geography final project
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![Page 1: Geography Final Project](https://reader033.vdocuments.site/reader033/viewer/2022052823/55571629d8b42a067f8b461e/html5/thumbnails/1.jpg)
Great Sand Dunes National Monument
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Background• Located between the San Juan and Sangre de Cristo
Mountains in Southwestern Colorado’s San Luis Valley
• Over 12,000 to 130,000 years old (exact time they formed is unknown)
• Approximately 42,000 acres
• Composed of black magnetite, pink feldspar, red and tan sandstone, green epidote, white quartz, and many other minerals.
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Medano CreekFluvial Process
• Seasonal stream that runs through the national monument
• Created from mountain run off and seasonal rain, this determines the volume of flow.
• Moisture from the creek keeps dunes stabilized so they don’t move
• “Conveyor belt for sand”- flow carries sand downstream and when the creek dries up the wind blows the sand back to the dunes
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Drying up Light Flow
Heavy Flow
Different flows of Medano Creek
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Wind (aeolian) TransportationArid Land
• Dunes are created by a combination of wind patterns. Northeast wind blows strongly across the valley, weaker winds blow southwest through a gap in the mountains
• Particles are moved by saltation and traction or in other words bounced and rolled
• The surface layer moves slowly downward as a result of saltation, this is called creep
• When the sand is deposited (known as aeolian deposition) it creates a sand dune
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Aeolian Transportation Diagram
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Different Types of DunesStar Dune
Seifs
Barchan
Transverse Dunes
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Where all the Sand Came FromGlacial Modification of Terrain
• During the Pleistocene Epoch the San Luis Mountains were covered in glaciers
• Relatively warm summers during this time and the melting glacier seasonally flooded the valley
• Glacial plucking occurred as the glaciers moved down the mountain which is when the glacier picks up rocks and sand
• Meltwater carried tons of sand that the glaciers had scoured from the mountains and deposited it in an alluvial fan
• Winter winds carried the sand across the valley
• The Sangre de Cristo Mountains blocked the wind and the sand piled up forming the dunes.
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Glacier of a Mountain Alluvial FanCaused from Meltwater
Glacial Plucking
Wind Blowing and Moving Sand
Sand Dunes are Formed