Chapter - 8

1. Chapter - 8 Section – 8.3 Glaciers

2. Objectives Explain how glaciers form. Compare and contrast the conditions that produce valley glaciers with those that produce continental glaciers. Describe how glaciers modify landscapes. Recognize glacial features.

3. Glaciers modify landscapes by eroding and depositing rocks. Review Vocabulary latitude: distance in degrees north and south of the equator

4. New Vocabulary Glacier Valley Glacier Continental Glacier Cirque Moraine Outwash Plain Drumlin Esker Kame Kettle

5. Moving Masses of Ice A large, moving mass of ice is called a glacier. Glaciers form near Earth’s poles and in mountainous areas at high elevations. They cover about 10 percent of Earth’s surface.

6. Moving Masses of Ice Glaciers that form in valleys in high, mountainous areas are called valley glaciers. As valley glaciers flow downslope, they carve V-shaped stream valleys into U-shaped glacial valleys. Valley glaciers

8. Section 8.3 Moving Masses of Ice Glaciers Glaciers that cover broad, continent-sized areas are called continental glaciers. These glaciers form in cold climates where snow accumulates over many years. Continental glaciers

10. Moving Masses of Ice Glacial movement Both valley glaciers and continental glaciers move outward when snow gathers at the zone of accumulation, a location in which more snow falls than melts, evaporates, or sublimates.

11. Glacial Erosion At the high elevations where snow accumulates, valley glaciers scoop out deep depressions, called cirques.

12. Glacial Erosion When there are glaciers on three or more sides of a mountaintop, the carving action creates a steep, pyramid-shaped peak, called a horn.

13. Glacial Erosion Hanging valleys are formed by valley glaciers when tributary glaciers converge with the primary glaciers and later retreat. A valley is left hanging high above the primary valley floor.

14. Glacial Deposition Glacial till is the unsorted rock, gravel, sand, and clay that glaciers carry embedded in their ice and on their tops, sides, and front edges. Glaciers deposit unsorted ridges of till called moraines when the glacier retreats.

15. Glacial Deposition Outwash When the farthest ends of a glacier melt, meltwater floods the valley below. Outwash is the gravel, sand, and fine silt sediment that is deposited by meltwater carried away from the glacier.

16. Glacial Deposition Drumlins, eskers, and kames Continental glaciers that move over older moraines form the material into elongated landforms called drumlins.

17. Glacial Deposition Drumlins, eskers, and kames Streams flowing under melting glaciers leave long, winding ridges of layered sediments called eskers.

18. Glacial Deposition • A kame is a mound of layered sediment deposited at the retreating glacier face and is conical in shape.

19. Glacial Deposition Glacial lakes Kettles, or kettle lakes, form when water from runoff or precipitation fills a hole that formed when a large block of ice broke off a continental glacier and melted.

20. SUMMARY Glaciers modify landscapes by eroding and depositing rocks. Glaciers are large moving masses of ice that form near Earth’s poles and in mountain areas. Glaciers can be classified as valley glaciers and continental glaciers. Features formed by glaciers include U – shaped valleys, hanging valleys, moraines, drumlins, and kettles.