Coal the heat and pressure of deep burial causes the loss of water, methane and carbon dioxide and an increase in the proportion of carbon. Thus first lignite (also called "brown coal"), then sub-bituminous coal, bituminous coal, and lastly anthracite (also called "hard coal" or "black coal") may be formed. The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, although coal is known from most geological periods. The exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants—this coal is presumed to
Burns Bog salmon-bearing creeks. Burns Bog is also a major carbon sink. Since organic matter decomposes at a very slow rate in the bog, carbon stays in the bog. High acidity and the waterlogged conditions of peatlands such as Burns Bog prevent complete decomposition of fixed carbon. This prevents the carbon from escaping into the atmosphere. European scientists state that an area of peatland the size of a soccer field stores as much carbon as driving a family car around the world three times. Burns Bog was formed at the end of the last ice age, which was 10,000 years ago. At