Sand Dunes of Tatooine EarthCache
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"That malfunctioning little twerp. This is all his fault. He tricked me into going this way but he'll do no better."
To log this Earthcache, walk out to a sand dune greater than head high. Bonus points for venturing to the highest dune. The new parking area is ~2 miles east of Stove Pipe Wells. Dunes are found from 0.2 to 1 mile from the paved highway.
Complete the following tasks:
1. Post the coordinates and elevation of the selected dune crest.
2. Determine the slip face of the dune, and report the opposite, prevailing wind compass direction.
3. If the selected dune is a multiple ridge “star” dune, report that.
A caution: C-3PO forgot to bring a quart of water and sun protection (brimmed hat, sunglasses, sunscreen, lipbalm).
Sand dunes accumulate in surprisingly only a few places in Death Valley National Park. Sand dunes occur at Mesquite Flat, Eureka Valley, Panamint Valley, and the Ibex dunes near Saratoga Springs. The most accessible dunes to paved road are at Mesquite Flat very near the Stove Pipe Wells Ranger Station.
The primary source of sand for the dune sands is the Cottonwood Mountains to the northwest (1). Tiny grains of quartz and feldspar are formed as flash floods rake the mountain slopes and gullies, and grind the rock to smaller pieces as they move toward the valley floor. At the valley floor, the heaviest rocks are deposited at the top of alluvial fans, and smaller and lighter materials are spread across the bottom of the fans.
Prevailing winds from the northwest lift the grains of sand, tossing them along close to the ground, not unlike leafs blown by a leafblower. Most blowing sand remains within a meter of the surface as it migrates. Dunes accumulate where the wind speed drops due to large topographical features or even small local features such as vegetation. As with wind over the surface of ocean, the longer the fetch length and the faster the wind speed, the larger and stronger the wave of sand will be. Wind pushes sand up to the top of the pile until the pile is so steep that it collapses under its own weight. The collapsing sand comes to rest when it reaches just the right steepness to keep the dune stable. This angle, usually about 30-34°, is called the angle of repose. Every pile of loose particles has a unique angle of repose, depending upon the properties of the material. Sand dunes move downwind, as grains inch up the windward side to the dune crest, then slip down the dune’s slip face.
Additional dune info: At several dozen locations around the world, sand dunes are said to sing, producing baffling booming or humming sounds. Throughout recorded time, travelers report the phenomenon in the Gobi Desert, the Sahara, the Chilean desert, and even Death Valley. It is believed that uniformly sized, very round grains of sand rub against one another to produce a frequency of sound (2). The sound is amplified in the largest dunes. Purported singing dunes in and near Death Valley include Eureka, Dumont, and Kelso… but not Mesquite Flat.
(1.) nature.nps.gov/geology/usgsnps/deva/ftdune1.html (visit link)
(2.) pbs.org/wgbh/nova/earth/booming-sands.html (visit link)
Robert P. Sharp, Geology Underfoot in Death Valley, 1997.
Robert Decker, Road Guide to Death Valley National Park.
Marli Miller and Lauren Wright, Geology of Death Valley: Landforms, Crustal Extension, Geologic History, Road Guides 2006.
Michael Collier. Introduction to Geology of Death Valley, (visit link)
Thank you, Ranger Stephanie Kyriazis, geologist and NPS Education Specialist.
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