The story of coal begins a very long time ago with plants. Forests of pine and fir trees and beautiful lacy ferns and moss grew thickly over parts of our world soaking up the sunshine. Some would die and others would grow in their place, and the cycle would repeat, building up layers of dead plants. At some point they were covered by water and sand and dirt were laid down on top of them by the water. Water is heavy and it pressed everything down. The water also kept air from getting to the plants so they didn’t turn back into soil the way plants usually do when they die. Instead the dirt above and the soil beneath were squeezed down until they turned into rock leaving pictures of fern leaves, and tree trunks in the rock above, and fossil roots in the soil below. This is why coal is called a fossil fuel. We all know that rocks don’t burn. Sometimes we put them around a fire outside for that very reason. But you know that plants like trees do burn. And all those plants pressed down by the weight of rock above, and baked by the heat that comes from the centre of the earth, during many, many years turned into something that looks like black hard rock, yet it burns very well and gives off all the heat those plants stored up as sunshine all those many years ago.
There are four stages of coal and they are different depending on the amount of time, pressure and heat they have been subjected to. Peat is the first stage of coal. It only takes a few hundred years to form. It is layers of dead moss and bog plants, and contains a lot of moisture. It must be dried out before it will burn and then it gives off a lot of smoke and leaves a lot of ash. Lignite has a brown, woody texture. It is crumbly and very soft. It gives off little smoke, and is good for making briquettes. Bitumous is the kind of coal that is most often found in Nova Scotia. It is black, streaky and breaks easily. It still contains some of the plant oils and therefore gives off smoke when it is burned. It is the most commonly used coal as it burns well and produces a lot of heat. Anthracite is the most valuable form of coal. It is very hard and black and is an excellent fuel which is smokeless and leaves very little residue. However, it is found deep under the ground and is expensive to mine. Coke is made by taking bitumous coal and baking it until all the oil is removed leaving pure carbon which burns well.
There is coal in other places in Canada: the western plains and the foothills of the Rocky mountains. The coal in Nova Scotia is mostly under the ocean and is reached by underground tunnels. However, most of the coal mines in Canada are surface mines. Surface mines reach the coal by stripping off the top layers of soil and rock until they reach the coal underneath. In Canada, when the coal has been removed, the mining companies are required to make the land look the same as it did before it was mined.
PROJECT: Remembering that coal comes from dead plants including ferns, find some samples of ferns or moss that grow near you. Notice what the soil was like where you found them. What else was growing nearby?