Where resources are found

Coal was formed by the decomposition of large land plants and trees buried under the earth about 300 million years ago. At that time, the earth had dense forests in low lying wet land areas. Due to natural processes like earthquakes, volcanoes, and floods, these forests were buried under the surface of earth and got compressed due to the deposition of soil over it. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted into coal. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation. Since it was formed from the remains of vegetation, coal is also called a fossil fuel.Petroleum was formed by the decomposition of the remains of the tiny plants and animals buried under the sea millions of years ago. When the tiny plants and animals died, their bodies sank to the bottom of the sea and were soon covered with mud and sand. Due to high pressure, heat and action of bacteria, in the absence of air, the dead remains of tiny plants and animals were slowly converted into petroleum. The petroleum thus formed got trapped between two layers of impervious rocks, forming an oil deposit.