Erosional Forces

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Erosional Forces
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• Erosion
• Wearing away of surface materials by gravity,
  water, wind, or glaciers.
• Deposition- process where sediments are dropped
  by erosion agents as they lose energy.

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• Mass movement occurs as gravity moves materials
  down a slope as one large mass.
• Examples Slumping, Creeping, Rock
  Falls/Slides, Mudflows
• Steep slopes can be made safer with vegetation,
  drainage pipes, and walls of concrete or railroad
  ties.

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• Glaciers
• Large masses of ice and snow that slowly move on
  land causing erosion.
• Plucking- erosion process caused by moving
  glaciers picking up boulders, gravel, sand.
• Scour scrape the soil and bedrock.
• Grooves striations indicate the direction a
  glacier moved.

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• Glaciers deposit a mixture of different sized
  sediments (till) when they retreat.
• Moraine- a ridge, or pile, of deposit left at the
  end of a glacier.
• Outwash- material deposited in layers by the
  meltwater of a glacier, with largest
  pieces closer to the glacier..
• Eskers outwash deposit formed as
  meltwater rivers within the ice deposit sand
  gravel within their channels.

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Zone of Accumulation
Snowline
Crevasses
Zone of Wastage
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• Types of Glaciers
• Continental Glaciers-huge masses of ice and snow
  that cover large areas of land.
• Covers 10 of Earth near the poles. (Antarctica
  Greenland)
• Ice Ages - periods of widespread glaciation over
  the last 2 to 3 million yrs.
• Thicker than some mountain ranges.

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• Valley Glaciers- exist in mountain ranges.
• Cirques- bowl-shaped basins in the sides
  of mountains.
• Arête- a long ridge that forms when two
  valley glaciers erode a mountain side-by-side.
• Peaks- form when valley glaciers erode a
  mountain from several directions.
• Valleys formed by glaciers are U shaped

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• Wind
• Scatters dust or volcanic ash over thousands of
  kilometers.
• Deflation- wind removes small particles of
  loose sediment, leaving behind heavier materials.
• Abrasion- wind behaves like a sandblaster
  blowing sand grains against rocks wearing them
  down.

The
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• Windbreaks rows of trees planted to slow down
  wind in order to reduce erosion.
• Dunes mounds of sediment drifted by wind.

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Water Erosion
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• Surface Water
• Runoff
• Rainwater that doesnt soak in to the ground or
  evaporate.
• Affected by
• Amount of rainfall
• Length of time it falls
• Steepness, or slope, of the land
• Amount of vegetation

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• Rivers Streams
• River system network of groundwater
  streams that come together to form a system.
• Drainage Basin- area of land from which a stream
  or river collects runoff.
• The Mississippi River drainage basin is the
  largest in the United States

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• Young River
• Flows swiftly through a narrow valley.
• May have rapids waterfalls.
• Erodes the bottom faster than the sides.
• V shaped valleys

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• Mature Stream
• Flows smoothly through the valley.
• Erodes more on the sides.
• Forms meanders oxbow lakes.
• Carves a flat, broad valley floor called a
  floodplain.

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• Old Stream
• Flows smoothly through a floodplain it has
  carved.

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flood plain
meanders
oxbow lake
valley wall
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• Delta fan shaped area formed by sediments that
  are deposited as water empties into an ocean or
  lake.
• Alluvial Fan fan shaped area formed by
  sediments that are deposited as water empties
  from a mountain valley onto a flat open plain.

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• Groundwater
• Groundwater is water that soaks into the ground
  and collects in the pores of the underlying soil.
• Soil and rock are permeable if water can pass
  through the pore spaces. (Sandstone)
• Soil and rock are impermeable if water can not
  pass through the pore spaces. (Granite)

• Aquifer a layer of permeable rock that
  lets water move freely.
• Zone of Saturation area where all the pores are
  filled with water.
• Water Table upper surface of the zone of
  saturation.

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Aquifer
Zone of Saturation
Zone of Aeration
Water Table
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• Wells are used to pump groundwater from an
  aquifer to the surface.
• Artesian wells wells that dont require a pump
  because the water is under pressure.
• Spring free flowing water because the water
  table is so close to the surface.
• Geyser hot spring that erupts peroidically,
  shooting water steam into the air.

The the
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• Caverns are formed by Carbonic acid dissolving
  limestone rock, thereby enlarging cracks to form
  chambers.
• Stalactites Calcium carbonate deposits that hang
  from a caves ceiling.
• Stalagmites Calcium carbonate deposits that
  form on a caves floor.

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Other Features
Soda Straws
Columns
Cave Popcorn
Draperies
Cave Pearls
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• Ocean Shoreline
• Shoreline Forces
• Waves pound against pound against shores.
• Currents move sediments along the shoreline.
• Tides carry sediment out to sea bring in new
  sediment.

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• Rocky Shorelines
• Rocks cliffs
• C. Sandy Beaches
• Beaches deposits of sediments parallel to the
  shore.
• Barrier Islands fragile sand deposits that
  parallel the shore but are separated from the
  mainland.