Glaciation

media type="file" key="Glaciation.mp3" width="240" height="20" Let's get started with this video [|Glaciers]

**Activity** Go to this site on glaciers. You will be assigned one short section to summarize and present to the class. You will have 20 minutes to tackle this, but it's only a little writing.

1. In your own words, describe how glaciers form.

Did you know that ice is one of the hardest substances on earth? This seems strange when we see fragile ice crystals on window panes, or ice cubes floating in cool drinks. Yet ice had the power not only to damage the hull of the Titanic, but also to transform the shape of the land.

 The earth has experienced several ice ages. About 250 million years ago, parts of South America, Africa, India, Australia, and Antarctica were glaciated when they were part of Pangaea, the supercontinent. North America and Europe were not glaciated at this time because they were located near the equator. There is also evidence that there were several previous ice ages, including one 2 billion years ago and another 600 million years ago. For most of the earth's geologic history, however, glaciers have not covered large parts of the land. The last Ice Age began between one and two million years ago. Ice sheets covered almost all of Canada and parts of the United States, Europe, and South America during each of its glacial advances. Enormous volumes of the world's water were frozen in these ice sheets. This caused the level of the oceans to fall well below current levels.

2. Think of all the ice at the Earth's poles (North and South). You can look on a map if you like. What do you think the effect would be if it all melted?

 During the last Ice Age, glaciers advanced and retreated at least four times. Between each period of glacial activity, the climate was as warm, or warmer, than today. Why did such a cycle occur? No one is quite sure, but some theories suggest it has to do with changes in the earth's orbit around the sun as well as changes in the tilt of the earth's axis, or changes in the heat output from the sun.

 The Ice Age's last period of glacial activity began about 100 000 years ago, and ended in most parts of Canada about 6000 years ago. A period of glacial activity begins when the earth's climate cools, and the snow that falls in the winter does not completely melt in the summer. Over thousands of years, the snow gets deeper and becomes hundreds or thousands of metres thick. The tremendous weight of the snow on top causes the bottom layers to turn to ice. The most remarkable fact about a glacier, other than its tremendous size, is that it can move. Solid ice acts like a very thick liquid, and moves along or flows very slowly.

 Glaciers move in different ways, depending upon their location and the climate. In mountainous regions, alpine glaciers move down valleys from high elevations to low elevations under the force of gravity. This movement is usually only a few centimetres per day. Alpine glaciers sharpen the upper portions of the mountains and give them a rugged appearance. When they move down valleys, they scrape away the valley walls to produce broad U-shaped valleys.

 Alpine glaciers exist today in Canada in parts of the Western Cordillera and the Arctic islands. The Columbia Icefield is a mass of ice located along the British Columbia-Alberta border between Banff and Jasper National Parks. It is the largest area of ice in Canada south of the Arctic. It contains 30 glaciers covering about 300 km{2} to depths of 365 m. Waters from this icefield flow into three different oceans. Tourists from all over the world tome to our western mountains to enjoy the beauty created by glacial activity.

 Continental ice sheets, or continental glaciers, are different from alpine glaciers in that they occupy greater areas of land, and move under their own weight. During the last glacial advance, about 8 million square kilometers of North America were covered by a continental ice sheet. In some spots, this ice sheet reached a thickness of 4 km.

 Continental glaciers give the landscape a smoother appearance by eroding higher points on the land and filling in lower areas with the eroded material. Today, continental glaciers exist only in Greenland and Antarctica.

3. What area of Canada have we learned was ground down by the force of glaciers?