Wind erosion amp Deposition What is wind Wind the horizontal flow of air It is caused by horizontal differences in pressure which result from the unequal heating of Earths surface httpwwwclasszonecombooksearthscienceterccontentvisualizationses1903es1903page01cfmchapt ID: 574880
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Slide1
WED V15
Wind erosion & DepositionSlide2
What is wind?
Wind the horizontal flow of air.
It
is caused by
horizontal differences in pressure which result from the unequal heating of Earth’s surface
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm?chapter_no=visualizationSlide3
Features caused by wind
Ripples and dunesSlide4
Windward side is gentle
Leeward side is steep
http://geology.wr.usgs.gov/parks/coast/dunes/index.htmlSlide5
For dunes & ripples to form you need…
Wind
Dry sand
Wind break (drift wood, dead bird, plant, etc.)Slide6
Dunes
http://geology.wr.usgs.gov/parks/coast/dunes/index.htmlSlide7
Dune Formation
steady supply of sand, wind, and a wind break
beaches and at the base of mountains in dry regions.
Wet sand will not blow around to form ripples and dunes
Mesquite Flats, Death Valley, CA
http://www.uoregon.edu/~millerm/sanddunes.htmlSlide8
Grasses on the dunes help stabilize the beach
http://geology.wr.usgs.gov/parks/coast/dunes/index.htmlSlide9
http://www.nps.gov/archive/grsa/resources/images/photos/dune_pattern03.jpg
Wind blows sand and makes ripples
Once sand begins to pile up,
ripples and dunes can form. Slide10
Ripples grow into dunes with increase of wind
and sand input
http://geology.wr.usgs.gov/parks/coast/dunes/index.htmlSlide11
The collapsing sand comes to rest when it reaches just the right steepness- 30 to 34 degrees, or angle of repose- to keep the dune stable.
http://geology.wr.usgs.gov/parks/coast/dunes/index.htmlSlide12
Sand blowing off a dune
http://www.uoregon.edu/~millerm/depenv.htmlSlide13
Animation
http://highered.mcgraw-hill.com/sites/0072402466/student_view0/chapter13/animations_and_movies.html#Slide14
Migration
sand inches up the windward side to the dune crest
then slips down the dune's
slip face
the dune to inches forward, migrating in the direction the wind blows
this leaves its mark on the internal structure of the dune.
http://geology.wr.usgs.gov/parks/coast/dunes/index.htmlSlide15
Cross-bedding preserved in sandstone
http://www.wwnorton.com/college/geo/egeo/flash/5_1.swf
http://geology.wr.usgs.gov/parks/coast/dunes/index.htmlSlide16
Navajo SandstoneSlide17
Cross bedding in the Navajo Sandstone
Arches National ParkSlide18
Star Dune Complex
The wind blows from different directions throughout the year.
http://www.nps.gov/archive/grsa/resources/images/photos/dunes_cristos03.jpgSlide19
Main Dune field at White Sands National Monument
http://www.nps.gov/archive/grsa/resources/images/photos/landscape_sw02jpg.jpgSlide20
http://www.nps.gov/archive/grsa/resources/photos_landscape.htmSlide21
http://www.nps.gov/archive/grsa/resources/photos_landscape.htmSlide22
http://www.nps.gov/archive/grsa/resources/photos_landscape.htmSlide23Slide24
Ventifacts
http://earthsci.org/education/teacher/basicgeol/windes/ventifact.gifSlide25
Features caused by wind
Ventifacts
rocks flattened and smoothed by wind abrasionSlide26Slide27
Features caused by wind
Desert pavement
Surface where wind has blown away the smaller sediment
Deflation
: removal of silt, sand, and clay by windSlide28
Desert Pavement
http://media-2.web.britannica.com/eb-media/28/10728-004-83F5D724.jpgSlide29
http://www.uwgb.edu/DutchS/geophoto/aeolian/DPAVMT1.jpgSlide30
http://www.goldengatephoto.com/jpeg/99-29-7.jpgSlide31
Evidence of wind
abrasion:
frosted grains
http
://en.wikipedia.org/wiki/File:WhiteSandsGypsum.jpgSlide32
Loess
Wind-blown silt deposits
Often forms thick layers as wind deposits small particles swept from glacial outwash plains
http://en.wikipedia.org/wiki/File:LoessVicksburg.jpgSlide33
“When the Yellow River runs clear”
Means the same as
“When Pigs fly”
http://upload.wikimedia.org/wikipedia/commons/e/ea/Hukou_Waterfall.jpgSlide34
http://en.wikipedia.org/wiki/File:Loess_landscape_china.jpgSlide35
The photograph below shows a sand dune that formed in a coastal area.
This sand dune was most likely formed by
(1) water flowing from the left
(2) water flowing from the right
(3) wind blowing from the left
(4) wind blowing from the rightSlide36Slide37
Draw the sand