The Athabasca Oil Sans are a large deposit of oil-rich bitumen, or extremely heavy crude oil, located in northern Alberta, Canada. These oil sands consist of a mixture of crude bitumen (a semi-solid form of crude oil), silica sand, clay minerals, and water. The Athabasca deposit is the largest of three major oil sands deposits in Alberta, along with the nearby Peace River and Cold Lake deposits. Together, these oil sand deposits cover about 141,000 square kilometres (54,000 sq mi) of sparsely populated boreal forest and muskeg (peat bogs) and contain about 1.7 trillion barrels (270×109 m3) of bitumen in-place, comparable in magnitude to the world's proven reserves of conventional petroleum.