When the figure is not level people cannot know what is meant by width, depth, or height without being told (or without labels), although length is generally still assumed to mean the direction in which the figure is longest..
The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.oal is primarily used as a solid fuel to produce electricity and heat through combustion. World coal consumption was about 7.25 billion tonnes in 2010 (7.99 billion short tons) and is expected to increase 48% to 9.05 billion tonnes (9.98 billion short tons) by 2030.
Coal is a combustible rock and along with oil and natural gas it is one of the three most important fossil fuels. Coal has a wide range of uses; the most important use is for the generation of electricity. Coal forms from the accumulation of plant debris, usually in a swamp environment.When plant debris dies and falls into the swamp the standing water of the swamp protects it from decay. Swamp waters are usually deficient in oxygen, which would react with the plant debris and cause it to decay.oal is also used as a power source for factories. There it is used to heat steam and the steam is used to drive mechanical devices. A few decades ago most coal was used for space heating. Some coal is still used that way but other fuels and coal-produced electricity are now used instead.