CO: Weathering and Erosion LO: Describe the types and causes of weathering of erosion. 1

Physical breakdown and/or chemical alteration of rocks and minerals at or near the earth’s surface. Weathering Erosion Removal of weathered material from its place of origin. -eroded material is called sediment. Are they the same thing?? NO!

Weathering Chemical weathering decomposition of rocks and minerals via chemical reactions at the Earth’s surface Physical weathering disintegration/disaggregation of rocks via mechanical processes

1. Physical Weathering A. Ice wedging – water penetrates into cracks, expands when it freezes.water penetrates into cracks, expands when it freezes. cracks grow, new cracks formcracks grow, new cracks form

Physical Weathering B. Root wedging - plant roots penetrate into cracks causing them to widen.

Sheeted granite along Tioga Road near Yosemite Nat’l Park. -caused by expansion jointing

Exfoliation Weathering -formation of exfoliation dome

Spheroidal weathering in the arid SW USA

2. Chemical Weathering Minerals are destroyed or altered by chemical reactions Minerals are destroyed or altered by chemical reactions a. Dissolution b. Hydrolysis c. Oxidation

Erosion Removal of weathered material from its place of origin. Removal of weathered material from its place of origin. Eroded material is called sediment. Eroded material is called sediment. Gravity is the driving force of erosion Gravity is the driving force of erosion 11

Erosion There are many types of erosion A. Mass movement- a process that moves sediment down a hill 12

Mass Movement There are 4 ways a mass movement may occur 1. Landslide- a rapid movement of large amounts of rock and soil 13

Mass Movement 2. Mudflow- a rapid downhill movement of a mixture of water, rock and soil 14

Mass Movement 3. Slump- mass of rock and soil suddenly slips down a slope This is different from a landslide because it comes down in one large massThis is different from a landslide because it comes down in one large mass 15

Mass Movement 4. Creep- a very slow movement of rock and soil Usually creeps cause objects to sit at unusual anglesUsually creeps cause objects to sit at unusual angles 16

B. Water Erosion Stream- a channel along which water continually flows Stream- a channel along which water continually flows River- a large stream usually formed from several streams flowing together River- a large stream usually formed from several streams flowing together 17

1. Features of Streams a. Flood Plain- a flat area along a stream that is entirely covered only during times of floods b. Meander- the winding and bending of a stream as it erodes the land Only older streams do this c. Oxbow Lake- when sediment builds up, cutting off the meander from the rest of the river, causing a separate, curved lake 18

Flood Plains: Area that the river floods over 100s or 1000s of years. Mississippi Flood plain 19

Flood Plain Mississippi Flood plain Mississippi Flood plain Mississippi Flood plain Mississippi Flood plain 20

Old Age Tigre River, Argentina 21

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Meandering Streams and Oxbow Lakes Stream aging and deposition Stream aging and deposition Stream aging and deposition Stream aging and deposition Meandering erosion Meandering erosion Meandering erosion Meandering erosion 23

Water Erosion 2. Fast moving rivers that are straight and narrow cut steep slopes and create a V-shaped valley Example- Yellowstone canyonExample- Yellowstone canyon 24

Grand Canyon 25

Water Erosion 3. Waterfall- a river cuts through soft rock faster than hard rock 3. Waterfall- a river cuts through soft rock faster than hard rock Example- Niagara FallsExample- Niagara Falls It is retreating ¼ inch each year.It is retreating ¼ inch each year. 26

Niagara Falls 27

4. Groundwater Erosion Chemical erosion underground a. Makes caves and sinkholes 1. CAVE- limestone erodes away, leaving behind a dry narrow passage 2. SINKHOLE- weakened limestone where the entire portion of the ground suddenly collapses 28

C. Glacial Erosion 1. Glaciers erode land in 2 ways Plucking- as a glacier flows over land it picks up rocksPlucking- as a glacier flows over land it picks up rocks Abrasion- gauges and scratches in rocks as a glacier drags across landAbrasion- gauges and scratches in rocks as a glacier drags across land 2. Causes large, bowl shaped valleys called cirques 3. Cuts U-shaped valleys in landforms 4. May leave behind large, cold glacial lakes 29

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What process makes a hanging valley? 33

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D. Wind Erosion Deflation- wind picks up and carries away small particles Deflation- wind picks up and carries away small particles The faster the wind, the larger the particles it can carryThe faster the wind, the larger the particles it can carry Example- Sand dunes 39