the head of an alpine glacier valley.

ArêteArête

• Arête: A sharp ridge that divides two cirque basin. Derived from “knife edge” in French, these form sawtooth and serrated ridges in glaciated mountains.

U-Shaped ValleyU-Shaped Valley

• U-Shaped Valley: Large deep valley created by the main glacier in a flow gouging down deep into the bedrock

Hanging ValleyHanging Valley

• Hanging Valley: Like a tributary to a river a hanging valley consists of a smaller ice flow that runs into the main glacier. It gets its name because it does not carve as deep into the ground, resulting in a valley at a higher altitude

Terminal or End MoraineTerminal or End Moraine

• Terminal moraine: Eroded debris that is dropped at a glacier’s farthest extent

Lateral MoraineLateral Moraine

• Lateral Moraine: Debris transported by a glacier that accumulates along the sides of the glacier and is deposited along the margins.

FjordsFjordsFjord: A drowned glacial

valley near the coastline• Formation

– A large glacier erodes troughs and valleys in mountains extending to the coast

– Carving a large U shaped valley

– When the Glacier melts seawater floods the valley