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18 Cards in this Set
- Front
- Back
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Deserts
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Cover extensive areas and are growing
20% of land is desert 15% is semi arid lack of rainfall is key |
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Top Largest Deserts
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Antarctica 14 million km2
Sahara 9million greenland 2mil Gobi Desert 1.125 mil |
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Distribution of Deserts
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Found in certain Latitudes
some in Polar regions (cold air can't hold moisture well) only 20% of desert areas are covered in sand |
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Weathering in Deserts
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Little water = little chemical weathering
slow iron oxides |
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Desert Erosion
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Rare but no vegetation to constrain it
arroyo - dried up stream bed |
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Wind Erosion
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Wind can only move relatively small particles
- wind has low density and viscosity - particles > .06 mm (sand) hard to erode 200-500million tons of dust are transported to the atlantic |
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Deflation
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The lifting and removal of fine, dry particles of silt, soil, and sand by the wind.
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Pavements
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desert surface that is covered with closely packed, interlocking angular or rounded rock fragments of pebble and cobble size.
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Ventifacts
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rocks that have been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals.
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Alluvial Fans
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is a fan-shaped or cone-shaped deposit of gravel, sand, and smaller materials. Deposited from streams
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Playa lakes
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Round hollows in the ground, usually filled with water (lake) but not deep and will more than likely evaporate. formed by wind/ are sinking holes
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Inselberg
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"mountain” isolated hill that stands above well-developed plains and appears not unlike an island rising from the sea
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arches
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Formed from localized erosion
national park in utah include over 2000 arches |
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Dunes
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Wind deposits of sand, initiated by surface irregularities that disrupt wind flow
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saltation
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particle (sand) transported by air and deposited back later on
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5 Different types of Dunes
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Barchan Dunes - U shaped/cone dune
Transverse Dunes - Elevated horizontal layers of sand Linear Dunes - relatively straight striated dunes Star Dunes - Wind direction varies, dunes irregular Parabolic Dune - U or V shaped dunes |
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Desertification
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Process of an area becoming a desert
sahara expanding south about 30miles/year 1 billion people in at-risk areas |
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Cause & Prevention of Desertification
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Causes:
- Tectonics - Climate - humans Prevention: - Prevent overgrazing - plant more vegetation - cut down fewer trees - conserve water |
