Sand is the very image of abundance, our standard rule-of-thumb metric for imagining the number of stars in the universe or molecules in a drop of water.
Half a billion years later, the climate had cooled, the seas had receded; a vast ice sheet crept down the continent from the Canadian shield, depositing a layer of “drift”—glacial tillage, consisting of material plowed up, transported, and deposited by advancing and retreating ice.
Throughout much of the northern Midwest, the sand now lies buried beneath the glacial drift. But the area of the Sand Counties—in a region stretching from central Wisconsin into Iowa and Illinois today—was never touched by the glaciers.  Today a soft corduroy of low hills and ancient seabed blankets the region, which is also called “the Driftless Area,” as it lacks the deep, level bed of drift—now a rich soil – which makes the rest of the Midwest a flatland fit for corn and beans.
In the fullness of deep time, living matter from such ancient ecosystems coalesced over aeons into shale beds harboring oil and natural gas. In recent years, the controversial process of hydraulic fracturing or “fracking” has opened up these deep shales to human exploitation—and the lands above, and the people who live there, to a panoply of hazards, from earthquakes to hazardous waste.
There are no oil shales in Wisconsin. But the ancient sands of the Driftless Area have a role in fracking: with their small, round grains, they make an ideal “proppant” medium which, poured into wellheads, holds open fissures in the rock for gas and oil extraction.
So called “frac sand” mines are a fixture in south-central Wisconsin today. And they, too, have their environmental consequences: the mines scar the fields and farmlands; the silky, round-grained sand is so fine that it can billow into the air.
Matthew Battles is associate director of metaLAB, a creative research agency based at Harvard's Berkman Center for Internet and Society. He is the author of several books, the most recent of which is Palimpsest: A History of the Written Word (Norton 2015).