English: The Eagle Cove Depression of southern Idaho's Snake River Plain has a concentration of fairly large sand dunes, including the largest single-structured dune in all of North America. The sand is dominantly quartzose (~62%) with minor feldspar (~26%) & ferromagnesian minerals (~12%). The sediments are derived from erosion of Bruneau Formation & Glenns Ferry Formation rocks (Idaho Group, Plio-Pleistocene).

The sand dunes at Eagle Cove are fairly young - they were deposited by winds during the last 11,000 years. As such, they post-date the draining of ancient Lake Bonneville, which is the Pleistocene precursor to Utah's Great Salt Lake. The larger sand dunes here are partly stabilized by vegetation along the bases. The tallest sand dunes reach >400 feet above the level of a nearby lake. Two dunes alone here cover ~600 acres worth of land.

At left in the photo is the windward face of the sand dune. Sand is blown upward along the windward face, which is the shallow-sloped side of a sand dune. Sand accumulates at the summit until oversteepening causes small sand avalanches that generally form relatively narrow chutes and lobes. The steeper side of a sand dune is the leeward face, or slip face. Cross-beds form by sand deposition along dune slip faces.

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Site-specific info. synthesized from: Murphy (1973) - The Geology of Eagle Cove at Bruneau, Idaho. M.S. thesis. State University of New York at Buffalo. 77 pp. &

from info. provided by Bruneau Dunes State Park.