BLACK ROCK DESERT, an arid region in Humboldt and Pershing counties, Nevada, U.S.A., about Tom. long and in some places 2om. wide, embracing an area of about i,000 sq. miles. The belt of greatest aridity (less than 4in. of rainfall annually) extends from the north-east to the south-west just east of the Pine Forest and Black Rock mountain ranges. The desert serves as the "sink" of the Quinn river, and, at times, is largely covered with water only a few inches deep. When the water evaporates in the summer it leaves a clay-bed of remarkable hardness, which is frequently encrusted with saline matter of a snowy whiteness. This barren plain is practically devoid of vegetation, and from its surface alkaline dust is blown into vast clouds by the summer winds.