Scott Lovelace, age 14, of Richmond, Va., for his question:
HOW IS COAL FORMED?
Coal is a very important product that touches all of our lives even those of us who don't use it directly to heat our homes. Coal is used to produce electricity and smelt ore. Thousands of useful byproducts also come from coal, including nylon, paints, perfumes, water softeners, fertilizers, explosives, textiles, medicines, road tar, dyes and insect killers.
It literally took millions of years to form coal. It started, in fact, about 250 million years ago, long before man or dinosaurs walked on earth.
In those early days the land was low, flat and swampy. Ferns and plants grew lushly to more than 100 feet in height. As they died, they fell into the water and collected on the swamp bottoms. They didn't rot because they were sealed off by swamp water from oxygen in the air. The plants formed a thick layer of half rotted jellylike sludge called peat.
In time, water from the sea flowed over the swamps, carrying mud with it. Then the sea drained away again leaving more swampy lowlands. More ferns and plants flourished, then died and fell into the swamps.
As the millions of years passed, layers of vegetation lay deep in the earth's crust. Over them lay tons of earth and rock, pressing down and holding them in great heat and pressure. Slowly the ancient swamp mud turned into shale and sandstone while the long dead plants were pressed and heated until they hardened into the product we know today as coal.
Many fossils of leave can be found in coal. At times even whole tree trunks of coal have been discovered.
Geologists report that coal is actually a type of sedimentary rock.
Anthracite is the oldest type of coal and also the hardest. It is nearly all carbon and burns with a smokeless flame. Bituminous, or soft, coal makes up about 90 percent of coal mined today. About 50 percent of it is carbon with the rest of its mass being mostly volatile carbon compounds. The youngest coal is called lignite, and it is nearly 50 percent moisture.
Peat, which is in the coal family, is made up of 80 percent water. It is used as fuel in some countries. It is made of partly decayed moss.
Coal, by the way, is taken from the earth in either shaft mines or strip mines. In strip mining, layers of the coal are very close to the surface of the ground. It is necessary to go much deeper in some areas and then shaft mining with a deep hole and tunnels is the only way to harvest the coal.