In Close Range: Wyoming Stories, Annie Proulx writes: “It was impossible to run cows in such tough country where they fell off cliffs, disappeared into sinkholes.” A sink, or sinkhole, is a closed depression that is dry or through which water seeps or flows, resembling in shape a basin, funnel, or cylinder. Sinkholes develop by solutional processes or from collapse into subsurface voids. On the Mitchell Plain in southern Indiana, most trees that remain in the fields are in sinkholes whose slopes are too steep for clearing and plowing. The Big Lost River of Idaho comes out of the mountains and sinks into the porous basalt flows of the Snake River Plain. The December Giant Sinkhole, 400 feet wide and 150 feet deep, formed in 1972 near Montebello, Alabama, was most likely a collapse of surface material into an underlying limestone cavern. At least fifty synonyms have been recorded, including doline, shakehole, swallet, swallow pit, leach hole, interior basin, and sotch. A desert sink, such as the Carson Sink in Nevada, is a depression where a desert stream ends or disappears by evaporation. Glacial sink is an obsolete term for a depression in a terminal moraine. A volcanic sink, or pit crater, is a circular depression on the flank of a volcano, formed by collapse. Not all sinks are naturally occurring, however. In Pittsburgh in the 1960s, underground mines caused surface land to sink, destroying neighborhoods. Less spectacular but more widespread is the surface shrinkage in the arid West caused by excessive pumping of underground water for overland irrigation, as has happened in Antelope Valley, California.

Kim Barnes