What Are Tar Sands? | Union of Concerned Scientists
· Tar sands are an increasingly common—but expensive and dirty—source of oil. Tar sands (also known as oil sands) are a mixture of mostly sand, clay, water, and a thick, molasseslike substance called bitumen. Bitumen is made of hydrocarbons—the same molecules in liquid oil—and is used to produce gasoline and other petroleum products.