Erosion

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Erosion and Deposition
Erosion
 Moving sediment from one place to another
Deposition
 Setting sediment down
4 Major Agents of Erosion
 All will carry sediments if their energy of motion is great enough and all
will deposit sediments when the energy decreases
Gravity
 Mass movement - the movement of loosely consolidated fragments
down a slope
 Rapid mass movements
o Rockfall
o Landslide
o Mudflow
o Slump
 Slow mass movements
o Solifluction
o Creep
Running Water
 Most active erosive agent
 Saltation - short hops of rock grains along the bottom of a stream
channel
 Suspended - rock particles in the water column
o Faster rivers carry larger particles
 Carves out stream banks and bedrock
 Breaks up and rounds out grains (water abrasion)
 Leave thick deposits at the mouth of rivers (deltas) or the bottom of
mountains (alluvial fan)
Glaciers
 Masses of moving snow and ice (up to a mile thick!) scratch, break up,
and crush rock into rock flour (Loess)
 Cut out large U-shaped valleys, peaks & ridges, and create lakes
 Leave behind huge amounts of sediment
o Moraines = large hills of jumbled clay to boulder sized material
o Loess = thick, windblown, silty, fertile soil deposits
Wind
 Deflation - picks up only smallest grains
 Saltation - sand grains skip along surface
 Causes wind abrasion, makes ventifacts - rounded rocks
 Leaves behind dunes
Can be damaging (example: Dust Bowl of the 1930’s)
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