Glaciers

chapter 17 Holt

• 1 Glaciers: Moving Ice• 1. A glacier is a large mass of moving ice formed by

the compaction of snow.• 2. The two main types of glaciers are alpine glaciers

and continental glaciers.• 3. Glaciers move by basal slip and by internal plastic

flow.• 4. Three features of glaciers are crevasses, ice

shelves, and icebergs.• glacier, 419• alpine glacier, 420• continental glacier, 420• basal slip, 421• internal plastic flow, 421• crevasse, 422

• 2 Glacial Erosion and Deposition• 5. Glaciers create land features by eroding the land and by depositing

rock and sediment.• 6. Glaciers erode the valleys through which they flow and produce

characteristic landforms such as cirques, arêtes, horns, hanging valleys, and roches moutonneés.

• 7. When glaciers melt, they deposit sediments called glacial drift.• 8. Glacial deposits may form erratics, kettles, eskers, drumlins, and

moraines.• 9. Glaciers may form lake basins by eroding the land or by depositing

sediments.

• cirque, 424• arête, 424• horn, 424• erratic, 426• glacial drift, 426• till, 426• moraine, 427• kettle, 428• esker, 428

• 3 Ice Ages• 10. An ice age occurs when a long period of climatic

cooling causes continental glaciers to over large areas of Earth’s surface.

• 11. During an ice age, cooler glacial periods alternate with warmer interglacial periods.

• 12. The Milankovitch theory suggests that ice ages are caused by changes in the amount of solar energy Earth receives. These changes are caused by regular changes in the eccentricity of Earth’s orbit, the tilt of Earth’s axis, and precession.

• 13. Variations in solar activity, volcanic activity and plate tectonics also affect climate

• Ice age, 431• Milankovitch theory, 433