wind erosion & deposition

WED V15

WIND EROSION & 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 Earth’s surface

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1903/es1903page01.cfm?chapter_no=visualization

FEATURES CAUSED BY WIND

Ripples and dunes

Windward side is gentle

Leeward side is steep

http://geology.wr.usgs.gov/parks/coast/dunes/index.html

FOR DUNES & RIPPLES TO FORM YOU NEED…

Wind Dry sand Wind break (drift wood, dead

bird, plant, etc.)

DUNES

http://geology.wr.usgs.gov/parks/coast/dunes/index.html

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, CAhttp://www.uoregon.edu/~millerm/sanddunes.html

GRASSES ON THE DUNES HELP STABILIZE THE BEACH

http://geology.wr.usgs.gov/parks/coast/dunes/index.html

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.

RIPPLES GROW INTO DUNES WITH INCREASE OF WIND

AND SAND INPUT

http://geology.wr.usgs.gov/parks/coast/dunes/index.html

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.html

SAND BLOWING OFF A DUNE

http://www.uoregon.edu/~millerm/depenv.html

ANIMATION

http://highered.mcgraw-hill.com/sites/0072402466/student_view0/chapter13/animations_and_movies.html#

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.html

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.html

NAVAJO SANDSTONE

CROSS BEDDING IN THE NAVAJO SANDSTONE

ARCHES NATIONAL PARK

STAR DUNE COMPLEX

The wind blows from different directions throughout the year.

http://www.nps.gov/archive/grsa/resources/images/photos/dunes_cristos03.jpg

MAIN DUNE FIELD AT WHITE SANDS NATIONAL MONUMENT

http://www.nps.gov/archive/grsa/resources/images/photos/landscape_sw02jpg.jpg

http://www.nps.gov/archive/grsa/resources/photos_landscape.htm

http://www.nps.gov/archive/grsa/resources/photos_landscape.htm

http://www.nps.gov/archive/grsa/resources/photos_landscape.htm

VENTIFACTS

http://earthsci.org/education/teacher/basicgeol/windes/ventifact.gif

FEATURES CAUSED BY WIND

Ventifacts rocks flattened and smoothed

by wind abrasion

FEATURES CAUSED BY WIND

Desert pavement

Surface where wind has blown away the smaller sediment

Deflation: removal of silt, sand, and clay by wind

DESERT PAVEMENT

http://media-2.web.britannica.com/eb-media/28/10728-004-83F5D724.jpg

http://www.uwgb.edu/DutchS/geophoto/aeolian/DPAVMT1.jpg

http://www.goldengatephoto.com/jpeg/99-29-7.jpg

EVIDENCE OF WIND ABRASION: FROSTED GRAINS

http://en.wikipedia.org/wiki/File:WhiteSandsGypsum.jpg

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.jpg

“When the Yellow River runs clear”

Means the same as

“When Pigs fly”

http://upload.wikimedia.org/wikipedia/commons/e/ea/Hukou_Waterfall.jpg

http://en.wikipedia.org/wiki/File:Loess_landscape_china.jpg

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 right

DRAW THE SAND