But fossil fuels exist in finite supply. Eventually they will run out. Coal and oil formation are continuing in the Earth even now, but it is a very slow process, taking millions of years, not at all comparable with the speed at which we are burning the existing supplies. The fossil fuel that will probably last the longest is coal. However, coal burning produces a great deal of pollution, even more than burning oil does, so it is not an ideal solution to our energy supply problem.
All fossil fuels produce air pollution to some extent, even natural gas, which is the cleanest.
California Historical Energy Statistics gives a great deal of statistical information on petroleum, natural gas, and electricity in the state. Interesting Facts about Oil and Gas from the Department of Conservation. 1997 Oil and Gas Statistics for California. How Fossil Fuels Formed covers coal, oil, and natural gas. From the US Department of Energy.