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EROSIONEROSIONEROSIONEROSION

the transport of weathered

material by wind, water, ice

or gravity

Transporting Systems of Erosion

• Erosional systems have several parts:

– An agent of erosion (water, wind, or ice)

– The sediment being moved

– A driving force (usually gravity or the sun)

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Erosion by Water

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Running Water Erosion and Streams

• Streams carry sediment in different ways:

– Dissolved minerals are carried in solution.

– Small solids like clay are carried insuspension.

– Large solids (pebbles) are carried by rolling, sliding or bouncing along the bottom [saltation]

animation

V-shaped valley

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Wave and Current Erosion

• Longshore current- flow of water that can carry large amounts of sediments parallel to the shore, dumping them downstream

http://highered.mcgraw-

hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/0072826967/30425/14_09.swf

http://www.uky.edu/AS/Geology/howell/goodies/elearning/module14swf.swf

Ocean City

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Ocean City

Ocean City

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Ocean City

Barrier Islands

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Wind Erosion

• Deflation- winds blow away small, loose

sediments in an area lowering the land

surface

• Sandblasting (abrasion)- when winds

blow sand or silt grains against rocks and

other objects, eroding them

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Which image below shows how the cobble above will be shaped after many years of sandblasting?

Glacier

a large mass of ice & snow that exists

year-round and moves under the influence

of gravity

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Glacial Movement

Gravity pulls the snow downslope

• Material near the top & center moves quickly

• Material near the bottom & sides moves slowly due to friction

• The material in the glacier ALWAYS moves downhill, even if the glacier is melting away

Glacial Erosion

• Plucking: when the glacier ‘plucks’ pieces

of rock out of the landscape, leaving a

hole & dumping the boulder elsewhere

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Glacial Erosion

• Striations: scratches made by pieces of

sand dragged along the bottom & sides of

a glacier

• Grooves:

deeper

scratches

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Glacial Erosion

• Erratics-large sediments

transported over

many miles not

matching the

underlying bedrock

http://www.wwnorton.com/college/geo/earth/flash/22_1.swf

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U-shaped valley

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Gravity

Mass Movement: the downward transport of weathered material by gravity

FAST! OR

SLOOOW

FAST

Earthflow/Mudflow

http://stevekluge.com/geoscience/images/landslide.wmv

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FAST

Rock Fall

Talus

SLOOOW

Mass MovementCreep

Slump

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CreepSlow, imperceptible movement

of soil downslope

causes trees to curve up toward the light

Slump

when blocks of land

tilt & slide down along a curved

surface

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Sediment Features and Erosional Agents

Agent of Erosion Shape of sediment

Running water Smooth and round; Sorted

Wind Round and pitted; Sorted

Glaciers (Ice) Semi-rounded and scratched; Unsorted

Gravity Sharp and angular; Unsorted

Agents of Erosion