What are tar sands? | American Geosciences Institute
2021-8-15 · Tar sands (also called oil sands) are a mixture of sand, clay, water, and bitumen. Bitumen is a thick, sticky, black oil that can form naturally in a variety of ways, usually when lighter oil is degraded by bacteria. Bitumen has long been used in waterproofing materials for buildings, and is most familiar today as the binding agent in road asphalt.