Coal

Coal (IPA: /ˈkəʊl/) is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. Coal is a readily combustible black or brownish-black rock. It is a sedimentary rock, but the harder forms, such as anthracite coal, can be regarded as metamorphic rocks because of later exposure to elevated temperature and pressure. It is composed primarily of carbon along with assorted other elements, including sulfur. It is the largest single source of fuel for the generation of electricity world-wide, as well as one of the largest sources of carbon dioxide emissions, which is considered the primary cause of global warming. Coal is extracted from the ground by coal mining, either underground mining or open pit mining (surface mining).