BRUNEAU SAND DUNES
In the Eagle Cove Depression
of southern Idaho's Snake River Plain is 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%) & Fe-Mg minerals (~12%). The sediment is 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. So, they post-date the draining of ancient Lake Bonneville (the
Pleistocene precursor to Great Salt Lake in northern Utah). The larger
sand dunes here are partly stabilized by vegetation along the bases. The
tallest sand dunes stand over 400' above the level of a nearby lake. Two
dunes alone here cover ~600 acres worth of land.
Bruneau Sand Dunes, Eagle Cove Depression,
southern Idaho, USA.
Bruneau Sand Dunes, Eagle Cove Depression,
southern Idaho, USA.
Bruneau Sand Dunes - lateral view of one of
the dunes. Wind generally blows from left to right. The left slope
(windward face) has obvious ripple crests. The right slope (slipface) has
small-scale avalanche chutes (darker gray areas).
Bruneau Sand Dunes - ripple crests on sand
flats.
Bruneau Sand Dunes - vertebrate tracks (birds
& mammals) on sand flats.
Synthesized from info. in
Murphy (1973) & info. provided by Bruneau Dunes State Park.