Erosion, Deposition Notebook.notebook 1 December 05, 2012 Erosion and Deposition • Erosion • Sediment • natural forces move rock/soil from one place to another. • gravity, water, wind, glaciers, waves are causes • material moved by erosion • Deposition • when erosion lays down sediments • works with weathering & erosion • involved in wear down and build up of Earth’s surface • never ending cycle Water Erosion • Runoff & Erosion • Runoff • major agent of erosion: moving water • all remaining water on Earth’s surface • may cause sheet erosion (thin layer over land) •
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Erosion, Deposition Notebook.notebook
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December 05, 2012
Erosion and Deposition
• Erosion
• Sediment
• natural forces move rock/soil from one place to another.• gravity, water, wind, glaciers, waves are causes
• material moved by erosion
• Deposition • when erosion lays down sediments• works with weathering & erosion• involved in wear down and build up of Earth’s surface• never ending cycle
Water Erosion• Runoff & Erosion
• Runoff
• major agent of erosion: moving water
• all remaining water on Earth’s surface• may cause sheet erosion (thin layer over land)•
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• Rills
• Gullies
• tiny grooves in the soil
• large groove, or channel, in soil that carries runoff• only flow after it rains• may dry up
• Streams
• Rivers
• channel where water constantly flows down a slope• rarely dries up• also called creeks or brooks
• a large stream
• Amount of runoff
• depends on 5 factors:• 1. amount of rain in an area• 2. vegetation: grasses, shrubs, trees reduce runoff• 3. type of soil• 4. shape of the land: steep land has more runoff than flatter• 5. how people use the land• more runoff = more erosion
• River Systems
• Tributary
• Drainage Basin
• stream that flows into a larger stream• ex. small creek that flows into a large river is a tributary to that river
• land area where a river and its tributaries collect water
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• Divide
• Erosion by Rivers
• high ground between two drainage basins• ex. Continental Divide
• occurs when river meets an area of rock that is hard & erodes slowly
• Flood plains
• Meanders
• Oxbow lake
• flat, wide area of land along a river
• looplike bend in a river (snakelike)
• meander that has been cut off from a river (ushape)• may form when a river floods
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• Deposits by Rivers
• Alluvial Fan
• deposition creates: alluvial fans & deltas• can also add soil to a river’s flood plain
• wide, sloping deposit of sediment formed where a stream leaves a mountain range • shaped like a fan
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• Delta • landform made of sediment deposited where a river flows into an ocean or lake
• Groundwater Erosion & Deposition
• Groundwater
• water soaks into ground when it rains
• underground water• affects the shape of the land• causes erosion through chemical weathering• combines with carbon dioxide to form a weak acid = carbonic acid• weathers limestone• forms deposits from roof/floor of caves
• Stalactite
• Stalagmite
• Karst Topography
• deposit on roof of cave
• coneshaped deposit on floor of cave
• landscape where limestone is near the surface• characterized by caverns, sinkholes, and valleys
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Glaciers• Glacier • large mass of ice that
moves slowly over land• two types: valley (alpine) and continental
• Valley/Alpine Glacier
• Continental Glacier
• long, narrow• forms when snow/ice build up high in mountain valley• usually move down valleys cut by rivers
• covers much of a continent or large island• much larger than valley• covers 10% of Earth’s land• Antarctica & Greenland
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• Ice Ages
• continental glaciers covered large parts of Earth’s surface• last ice age lasted 70,000 years and ended 10,000 years ago
• How glaciers form & move
• only form in area where more snow falls than melts• snow builds year after year• pressure on bottom layers turns snow into ice• valley g. flow a few cm to m each day• continental flow in all directions
• Glacial Erosion
• Plucking
• two processes: plucking and abrasion
• as glacier flows, it picks up rocks• weight of ice breaks rock• carries rocks as it moves
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• Abrasion
• Deposition
• gouges, scratches bedrock as glacier drags rocks
• glacier melts, deposits sediment eroded from land• creates landforms
• Till
• Moraine
• deposits directly on surface• many different sized particles
• ridge formed when till is deposited at edge of glacier• ex. Long Island in New York
• Kettle • small depression that forms when ice is left in till• ice melts, kettle remains• often fills with water forming ponds/lakes• ex. the Great Lakes
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Waves• How waves form • waves get energy from blowing
wind• energy causes water particles to move up and down• water particles don’t move forward• only form of the wave moves• as waves approach shore, it drags on the bottom• friction causes waves to slow
• Erosion by Waves
• major erosion force along coasts • erode land by impact• large waves hit with great force• breaks apart rock• also erode by abrasion• sediment picked up by wave• wears rock like sandpaper• energy of wave depends on headlandpart of shore that sticks outharder rock; resists waves
• Landforms • waves hit same area over and over• erodes base of land along steep coasts• places of soft rock form sea caves• also forms sea arches; pillar of rock above water
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• Deposits • waves shape coast thru erosion & deposition• as waves slow, they drop sediment• similar to river deposition• forms beaches
• Beach • area of wavewashed sediment along coast• usually sand• comes from rivers that flow into ocean• some are coral/shells piled up
• Longshore Drift
• Spit
• movement of sediment caused by waves hitting shore at angles• forms a spit
• beach that projects like a finger into water
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WindHow Wind Causes Erosion
• weakest agent of erosion• effective in deserts
• Deflation • process by which wind removes surface materials• main way wind causes erosion• stronger the wind, larger the particles that can be picked up• doesn’t usually greatly affect land• creates areas of rock fragment called desert pavement• produces bowlshaped hollows called blowouts• abrasion polishes rock
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• Deposits from wind erosion
• Sand Dunes
• Loess
• forms: sand dunes & loess deposits
• deposit of windblown sand• different shapes & sizes• can move over time
• fine, winddeposited sediment• helps to form fertile soil
• Gravity
• Mass Movement • caused by gravity• different types:
*Landslides• *Mudslides• *Slump• *Creep
• Force that moves rock downhill.
• Landslides
• Mudflow
• rock/soil slide quickly down a slope
• rapid downhill movement of water, rock/soil• occurs after heavy rains in a dry area
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• Slump
• Creep
• mass of rock/soil slips down a slope• occurs when water soaks the base of a mass rich in clay
• slow downhill movement of rock/soil• often results from freezing/thawing