Every day now either on TV broadcasts, in print media or on the Internet some mention is made about our reliance on fossil fuels for our energy needs. What are they? How were they made? How did they get where they are today? They are, of course, crude oil, coal and natural gas.

The skyrocketing price of gasoline is getting most of the media’s attention, but the prices of coal and natural gas have also been rising at a rapid clip. Speculation by investors in stock futures markets around the world undoubtedly has contributed somewhat to these price increases but economic pressure from increased demand without increased supply is causing most of it. Gasoline, diesel fuel, heating oil, paint solvents, roofing materials, soaps, toiletries, plastics and a myriad of other products start out as crude oil pumped from underground reservoirs and delivered to refineries where it is processed into a variety of products that are further processed into all of the ones above. How did the oil get into the reservoirs?

Coal, crude oil, and natural gas (methane) were all formed millions of years ago in tropical regions. Until 200 million years ago, most plants and animals lived and died in these regions. Coal deposits around the Earth today were produced by tropical plants that lived around 300 million years ago. Many giant ferns and large club mosses grew in swamps where they eventually died and replaced by new ones. As they died they fell in the swampy water. This process continued until eventually there was a thick layer of decomposing plants. In time, sediments and dirt covered these layers. Millions of years later, heat and pressure from the overlying layers converted the decomposed plants to coal.

Coal is mostly carbon but contains some residual nitrogen that the plants once used as a nutrient and some sulfur from minerals that were dissolved in the swampy water. Whenever coal is burned the carbon is converted to carbon dioxide and carbon monoxide, both of which contribute to global warming, and the nitrogen and sulfur are converted to their oxides which react with water in the air to form nitric and sulfuric acids. The acids then fall to Earth as acid rain, doing damage to plants and acidifying lakes, rivers, and streams where they damage marine life.

Even though coal deposits are the result of decaying tropical plants, they are found in many places that are not now tropical. They have even been found in Antarctica, which indicates Antarctica must have been located near the equator at one time in Earth’s history. Fossilized logs of tropical trees have been found embedded in coal deposits located thousands of miles from today’s tropical regions.

Oil and natural gas (methane) deposits were also formed millions of years ago in tropical regions. The fact that oil and natural gas deposits are now found in Alaska and Russia is further evidence that the continents all were at one time located around the equator. Vast quantities of marine plant materials and zooplankton, that was composed of phospholipids, died in shallow seas and sank into the mud under anaerobic (without oxygen) conditions that prevented biodegradation. Bacteria converted the lipids (oil,fats,waxes) into a waxy substance called kerogen. As this layer was buried deeper, pressure raised the temperature, which broke up the kerogen into straight-chained hydrocarbons that make up crude oil. Once the oil formed it either became trapped in an oil reservoir or escaped upward into soil that biodegraded it. Any oil buried deeper would have a greater pressure and temperature and would be broken down further into natural gas.

Read Settled Science to learn more how other powerful geothermal and geophysical forces have shaped the world in which we live.

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