On the Western Slope of Colorado's Rocky Mountains, local lore tells of an early settler named Mike Callahan who built his home in the shadow of the Book Cliffs along Parachute Creek in 1882. He cut and assembled sturdy local pines into a log cabin. To heat his new home, he built a fireplace and chimney out of the abundant and easily-quarried rocks he found on nearby hills. When his work was complete, he threw a housewarming party that turned into a tragically bad pun (some might say metaphor) when the fire he lit in the hearth quickly spread up through the mahogany-colored chimney rocks and set the entire house ablaze.1
Although nobody told Mr. Callahan until it was too late, the dark-hued shale rocks found in pockets along the Western Slope boast a high concentration of petroleum-like kerogens that will ignite when exposed to enough heat. While oil shale, a convenient umbrella term for a variety of fine-grained and organic-laden sedimentary rocks, formed in prehistoric lakebeds in a process similar to oil, it has not (yet) been subject to enough heat and pressure to be transformed into a liquid state.
Given a few million more years, the kerogens trapped in the Western Slope shale may become liquid oil. But an influential combination of energy companies and politicians - all responding to the energy demands of American citizens, we should remember - would prefer not to wait for nature to take its course. They are inclined to speed up the process with the application of human ingenuity.