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

• ­rivers create: valleys, waterfalls, flood plains, meanders, & oxbow lakes

• V­Shaped Valleys

• Waterfalls

• ­form when rivers erode along steep slopes

• ­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

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Attachments

Meanders, erosion, deposition animation

Animations: erosion and depositon

Coastal Erosion