In the United States, coal is mined in 25 states and three major regions. The largest coal reserves are in the United States, Russia, China, Australia, and India. About 3 meters (10 feet) of layered vegetation eventually compresses into a third of a meter (1 foot) of coal!Ĭoal exists in underground formations called “ coal seams” or “coal beds.” A coal seam can be as thick as 30 meters (90 feet) and stretch 1,500 kilometers (920 miles).Ĭoal seams exist on every continent.

Carbonization takes place under incredible heat and pressure. Under the right conditions, peat transforms into coal through a process called carbonization. Peat itself can be burned for fuel, and is a major source of heat energy in countries such as Scotland, Ireland, and Russia. Peat bogs store massive amounts of carbon many meters underground. These areas of buried plant matter are called peat bogs. Due to this, the plant matter decomposed at a very slow rate and retained most of its carbon (source of energy). Mud and acidic water prevented the plant matter from coming into contact with oxygen. Over time, the plants (mostly mosses) and algae were buried and compressed under the weight of overlying mud and vegetation.Īs the plant debris sifted deeper under Earth’s surface, it encountered increased temperatures and higher pressure. The seas occasionally flooded the forested areas, trapping plants and algae at the bottom of a swampy wetland. During this time, the Earth was covered in wide, shallow seas and dense forests. The conditions that would eventually create coal began to develop about 300 million years ago, during the Carboniferous period.

Because coal takes millions of years to develop and there is a limited amount of it, it is a nonrenewable resource. It is composed mostly of carbon and hydrocarbons, which contain energy that can be released through combustion (burning).Ĭoal is the largest source of energy for generating electricity in the world, and the most abundant fossil fuel in the United States.įossil fuels are formed from the remains of ancient organisms. Coal is a black or brownish-black sedimentary rock that can be burned for fuel and used to generate electricity.

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