1. Erosion by Glaciers

2. A glacier is Any large mass of ice that moves slowly over land Think of it as a moving river of ice and snow

3. This is a glacier. Actually, it’s several glaciers coming together to form a larger one. The glaciers are hundreds of feet thick. They have enormous mass. They flow downhill due to the FORCE OF GRAVITY.

4. Glaciers form in areas where: The temperature is close to or below freezing most of the year. The temperature is close to or below freezing most of the year. More snow falls than melts More snow falls than melts Snow continues to fall on top of snow that is already on the ground, creating a layer of ice at the bottom.Snow continues to fall on top of snow that is already on the ground, creating a layer of ice at the bottom.

5. What are 2 types of glaciers? Valley Glaciers Valley Glaciers Continental Glaciers Continental Glaciers

6. Continental & Valley Glaciers Similarities Large masses of ice Large masses of ice Move slowly on land Move slowly on land Shape the land Shape the land

7. Valley Glaciers Def’n: Def’n: A long narrow glacier that forms when snow and ice builds up in a mountain valley Where are they located today? Held in by sides of mountains. Where were they located in the past? U-shaped valleys show where Valley glaciers once slid down slowly from a mountain. U-shaped valleys show where Valley glaciers once slid down slowly from a mountain.

11. Continental Glaciers Def’n: Def’n: A glacier that covers much of a continent Where are these located today? Cover 10% of Earth Greenland & Antarctica Where were they located in the past? Ice Ages – when large parts of Earth were covered with Continental glaciers Ice Ages – when large parts of Earth were covered with Continental glaciers

12. How fast do glaciers move? From a few cm to 3000 cm per day From a few cm to 3000 cm per day

14. Ice Ages An Ice Age is a period of very cold temperatures. An Ice Age is a period of very cold temperatures. This causes glaciers to grow and spread.This causes glaciers to grow and spread. The last Ice Age on Earth ended about 8,000 to 15,000 years ago. The last Ice Age on Earth ended about 8,000 to 15,000 years ago. During the last Ice Age, the sheet of ice around the North Pole expanded to eventually cover most of North America. During the last Ice Age, the sheet of ice around the North Pole expanded to eventually cover most of North America.

17. Cool Fact! Antarctica has the largest continental ice sheet in the world: 1 and a half times the size of the U.S. and in some places 4,000 meters deep! Antarctica has the largest continental ice sheet in the world: 1 and a half times the size of the U.S. and in some places 4,000 meters deep!

18. Cool Fact! If Greenland and Antarctica ice sheets were to melt, the sea level would rise to 60 meters! If Greenland and Antarctica ice sheets were to melt, the sea level would rise to 60 meters!

19. Glaciers are an endangered species. This is the Muir glacier in Glacier Bay, Alaska photographed in 2007.

20. The Muir Glacier is retreating rapidly. Ice is melting faster than new ice can replace it. The arrows show where the glacier was just a few years ago. As it melts it exposes rock that appears lighter because it hasn’t had time to weather.

21. These views show how the Muir Glacier has changed in just over half a century. In that time it has retreated over 20 km and it continues to get smaller every year. People may debate the causes of global warming but the evidence is clear. The Earth IS warming.

22. How are glaciers different from icebergs? An Iceberg a large piece of a glacier that has broken off and floated away after a glacier reached the ocean. An Iceberg a large piece of a glacier that has broken off and floated away after a glacier reached the ocean. Large amount of sediment may be frozen in an iceberg Large amount of sediment may be frozen in an iceberg As it melts, the sediments sink to the bottom. As it melts, the sediments sink to the bottom.

25. Did you know?!? Only a small part of the iceberg is visible from above the water’s surface Only a small part of the iceberg is visible from above the water’s surface Approximately 90% is below the water. Approximately 90% is below the water.

27. How do glaciers shape the land? Glaciers move due to the force of gravity.

28. Abrasion Gravel and pieces of rock are frozen into the ice at the bottom and sides of a glacier. Gravel and pieces of rock are frozen into the ice at the bottom and sides of a glacier. As a glacier moves, small pieces of bedrock are scraped away. As a glacier moves, small pieces of bedrock are scraped away.

29. Plucking The process by which a glacier picks up rocks as it flows across the land. The process by which a glacier picks up rocks as it flows across the land.

31. U-Shaped Valleys As a glacier scrapes away the floor and sides of a valley, it becomes U- shaped. As a glacier scrapes away the floor and sides of a valley, it becomes U- shaped. Sometimes small side glaciers flow into a main glacier  When the side glaciers melt, they leave small glacier valleys, called hanging valleys. Sometimes small side glaciers flow into a main glacier  When the side glaciers melt, they leave small glacier valleys, called hanging valleys.

34. Which of these was formed by a glacier? Which by running water?

35. Till Deposits of sediments left behind as a glacier melts (clay, silt, sand, gravel, boulders) Deposits of sediments left behind as a glacier melts (clay, silt, sand, gravel, boulders)

36. Erratics A boulder left behind by a retreating glacier. A boulder left behind by a retreating glacier.

37. Did you know?!? New York City has many erratics in Central Park! New York City has many erratics in Central Park!

38. Brainpop on Glaciers and Ice Ages Brainpop on Glaciers and Ice Ages http://www.brainpop.com/science/eart hsystem/glaciers/ http://www.brainpop.com/science/eart hsystem/glaciers/