Large hunks of gypsum swept between two volcanoes
K. Benison/Geology 2017
\GRAV-uhl DEV-uhl \ n.
A whirlwind containing gravel-sized debris
Towering, crystal-filled twisters periodically swirl in a valley nestled between two volcanoes in the Andes Mountains, newly reported observations show. The odd weather events are the first record of large pieces of gravel efficiently moving across a landscape by suspension in air.
Geologist Kathleen Benison of West Virginia University in Morgantown spotted the whirlwinds during an expedition in 2007 to an otherworldly region of northern Chile. There, gypsum crystals form from evaporating volcanic pools of salty, acidic water. When the pools dry, exposing the crystals within, whirlwinds as big as half a kilometer across can sweep the crystals aloft, Benison reports online March 15 in Geology. She saw storms of crystals travel as far as five kilometers before dropping their payloads into large, dunelike piles.
Over time the far-flung crystals, some as long as 27 centimeters (which geologists still classify as gravel), meld together into a massive hunk. If found in the rock record, such crystal conglomerations could help geologists identify where strong whirlwinds howled long ago, Benison proposes.
K.C. Benison. Gypsum gravel devils in Chile: Movement of largest natural grains by wind? Geology. Published online March 15, 2017. doi: 10.1130/G38901.1.
T. Sumner. Virtual twister reveals possible source of tornado longevity. Science News. Vol. 188, September 19, 2015, p. 32.
T. Sumner. The greatest natural disaster that almost was. Science News Online, April 17, 2015.
T. Sumner. Central American fires may intensify U.S. tornadoes. Science News Online, January 28, 2015.