Glaciation in Canada

Introduction Weight of the ice caused parts of Canada to sink > 300m Power of these giants shaped Canada’s landscape as we know it today Stripped the Canadian shield of topsoil Plucked enormous boulders and transported them 1000snds of km Dredged out new lake bottoms Rerouted rivers Gouged, scraped and polished exposed rock Created rolling plains of deep, fertile soil, ridges and 1000snds of lakes

Glaciation Ice sheets have covered much of Canada several times over the last 2 million years 15,000 years ago Canada and much of North America was covered in ice up to 4km thick!

Why Does Glaciation Happen? During the last Ice Age, glaciers advanced and retreated at least 4 times Why? No certain answers only theories Change in tilt of earth’s axis (41,000 yrs) Change of earth’s orbit (100,000 yrs) Change in heat output from the sun (26,000 yrs)

How Does a Glacier Form? Begins when the earth’s climate cools Winter snow fall greater then summer melt 1000snds of years snow accumulates (zone of accumulation) Becomes hundreds to thousands of m thick

Tremendous weight of snow turns bottom layer to ice Solid ice acting like a very thick liquid begins to flow outward from zone of accumulation

Alpine Glaciers Alpine Glaciers, glaciers move down mountains under force of gravity

Amounts to a few cm per day Sharpen the upper portions of mountains (fig.2-20) As they move down valleys scrape away valley walls creating U-shaped valleys (fig. 2-20)

Piedmont Glacier

Alpine Glacial Features

Continental Glaciers Occupy greater areas of land Last Continental Glacier covered 8 million square kilometers of N.A. and in some areas was up to 4 km thick

Continental Glacier Today

Continental glaciers give the landscape a smoother appearance by eroding high points and filling in lower areas with eroded material

Glaciation in Canada Glaciers move like a conveyor belt. The top moves faster than the bottom – resulting in the enormous amount of debris called till being picked up and moved along the top and deposited at the front / side of a glacier. Depositional Features Erosional Features

Sub-glacial Features

Striations

Striations?

Drumlin

Esker

Erratics on Esker

Kettle Lakes