glacier geo test 3

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glacier geo test 3
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glacier geo test 3
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  1. GLACIER
    • A. Large mass ice accumulates over 100-1000s years
    • B. Form from the accumalation of snow
    • 1.Snow compacted and recrystallized to form glacial ice
    • C. Most glaciers move slowly
    • D. Glaciers erode, transport, deposit large amounts of materia
    • E.Glacial action is responisible for shaping landforms
    • F. Glaciers cover approx. 10 percent of Earths surface today
  2. Types of Glaciers
    • A. VALLEY GLACIERS
    • 1. Form in mountanious areas move down stream valleys
    • 2. all continents except Australia
    • B.ICE SHEETS (continental glaciers)
    • 1. Glaciers move outward in all directions from one or more centers of accumalation
    • 2. found only in Antartica (thickness -14000 feet) and Greenland
  3. Glacial Movements
    • A. ZONE OF FRACTURE- Upper150 feet of glacier
    • B. ZONE OF FLOW
    • 1. Glacier movement occurs
    • 2.Basal Slip-glacier moves along underlying bedrock due to lubrication by meltwater
    • 3. Plastic flow-ice actually flows in this zone
  4. Glacial Budget
    • A.ZONE OF ACCUMULATION
    • 1. Snow accumulation and ice formation occur here
    • 2. Ice is added to the glacier
    • B. ZONE OF WASTAGE
    • 1. All the snow from the previous winter and glacial ice are lost
    • a. melting
    • b. Calving-pieces of glacier break off when glacier flows into a lake of ocean
    • C. GLACIAL BUDGET
    • 1. Terminus-end of valley glacier of an ice sheet
    • 2. When accumulation>wastage, terminous advances
    • 3.When wastage>accumulation, the terminus retreats
    • 4. When accumulation=wastage, terminus remains stationary
  5. Glacial Erosion
    • A. Plucking-pieces of bedrock freeze to bottom of glacier and pulled out as the glacier moves
    • B. Abrasion-
    • 1. Abrasive effect of particles transported along bottom and sides of glacier
    • 2. Glacial striations- scratches made on underlying bedrock long particles moved along bottom glacier
    • 3.Rock Flour
    • i. Pulverized rock material (silt and clay sized) created rocks grind against each other during transport
    • ii. May be picked up by wind and deposited as loess
  6. EROSIONAL FEATURES CREATED BY VALLEY GLACIERS
    • A. U-shaped glaccial trough- valley glaciers widden, deepen, straighten stream valleys
    • B. Cirques-bowl-shaped depressionas at head of glacial valley
    • C. Hanging valley-
    • 1.Smaller tributary glaciers cant erode their valleys as deeply as main glacier
    • 2. When glaciers melt, smaller valleys are left above main main valley
    • 3.Waterfalls from where water flows from hanging valleys
    • D.Aretes-knifelike ridges separate glacial valleys or cirques
    • E. Horns- pyramidlike peaks form in areas where three or more ciques surround peak
    • F. Fjords-drowned glacial valley along coasts.
  7. GLACIAL DEPOSITION
    • A.DRIFT- general term for sediment deposited by glaciers
    • 1. Till- poorly sorted glacial material deposited when glacial ice melts
    • 2. Stratified drift-glacial deposits trans and depo by meltwater
    • B.MORAINES
    • 1. Layers of till
    • 2.Lateral moraine- material trans along sides of valley by valley glacier, forms lateral moraine when deposited
    • 3. Medial Moraine-formed where two lateral moraines join in a valley glacier
    • 4. End of Moraines
    • a. Form at terminus of a valley glacier or ice sheet
    • b.Terminal end moraine- form when terminus of a glacier is stationary
    • c. Ground Moraine-layer of till deposited as glacier retreats
    • d. Recessional moraine- form when the terminus of a retreating glacier becomes stationary
    • C. VALLEY TRAINS AND OUTWASH PLAINS
    • 1.Outwash plains-stratified drift deposited in front of ice sheet
    • 2. Valley trains-stratififed drift deposited beyond terminus of valley glaciers
  8. Ice sheets
    • A.OFTEN PRODUCE ROLLING TOPOGRAPHY
    • B. FEATURES ASSOCIATED WITH RETREATING ICE SHEETS
    • 1. Drumline
    • a. symmetrical hills composed of till
    • b. Probably molded in the zone of flow
    • 2. Eskers- sinuous ridges of stratified drift deposited by meltwater flowing under the edge of glaciers
    • 3. Kettles-depressions formed when a block of ice is left being by a retreating glacier and buried in drift
    • 4.Braided streams
    • a. Meltwater flowing frm glaciers carries large load of sediment
    • b. Gravel and sand bars are deposited in the channels
    • c.When water level is low, water has to flow around the bars producing a network of channels.
    • 5. Terminal end and recessional moraines
  9. Pleistocene Epoch
    • A. Pleistocene Epoch
    • 1. 1.6 my -10,000 years
    • 2.Ice sheets covered approximately 30 percent of Earths surface
    • 3. Evidence for four glacial advances and retreats on land
    • 4. Evidence from ocean floor sediment indicates at least 20 warming/cooling cycles occured
    • B. EFFECTS OF GLACIATION
    • 1. Sea level changes
    • a. Occur when glaciers advance and retreat
    • b. Sea level was about 450 feet lower than today at times during Pleistocene
    • 2.Isostatic rebound
    • a. Crust was depressed by weight of ice sheets
    • b. When ice sheets retreated, crust slowly rebounded
    • i. Some areas are still rebounding from Pleistocene glaciation
    • 3.Some mammals grew to unusually large sizes
    • a. Mammoths, ground sloths, Irish elk, glyptodonts, etc.
    • 4.Pluvial Lakes
    • a. Climates during the Pleistocene were cooler and wetter
    • b. Permanent lakes formed in areas such as Death Valley
    • c. Great Salk Lake is a remnant of much larger lake that formed during Pleistocene

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