Chapter 12 Lesson 3, "Erosion Caused by Glaciers"

Materials:

• Worksheet, "Erosion Caused by Glaciers"

Objective:

• Students will define two types of glaciers.
• Students will explain how glaciers erode the land.
• Students will describe features caused by glaciers.

Anticipatory Set:* Show the students a picture of an Alaskan glacier. Ask what it is made out of? If it is made out of ice and snow how come it is so black? View the animation of glacial movement at: http://www.wwnorton.com/earth/egeo/flash/18_1.swf The glaciers advance during the winter and retreat during the summer. Animation 1, Animation 2.

Teacher Input:*

As snow piles up it put pressure on the snow beneath until it turns into solid ice. Glaciers do not have a size limit they just have to be an area that is snow covered all year long. There are two types of glaciers, Alpine glaciers and Continental glaciers. What causes glaciers to move? Glaciers can move huge boulders because of their great size. When the boulders freeze to the ice and the ice pushes them down the hill they act like huge pieces of sandpaper carving a cirque in the valley. As the glaciers carve the cirques they leave huge horns sticking up in the sky at the top of where the cirques start. As a glacier melts it drops the sediments that it has been carrying down the mountain or hill. It may then retreat back up the mountain. It may leave a pile of rocks called a moraine. Here is a moraine in an Iowa farm field.

Continental Glaciers: Discuss that the earth has faced periods of being covered with ice over much of its surface. For instances Alaska has been connected to Asia several times throughout the history of the word. Here is how. This is caused by several factors. Show the students the animation at: http://www.wwnorton.com/earth/egeo/flash/18_2.swf Continental glaciers are very thick and can contain ice that fell as snow thousands of years in the past. These glaciers can move boulders the size of houses hundreds of miles. In fact most of the good farm ground of Iowa was carried there from Canada during the last ice age. Most continental glaciers are now found on Greenland or Antarctica. Since continental glaciers leave marks on the soil and leave huge moraines as they retreat we know that they once covered most of the upper midwest and almost all of Canada. These glaciers are responsible for many of the lakes across Interior Alaska, Northern Minnesota and Wisconsin and the great Lakes. 1,2,3,4,5. As the glaciers retreated they dropped huge chunks of ice that filled the lakes with water and left Moraines that acted as dams. The Glaciers carved the great lakes, the finger Lakes in New York, and Lake Winnipeg in Canada.

Guided Practice:* Students will complete the Questions on page 299 as a group.

Independent Practice:* Students will complete the worksheet, "Erosion Caused by Glaciers"

Check for Understanding:* Students will take a quiz on Lesson 3, "Erosion Caused by Glaciers"

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).

Alaska Content Standards Addressed in this lesson:

• SCI A-1 Students will understand models describing the nature of molecules, atoms, and sub-atomic particles and the relation of the models to the structure and behavior of matter (Structure of Matter);
• SCI A-4 Students will understand observable natural events such as tides, weather, seasons, and moon phases in terms of the structure and motion of the earth (Earth);
• SCI A-5 Students will understand the strength and effects of forces of nature, including gravity and electromagnetic radiation (Forces of Nature);
• SCI A-7 Students will understand how the earth changes because of plate tectonics, earthquakes, volcanoes, erosion and deposition, and living things (Processes that Shape the Earth);

• SCI A-15 Students will use science to understand and describe the local environment (Local Knowledge); and: