9781422285596

10 Natural Gas

Phytoplankton viewed through a microscope. These are called diatoms; they are the most common type of phytoplankton.

Usually, when living things die, they are scavenged and rot away, and the minerals and other substances from their bodies are recycled naturally into new life. At certain times in the distant past, however, in warm shallow waters with plenty of nutrients and minerals, decay and recycling did not happen fast enough. As a result, dead remains began to accumulate on the bottoms of seas and lakes. As they piled up, low-oxygen conditions meant that certain kinds of microbes, called methanogenic bacteria, could thrive. They managed to rot and break down some of the remains of living things, producing methane gas in the process. The lower layers of rotting remains were gradually squeezed harder and harder by the weight of more layers above; this pressure raised their temperature, too. As the layers gradually turned into rock, what was left of the plankton broke down even further, being essentially “slow cooked” by a process called catagenesis. They formed substances called kerogens , which have a slimy or waxy nature. Kerogens are made of the two chemical substances (elements) hydrogen (H) and carbon (C). So they are known as hydrocarbons .