Erosion Deposition 12 14 15 Water Erosion Biggest

Erosion & Deposition 12 -14 -15

Water Erosion Biggest agent of erosion -sediments get rounded and polished due to abrasion. Sorting occurs. • particles can be fairly large. • deposition occurs where the water slows down. – ex. : where the river widens or where it dumps into a large body of water. • As water slows gradually, smaller and smaller particles drop out causing horizontal sorting.

As a river or streams develops, it changes in shape, width, and size Rivers and Streams • Meander- curve in a river • Tributary- smaller streams flow into larger ones. • Floodplain- area next to a river that is usually flat and • Base level- lowest point to can be flooded. which a stream can erode • Delta- area of low, flat land (mouth of river) where a river divides into • Headward erosion- smaller rivers before streams wear away rock flowing into a larger body and soil at their headof water making the stream longer

Streams • Down cutting- is vertical erosion, which deepens a stream • Side-cutting- is lateral erosion, which widens a stream • In a straight section of a stream, the fastest water is in the middle above center.

Streams • On a curve, the fastest water gets thrown to the outside and that's where erosion will happen. • The slowest water hugs the inside of the stream and that is where deposition takes place.

Cross sections of a stream • Draw cross sections For A-B, and C-D

Types of rivers • Youthful rivers- narrow V-shaped, fast water, Steep gradient, erosion is dominant • Mature rivers- lateral erosion(widens channels), meanders & floodplains develop, gradient is less steep • Old rivers- Low velocity, low gradient, oxbow lakes form

Youthful rivers

Mature rivers

Old rivers Water slows in the outside loop causing deposition. The loop gets cut off into an “Oxbow Lake” while the stream returns to a straighter course. http: //www. cleo. net. uk/resources/displayframe. php? src=309/consultants_resources/_files/meander 4. swf

Rivers from young to old youthful mature old

Gradient • Gradient- the steepness of a slope = change in field value distance • When slope is steep and flow is fast= V-shaped valley Ex: Grand Canyon • When slope is gentle and flow is slow= Ushaped valley

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Deposition • Occurs when sediments are laid down on the ground or sink to the bottom of a body of water • Final stage of the erosional process

Animations http: //www. cleo. net. uk/resources/dis playframe. php? src=309/consultants_ resources/_files/meander 4. swf http: //www. wiley. com/college/strahle r/0471480533/animations/ch 17_anim ations/animation 1. html

Glaciers • Glacier- large moving mass of ice and snow • Most powerful agent of erosion because of size, weight, and density • Will show unsorted sediments-mixed sizes • Classified into 2 groups: – Continental glaciers (form over broad, continent -sized areas) – Valley glaciers (form in high mountain regions)

Alpine Glacier (valley glaciers) Large moving streams of ice, found high in mountain found around the world.

Continental Glaciers: are large sheets of ice that cover large parts of continents. These glacier move outward from the center of accumulation.

Advancing Glacier: Glacier that has an ice front that moves forward. (more accumulation) Retreating Glacier: glacier has an ice front that moves back (more ablation) http: //www. uky. edu/AS/Geology/howell/ goodies/elearning/module 13 swf. swf

Till-unsorted sediments from glaciers

Glacial Deposition • Moraines- ridges • Outwash plainsdeposits at front of glacier (meltwatersorted and layered) • Kettle lakes- form in shallow basins scooped out by receding glacier. • Drumlins- narrow hill - shows direction of movement

esker Glacial lake drumlin moraines Kettle holes/lakes outwash Outwash plain stream

Glacial erosion • Result in accumulation of a large amount of mixed debris that becomes embedded in glacier • Parallel scratches- occurs when glaciers w/ embedded materials move over bedrock valley walls – Grooves- large scratches – Striations- small scratches

Striations How can these striations help you determine the movement of of the glacier?

Erratics- large boulders left behind from a glacier

The U-shaped Valley on the left was made by a glacier while the V-shaped valley on the right was made by running water.