"The existence of vast quantities of ""oil shale"" has been known in the area of what is now Colorado, Wyoming, and Utah as long as man has inhabited these areas. The local Indians discovered that certain types of rock would literally burn and make an adequate (albeit smoky) campfire. In 1918, the National Geographic(1) waxed eloquent over the potential of oil locked in the rocks that, by this time, had been identified by geologists as the ""Green River Formation."" Recent estimates by the U.S. Geological Survey indicate that the Green River Formation is the world's largest deposit of hydrocarbons, potentially exceeding the fields of the Middle East, the North Sea, and Alaska by several orders of magnitude. The Green River Formation, taken as an entity, is estimated to contain the equivalent of 1.8 trillion barrels of oil, in shale that contains 15 or more gallons of oil to the ton. If only the higher quality components of the formation are considered, approximately 600 billion barrels of shale oil have been identified, using over 25 gallons of oil per ton of shale as a criterion for establishing high-grade occurrences. Oil shale occurs in many parts of the United States as shown in Figure 1-1. The estimated equivalent barrels of oil in place for the major shale formations are also shown in Figure I-I. The richer shales are located in the Green River Formation; details of this formation are shown in Figure I-2."