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Earth Science Chapter 8 Section 3
Glaciers Earth Science Chapter 8 Section 3
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Moving Masses of Ice Glacier Large, moving mass of ice
Form near Earth’s poles and mountainous areas Extreme latitude and elevations Regions with year round temperatures of 0° C Moving Masses of Ice
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Cold temperatures keep fallen snow from completely melting
Each year new snow accumulates in snow field Thickness increases as years pass Extreme weight and pressure turn the snow into ice Moving Masses of Ice
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Valley Glaciers Form in valleys high in the mountains
Movement occurs when ice mass becomes so heavy it holds its shape and begins to flow Usually begins when accumulation is over 20 m Valley Glaciers
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Speed of valley glacier depends on slope of the valley floor and temperature of the ice
Sides and bottom move slower than the middle Movement is slow Carve U-shaped valleys Valley Glaciers
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Deep cracks in the surface of the ice
Crevasses
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Continental Glaciers Glaciers that cover broad, continent-sized areas
Form in cold climates Snow accumulates over many years Thickest at its center Weight of the center forces rest of ice out in directions Greenland and Antarctica Continental Glaciers
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Move outward when snow gathers when snow accumulates at the zone of accumulation
A location in which more snow falls than melts Valley glaciers- top of mountains Continental glaciers- center of the ice sheet Glacial Movement
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Glacial Erosion Most powerful erosional agent
Large size, weight and density Plucking- when a glacier breaks off a piece of rock The embedded rock adds to the erosional impact Glacial Erosion
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Striations and grooves on underlying rock are caused when rocks carried by the glacier “scratch” underlying rocks. Striations
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Cirques Deep depressions carved out by valley glaciers
Arête: when two cirques on opposite sides of a valley meet Sharp steep ridge Horn: when glaciers are on three or more sides of a mountain Carve steep pyramid shaped peak Cirques
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Formed when tributary glaciers converge with primary glacier and then retreat
Primary glacier so large it meets the tributary glaciers When they melt, the smaller valleys are left above the valley of the primary glacier Hanging Valley
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Till- unsorted rock, gravel and sand that glaciers carry
Moraines- the deposited till left when a glacier retreats Terminal moraines- found along retreating edge of the glacier Lateral moraines- located parallel to the glacier Glacial Deposition
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Outwash Melt water that floods the valley below the glacier
Contains gravel, sand and fine silt Sediment sorted by particle size Outwash plain- leading edge of glacier where outwash flows and deposits sediment Outwash
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Drumlins Continental glaciers that move over older moraines
Elongated landforms are created Drumlins
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Kames and Eskers Kames Eskers
Mound of layered sediment deposited at the retreating glacier face conical in shape Streams flowing under melting glaciers leave long winding ridges of layered sediments Kames and Eskers
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Glacial Lakes Blocks of ice break off a continental glacier
Surrounding area is covered by sediment When ice block melts the kettle hole fills with water Common in New England, New York and Wisconsin Glacial Lakes
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Cirque lakes form when cirques fill with water
Glacial Lakes
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Moraine-dammed lakes form when a terminal moraine blocks off the valley and the valley fills with water Great Lakes and finger lakes Glacial Lakes
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