A pair of empty docks sit atop dried muck at an abandoned marina, glaring reminders that the largest saltwater lake in the Western Hemisphere is disappearing. Three main tributaries empty into Utah’s Great Salt Lake, but decades of their flows being diverted for agriculture, cities, and industry—along with prolonged drought—have starved the 1,700-square-mile body of its lifeblood. Last summer the inland sea made national headlines when it dropped to the lowest point ever recorded, exposing roughly 750 square miles of sediment to the same winds that carve hoodoos and sculpt arches to the south and east.
Despite much-needed rain on this early-October afternoon, only the slimmest sheen of water glistens where the lake should be—and it will disappear within days. The patches of bare earth it will leave behind can easily turn into dust that blows straight into Utah’s largest urban area, Salt Lake City, about 30 miles to the east. Making matters worse, that sediment is full of arsenic.
Kevin Perry, an atmospheric scientist at the University of Utah in Salt Lake City, has covered nearly every inch of this sandy terrain riding (sometimes pushing) a fat-tired bicycle to sample and identify the most erodible patches. Between 2016 and 2018, he pedaled 2,300 miles—dodging lightning, bullets from trigger-happy target shooters, and roaming bison on Antelope Island, a state park that juts into the southeastern corner of the lake. And he got caught in 15 or so of the increasingly frequent dust storms on the dried lake bed, or playa. “My legs were sandblasted,” he says. “Visibility reduced to feet in minutes. Sand was in my eyes.”
By documenting the amount of vegetative cover, the presence and thickness of any biological crust produced by bacteria, algae, or mosses, and the percentage of tiny dust-prone silt and clay particles, Perry determined that 9 percent of Great Salt Lake sediments readily blow away. But as much as 22 percent could—especially if human activities, such as the use of roving all-terrain vehicles or motorcycles, destroy the crust. Perry, a meteorologist by training, estimates Salt Lake City annually gets 10 to 15 notable dust events that reduce visibility to less than a mile, up from none only 15 years ago. He has to approximate because the sensors required to monitor air quality are few in number, not well placed for his purposes, and set to measure only one 24-hour period every three days, to keep costs low. Even if dust storms are happening all the time, you have only a 1-in-3 chance of being able to measure one, he says.
Perry is part of a team of six scientists aiming to track dust, both the extent to which it moves in acute storms and the incognito chronic creep of microscopic granules called particulates…