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31 Cards in this Set
- Front
- Back
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What can be Done to Prevent Mass Movements?
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Revegetation,Regrading/terracing an oversteepened slope,Reducing subsurface water, build safety structures, controlled blasting of unstable slopes
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Rockfalls/Debris Falls
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Occur when a large mass of rock or debris free falls off of a cliff
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Debris Flows
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A quick-moving slurry of mud, sand, pebble, and boulder-sized fragments moving down a non-vertical slope
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Lahars
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- Mudflows formed when volcanic ash mixes with snow/ice found on the side of volcanoes - Flow like wet concrete - Can increase in speed and size as it gathers water and debris flowing downhill |
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Mudflows
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- A quick-moving slurry of mud - Speed of flow is determined by: - Angle of slope = higher slope, higher velocity - Water saturation = greater saturation - common in tropical areas |
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Slumps
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- Slow mass movement of regolith as coherent blocks - 4 parts: - Head scarp - Failure surface - Slump mass - Toe of slump |
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Solifluction
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- Intense creep that occurs in polar and high-elevation regions - Water cannot drain into the frozen permafrost below – results in ground being soggy, weak, and flows downhill in sheets |
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Creep
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- Slow, downhill movement of regolith due to seasonal expansion and contraction of regolith - Can be identified by tilting of landscape features |
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Mass Wasting
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- The downslope motion of rock, regolith (soil, sediment, and debris), snow, and ice - aka landslide - Driven by gravity acting on any sloping surface |
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Downslope force =
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gravity
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Resisting force =
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material properties that act against gravity
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Angle of Repose
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The steepest slope in which grains can pile up without collapsing
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Deserts
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Regions that are so arid (dry) that they have no permanent streams and only 15% vegetation coverage
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Where are most deserts located?
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Centered around the Tropics of Cancer and Capricorn
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Warm, wet air rises at the equator = lots of rain =
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tropical rainforests
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Dry air descends at 30°= no rain =
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hot deserts
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Air rises in polar regions = little precipitation =
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cold deserts
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What kind of weathering most affects deserts: physical or chemical?
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Physical
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Weathering by Wind
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Deserts have little vegetation = wind erosion important
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Weathering by Water
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- Lack of vegetation also greatly increases the effects of any rainfall a desert receives - Flash floods common, carve canyons |
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Chemical Weathering – Desert Varnish
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- A dark, rusty brown coating of iron oxide, manganese oxide, and clay that coats rocks in the desert - formed by wind blown dust settling on rocks - can't exist in humid areas - takes a long time |
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Type of dune that forms is based on three variables:
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Sand supply, Wind Strength, Vegetation
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Barchans/Parabolic Dunes
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- Crescent shaped dunes - Form in areas where sand is relatively scarce - Wind blows from one direction |
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Barchans
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tips (horns) point in the direction wind is blowing
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Parabolic
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horns point in the direction the wind came from (upwind direction)
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Transverse/Longitudinal Dunes
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- Dunes shaped like long, linear waves - Wind direction and strength determines orientation of the dunes |
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Transverse
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- lots of sand, moderate winds - Dunes form perpendicular to the wind direction |
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Longitudinal
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- abundant sand, strong steady winds - Dunes form parallel/oblique to the wind direction - Wind comes from two directions to pile up sand in ridges |
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Star Dunes
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- If wind direction changes regularly, barchans will turn into star dunes - Causes sand to stack up in the center, with horns extending out in several directions |
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Desertification
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The process of transforming non-desert areas to desert
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