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Wind and Wave Erosion. …and a teeny little bit about mass movement. What is EROSION?. The removal and transport of materials by natural agents such as wind , water and ice. WIND EROSION. Sediment Sizes. Sand A sediment size…not a composition 2mm 0.06mm Gritty feel - PowerPoint PPT Presentation
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Wind and Wind and Wave ErosionWave Erosion
……and a teeny little bit about and a teeny little bit about mass movementmass movement
What is EROSION?What is EROSION?The removal and transport of materials The removal and transport of materials
by natural agents such as wind, by natural agents such as wind, water and ice.water and ice.
WIND EROSIONWIND EROSION
Sediment Sediment SizesSizes
SandSand A sediment size…not A sediment size…not
a compositiona composition 2mm 2mm 0.06mm 0.06mm Gritty feelGritty feel Can be composed of Can be composed of
anythinganything!! Not very cohesiveNot very cohesive
Sediment SizesSediment Sizes SiltSilt Smaller than Smaller than
sandsand 0.06 mm 0.06 mm
0.003mm0.003mm Fine like powder Fine like powder
Sediment SizesSediment Sizes ClayClay < 0.003 mm < 0.003 mm Smallest Smallest
sediment sizesediment size Very cohesiveVery cohesive
DeflationDeflation Most Most
common common form of wind form of wind erosionerosion
The removal The removal and and transport of transport of siltsilt
Wind ErosionWind Erosion
Dust Bowl
Kansas (1996)
Deflation and Deflation and desert desert pavementpavement
During this processDuring this process• wind removes the wind removes the top layer of fine, top layer of fine, dry rock/soildry rock/soil•fragments too fragments too large for the wind large for the wind to carry are left to carry are left behindbehind•These remaining These remaining fragments form a fragments form a surface of closely surface of closely packed rocks called packed rocks called desert pavementdesert pavement..
Wind ErosionWind Erosion Saltation- bouncing of Saltation- bouncing of
sand grains (wind lifting sand grains (wind lifting then dropping)then dropping)
http://www.nps.gov/grsa/resources/saltation.htmhttp://www.nps.gov/grsa/resources/saltation.htm
WAVE EROSIONWAVE EROSION
What causes waves?What causes waves?
Why do waves “break”?Why do waves “break”? Waves approach shoreline smoothly Waves approach shoreline smoothly
until they reach shallow water.until they reach shallow water. As waves scrapes the bottom, the As waves scrapes the bottom, the
lower part slows down and the upper lower part slows down and the upper part moves ahead…part moves ahead…
The crest falls over and breaks onto The crest falls over and breaks onto the surfthe surf
Longshore driftLongshore drift Water and sediment are transported in a zig-Water and sediment are transported in a zig-
zag pattern as longshore currents and waves zag pattern as longshore currents and waves approach the shoreline at an angle. approach the shoreline at an angle.
This zig-zag pattern is the mechanism for This zig-zag pattern is the mechanism for sediment transport as the sediment transport as the swashswash is is immediately followed by the immediately followed by the backwashbackwash to the to the ocean. ocean.
This energy created from the breaking waves This energy created from the breaking waves allows for weak currents to carry large allows for weak currents to carry large amounts of coarse-grained sediment down the amounts of coarse-grained sediment down the shoreline.shoreline.
Current + wave motion= Current + wave motion= longshore driftlongshore drift
Another look at it…Another look at it…
One more look…One more look…
Carefully examine the photo. Carefully examine the photo. Which direction is the long shore Which direction is the long shore
current coming from?current coming from?
Answer: Answer: WestWest
Longshorecurrent
Mass Movement Mass Movement (aka Mass (aka Mass Wasting)Wasting)
landslide
rockfall
creep
creepslump
mudslide
What is MASS MOVEMENT?What is MASS MOVEMENT?The term refers to downward transportation of The term refers to downward transportation of
weathered materials by gravityweathered materials by gravity
slow rapidCreep-imperceptibly slow (trees, fences)
Rockfall-
Solifluction-dependent upon cycles of freezing (similar to basal slip
Landslide-masses of loose rock/sediment
Mudflow-dry, mountainous regions with sudden, heavy rain; also volcanic activity (lahars)Slump-loose soil slips downslope as one “piece”
Triggers of Mass MovementsTriggers of Mass Movements Heavy rainHeavy rain Spring ThawsSpring Thaws Volcanic EruptionsVolcanic Eruptions EarthquakesEarthquakes
MOST COMMON?...heavy rainsMOST COMMON?...heavy rains