co: weathering and erosion lo: describe the types and causes of weathering of erosion. 1

CO: Weathering and ErosionCO: Weathering and Erosion

LO: Describe the types and causes LO: Describe the types and causes of weathering of erosion.of weathering of erosion.

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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!

WeatheringWeathering

Chemical weatheringChemical weatheringdecomposition of rocks and minerals via decomposition of rocks and minerals via chemical reactionschemical reactions at the Earth’s surface at the Earth’s surface

Physical weatheringPhysical weatheringdisintegration/disaggregation of rocks via disintegration/disaggregation of rocks via mechanical mechanical processesprocesses

1. Physical Weathering1. Physical WeatheringA.A. Ice wedging Ice wedging – –

• water penetrates into cracks, expands when it water penetrates into cracks, expands when it freezes.freezes.

• cracks grow, new cracks formcracks grow, new cracks form

Physical WeatheringPhysical Weathering

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

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

Exfoliation Weathering-formation of exfoliationdome

Spheroidal weathering in the arid SW USASpheroidal weathering in the arid SW USA

2. Chemical Weathering2. Chemical Weathering

Minerals are destroyed or altered Minerals are destroyed or altered by chemical reactionsby chemical reactionsa. Dissolutiona. Dissolution

b. Hydrolysisb. Hydrolysis

c. Oxidationc. Oxidation

ErosionErosion

Removal of weathered material from Removal of weathered material from its place of origin. its place of origin.

Eroded material is called Eroded material is called sedimentsediment.. GravityGravity is the driving force of erosion is the driving force of erosion

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ErosionErosionThere are many types of There are many types of

erosionerosionA. Mass A. Mass movement-movement- a a process that process that moves sediment moves sediment down a hilldown a hill

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Mass MovementMass MovementThere are 4 ways a mass movement may There are 4 ways a mass movement may

occuroccur1.1. Landslide-Landslide- a rapid a rapid

movement movement of large of large amounts of amounts of rock and rock and soilsoil

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Mass MovementMass Movement

2. Mudflow-2. Mudflow- a a rapid downhill rapid downhill movement of movement of a mixture of a mixture of water, rock water, rock and soiland soil

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Mass MovementMass Movement

3. Slump-3. Slump- mass of mass of rock and soil rock and soil suddenly slips down suddenly slips down a slopea slope

• This is different This is different from a landslide from a landslide because it comes because it comes down in one down in one large masslarge mass

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Mass MovementMass Movement

4. Creep-4. Creep- a very a very slow movement of slow movement of rock and soilrock and soil

• Usually creeps Usually creeps cause objects cause objects to sit at to sit at unusual anglesunusual angles

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B. Water ErosionB. Water Erosion

StreamStream- a channel along which water - a channel along which water continually flowscontinually flows

RiverRiver- a large stream usually formed from - a large stream usually formed from several streams flowing togetherseveral streams flowing together

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1. Features of Streams1. Features of Streams

a.a. Flood Plain-Flood Plain- a flat area along a stream a flat area along a stream that is entirely covered only during times that is entirely covered only during times of floodsof floods

b.b. MeanderMeander- the winding and bending of a - the winding and bending of a stream as it erodes the landstream as it erodes the land

Only older streams do thisOnly older streams do this

c.c. Oxbow Lake-Oxbow Lake- when sediment builds up, when sediment builds up, cutting off the meander from the rest of cutting off the meander from the rest of the river, causing a separate, curved lakethe river, causing a separate, curved lake

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Flood Plains:Flood Plains:Area that the river floods over 100s Area that the river floods over 100s

or 1000s of years.or 1000s of years.

Mississippi Flood plain1919

Flood PlainFlood Plain

Mississippi Flood plain

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Old Age Old Age Tigre River, ArgentinaTigre River, Argentina

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Meandering Streams and Oxbow Meandering Streams and Oxbow LakesLakes

Stream aging and deposition Meandering erosion

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Water ErosionWater Erosion

2. Fast moving 2. Fast moving rivers that are rivers that are straight and straight and narrow cut steep narrow cut steep slopes and create slopes and create a V-shaped valleya V-shaped valley

• Example- Example- Yellowstone Yellowstone canyoncanyon

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Grand CanyonGrand Canyon

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Water ErosionWater Erosion

3. Waterfall3. Waterfall- a river - a river cuts through soft cuts through soft rock faster than rock faster than hard rock hard rock • Example- Niagara Example- Niagara

FallsFalls• It is retreating ¼ It is retreating ¼

inch each year.inch each year.

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Niagara FallsNiagara Falls

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4. Groundwater Erosion4. Groundwater Erosion

Chemical erosion undergroundChemical erosion undergrounda. Makes caves and sinkholes a. Makes caves and sinkholes

1. CAVE1. CAVE- limestone erodes away, leaving - limestone erodes away, leaving behind a dry narrow passagebehind a dry narrow passage

2. SINKHOLE2. SINKHOLE- weakened limestone where the - weakened limestone where the entire portion of the ground suddenly entire portion of the ground suddenly collapsescollapses

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C. Glacial ErosionC. Glacial Erosion

1. Glaciers erode land in 2 ways1. Glaciers erode land in 2 ways• Plucking-Plucking- as a glacier flows over land it picks as a glacier flows over land it picks

up rocksup rocks• Abrasion-Abrasion- gauges and scratches in rocks as a gauges and scratches in rocks as a

glacier drags across landglacier drags across land

2.2. Causes large, bowl shaped valleys called Causes large, bowl shaped valleys called cirquescirques

3.3. Cuts U-shaped valleys in landformsCuts U-shaped valleys in landforms

4.4. May leave behind large, cold glacial lakesMay leave behind large, cold glacial lakes

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What process makes a hanging What process makes a hanging valley?valley?

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D. Wind ErosionD. Wind Erosion DeflationDeflation- wind picks up and carries away small - wind picks up and carries away small

particlesparticles• The faster the wind, the larger the particles it The faster the wind, the larger the particles it

can carrycan carry

Example- Sand dunesExample- Sand dunes

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