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In Cooperation With
Welcomes You To The El Mirage Dry Lake Bed
An alluvial fan is a triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt. This sediment is called alluvium. Alluvial fans are usually created as flowing water interacts with mountains, hills, or the steep walls of canyons. Streams carrying alluvium can be trickles of rainwater, a fast-moving creek, a powerful river, or even runoff from agriculture or industry. As a stream flows down a hill, it picks up sand and other particles—alluvium.
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The rushing water carries alluvium to a flat plain, where the stream leaves its channel to spread out. Alluvium is deposited as the stream fans out, creating the familiar triangle-shaped feature. The narrow point of the alluvial fan is called its apex, while the wide triangle is the fan's apron. Alluvial fans can be tiny, with an apron of just a few centimeters spreading out from the trickle of a drainpipe. They can also be enormous.
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Alluvial fans can be very diverse habitats. Shrubs such as rabbitbrush and greasewood, or even trees such as ash or willow, are common in the area of alluvial fans. These plants have very deep roots, which can access the water that helped create the alluvial fan, but has now sunken far below it.
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To log a find on this cache, you must E-MAIL me the correct answers. If any of your answers are wrong, I will email you and let you know.
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1. Put "El Mirage Dry Lake Bed - Alluvial Fan" in the subject line of your email.
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2. What type of alluvium do you see in the area?
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3. At the above coordinates, what type of shrubs/plants/trees are most common?.
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4. Where do you think this alluvial fan starts and why there?
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5. Optional: Post a picture of you at El Mirage.
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Works Cited
http://www.blm.gov/ca/st/en/fo/barstow/mirage.html
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https://en.wikipedia.org/wiki/Alluvial_fan
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http://www.fema.gov/media-library-data/20130726-1504-20490-3060/fema165.pdf
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http://education.nationalgeographic.org/encyclopedia/alluvial-fan/
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http://pubs.usgs.gov/of/2004/1007/fans.html
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