In western Mongolia, braided streams of sand dunes stretch east-west
across the arid landscape. One ribbon of sand, spanning roughly 200
kilometers, extends from an area south of Khyargas
Lake in the west to a smaller lake, Telmen Nuur, in the east. In
between, sand dunes march past Har Nuur, or “Black Lake.”
The Advanced Land Imager (ALI) on
NASA’s Earth Observing-1 (EO-1) satellite captured this
natural-color image of Har Nuur on June 12, 2010. Camel-colored sand
dunes ripple along the lake’s northern shore. Along the southern
shore, sand dunes approach the lake in just two locations. A
triangle-shaped expanse of sand borders Har Nuur in the east, and a
tongue of sand intrudes into the lake in the west, pushing through a gap
in the nearby mountains. All of the sand dunes, however, form part of a
larger dune field nearly encircling the lake.
Har Nuur sits in the Valley
of Lakes of western Mongolia. Bordered by multiple
mountain ranges, the Valley of Lakes hosts remnant basins of larger
ancient lakes, dune fields, and salt marshes. Har Nuur, like other lakes
in the region, is a closed-basin lake fed by precipitation.
Hot, dry summers prevail in this part of the word, with frequent, hot
winds blowing from the northwest. Winds push the sand dunes eastward
past Har Nuur and the nearby mountains. The long, skinny dune field
pushing into the lake is a persistent feature. It was equally obvious
when astronauts on the International Space Station photographed Har Nuur in 2006.