A hypnotic maze of subdivisions stretches along Anderson Mill Road as you drive north out of Austin. Then, just before you reach downtown Cedar Park, towering mounds of loose rock rise like ashes from a giant cigarette. Throughout the Texas Hill Country, this sort of pitted, alien topography is increasingly common. The massive craters result from the mining of what’s known as aggregate—sand, gravel, crushed stone, and many other particulates that are used to make building materials such as glass, asphalt, and concrete.

Read more from Mac Carey with Texas Monthly here.