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Surface Processes on Earth Weathering, Erosion & Freshwater
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Weathering and Erosion
Weathering is the process of breaking down rocks at or near the Earth’s surface. Erosion is the movement of sediments from one place to another.
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Weathering Mechanical Chemical
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Mechanical Weathering
Does NOT change the rock CHEMICALLY Natural processes just eat away at (Erode) the surface
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Mechanical Weathering
FROST/ICE WEDGING: repeated thawing and freezing of water in cracks of rocks UPLIFTING: when layers of rock above are removed, the release of PRESSURE allows the rock to expands and cracks Plant growth into cracks can split open rocks EXFOLIATION: the action of EXFOLIATION allows outer rock layers to be striped away
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Chemical Weathering Occur when CHEMICAL REACTIONS take place within the rock Eroded sediments are different chemically Erosion Increases with SURFACE AREA Water, oxygen, carbon dioxide and acids can cause chemical weathering
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Chemical Weathering Hydrolysis = water. Occurs in Silicate Minerals
Oxidation = oxygen. Occurs in Iron Minerals = RUST Carbon dioxide. Combines with water to form a weak CARBONIC acid Acid Rain. Released by human activities that make pollution.
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Rate of Weathering Water-Soluble minerals weather easily (Like salt melts into salt water) Different layers weather at different rates
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Other Factors More surface area = more weathering
Topography (slopes, hills, etc) allows gravity push sediments downhill faster than on flat surfaces
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Erosion Transportation of Sediment Water Wind Glaciers
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Soils Or as some call it.. Dirt
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Soils Soil is made of Soil Texture depends on particle SIZE
Rock particles and minerals (sand, silt, clay) Humus is organic and provides PLANTS with air and water Soil Texture depends on particle SIZE
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Soil Horizons The layers of soil are called the soil horizon
TOP SOIL – Layer A: contains NUTRIENTS and minerals and is very dark SUB-SOIL- Layer B: high in clay and is usually red or yellow in color Layer C: Partially weather rock
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Life in Soil Decomposers (such as fungi and bacteria) break down ORGANIC MATERIAL Animals mix SOIL LAYERS and allow air and water to pass through it. Humus = Plants produce litter and then decay which returns nutrients to the soil.
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Soil in the U.S. Polar (Alaska) – good drainage, no horizons, permafrost Temperate (Eastern and Central U.S.) – vary greatly Grassland – fertile Forest – less fertile Desert (Western U.S.) – high in salts and little organic/living material Tropical – can become infertile due to high rainfall
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Soil Damage Loss of TOP SOIL Due to erosion Desertification
Climate Change, Overgrazing, Cutting down FORESTS
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Conservation Contour plowing CONSERVATION plowing
Fallow (allowing fields to rest) CROP rotation
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Karst Topography Differential erosion causes KARST TOPOGRAPHY.
Groundwater contains some ACID usually CARBONIC ACID Acid gets there when carbon dioxide combines with water Differential erosion causes KARST TOPOGRAPHY. Acid dissolves some types of minerals Calcites Limestone Acid leaves others Quartz Sandstones Igneous rocks
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Features of Karst Caves Sinkholes Stalactites – from above
Stalagmites – from below Disappearing rivers
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Karst Topography
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Caves
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Sink Holes
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Stalactites They hold TIGHT to the ceiling
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Stalagmites They MIGHT have fallen
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Disappearing Rivers
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Mass Movement by Gravity
The downward movement of loose sediment and weathered rock. Slide: moves as a block Flow: particles mix together Fall: falling freely
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Slow, Steady, Downhill flow of sediment
Creep Slow, Steady, Downhill flow of sediment
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Mass of sediment falls down
Slump Mass of sediment falls down
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swiftly moving mixture of mud and water
Mudflow swiftly moving mixture of mud and water
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downhill movement of saturated topsoil
Landslide downhill movement of saturated topsoil
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Landslides of snow (deep snow)
Avalanche Landslides of snow (deep snow)
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Mass Movement Caused by Wind
Mass movement from wind includes Dust Storms Dunes Formation
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Mass Movement by Glaciers
A glacier is a large moving mass of ice
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The Water Cycle
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Runoff Water moving along the surface will carry sediments.
If surface is POROUS, then water can flow into the ground. Plants slow erosion and allows more water into the ground Light rains can allow more water into the ground Soil types affect absorption
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Run Off & Porosity
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Watershed All the land that drains into a stream or river system is called the watershed. Suspension: particles carried in water Bed Load: particles pushed along by water in a stream
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Streams Stream channel: the pathway carved by a stream
Stream banks: the ground bordering the stream on either side Floods occur when streams or rivers rise over their banks. Flood plain: the broad flat area on either side of the stream banks. Meander: the bend and curves in a stream
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Streams
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Lakes and Freshwater Wetlands
Lakes are depressions in the landscape that collect and hold water. Eutrophication: the process by which lakes absorb nutrients from the soil around them. Wetlands are land areas that are covered by water for part of the year. Bogs Marshes Swamps
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Groundwater and Infiltration
Infiltration is when water on the surface flows into the ground An aquifer is the area of ground water flow through permeable rock
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Groundwater
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Groundwater Zone of Saturation – the depth to which ground water completely fills all the pores in the material. Upper boundary is the Water Table Permeability – how easily water passes through Zone of Aeration – is the area above the water table
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Groundwater Systems Springs - Natural discharges of ground water where ground water is blocked by AQUICLUDES (Clay and Shale) Hot springs usually form near residual igneous activity Geysers are explosive hot springs that erupt at regular intervals.
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Wells Wells are holes that are drilled or dug into the ground to reach the aquifer Drawdown – the difference between the water table level and the water level in the pumped well Recharge – the water filtering into the well from the ground water Artesian well – a well in a CONFINED aquifer.
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