The great sand dunes
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Transcript of The great sand dunes
THE GREAT SAND DUNES
By Amalia McCoyGEO 111
Spring 2012
The Great Sand dunes of Colorado are the tallest in North America.
Rising about 750 feet Covering roughly 30 square miles
EARTH’S NATURAL PROCESS
Formed by sand and soil deposits of the Rio Grande and other streams and smaller rivers which flow into the Rio Grande
Western winds picked up the sand and soil deposits from the River’s flood plain
The wind loses power right before crossing the Sangre de Cristo Range
The sand was deposited on the eastern edge of the valley
The wind changes the formation and shapes of the dunes daily
AEOLIAN DEPOSITION
Definition: Sand and dust moved by the wind are eventually deposited when the wind dies down.
Image taken from: http://web.ncf.ca/jim/sand/overview/grainflowAnimation.gif
SLIP FACE The steeper leeward face of a sand dune
Image taken from: http://www.geocaching.com/seek/cache_details.aspx?guid=c93e835c-617b-4c33-bc61-1e2b484e267a
•Wind erodes the windward side of the dune which force the grains of sand up and over the crest to be deposited on the other side
•Maintains an angle of 32 degrees- 34 degrees.
STAR DUNES
• Formed by multidirectional winds
•Have 3 or 4 arms
•Large pyramid shape dunes
BARCHAN DUNES
• form in places where there is limited sand and a constant wind direction
•crescent-shaped dunes that concave downwind
•Face the prevailing wind
Image taken from: http://www.nps.gov/grsa/naturescience/images/star_dune_formation.jpg
Image taken from: http://www.indiana.edu/~geol116/Week11/dunes2.jpg
•become aligned together along a plane perpendicular to the wind
•Occur where the supply of sand is greater than that of where barchans are formed
•Face the prevailing wind
Image taken from: http://web.arc.losrios.edu/~borougt/DesertDiagrams.htm
SEIF DUNES
Image taken from: http://icons-ak.wunderground.com/data/wximagenew/e/Eaglz/196.jpg
Image taken from: http://giltphoto.com/images/Colorado/Great%20Sand%20Dunes%20National%20Park/GreatSandDunes35w.jpg
Image taken from: http://digital-desert.com/natural-formations/SDGfig4.gif
•Linear or longitudinal dune
•Represents an intermediate direction between 2 dominate wind directions, blowing from one direction part of the year and another direction the rest of the year
•Usually parallel
TRANSVERSE DUNES
FLUVIAL PROCESS •The Medano Creek that flows next to the Sand dunes, is an Intermittent Stream
•Intermittent stream- is known as a seasonal stream where water flows for ONLY part of the year.
•When the water level is low the stream has braided channels
•Braided channels- consisting of multiple interwoven and interconnected channels that are separated by low bars or islands of sand, gravel and other lose debris.
•During the winter and wet seasons the stream fills up
•The stream carries and deposits sand
•Deposition- whatever is picked up must be set down
DEFLATION AND ABRASION
Deflation- the overall shifting of lose debris either through air or along the ground
Abrasion- wind forces the particles of sand against the mountains with such force that a sand blasting effect takes place and erodes the surface of other rocks and the Sangre de Cristo Mountains.
The landscape is constantly changing
BIBLIOGRAPHY
http://en.wikipedia.org/wiki/Great_Sand_Dunes_National_Park_and_Preserve http://www.indiana.edu/~geol116/Week11/wk11.htm http://mycolorado.org/sand_dunes.html http://www.americansouthwest.net/colorado/great_sand_dunes/national_monu
ment.html http://web.ncf.ca/jim/sand/overview/grainflowAnimation.gif http://www.geocaching.com/seek/cache_details.aspx?guid=c93e835c-617b-4c3
3-bc61-1e2b484e267a http://www.nps.gov/grsa/naturescience/images/star_dune_formation.jpg http://www.indiana.edu/~geol116/Week11/dunes2.jpg http://giltphoto.com/images/Colorado/Great%20Sand%20Dunes%20National%2
0Park/GreatSandDunes35w.jpg http://web.arc.losrios.edu/~borougt/DesertDiagrams.htm http://icons-ak.wunderground.com/data/wximagenew/e/Eaglz/196.jpg http://digital-desert.com/natural-formations/SDGfig4.gif