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
Coal in Australia of production was exported (389 Mt out of 503 Mt total). Coal mining in Australia has been criticized by members of the environmental movement, due to carbon dioxide emissions during combustion. This criticism is primarily directed at thermal coal, for its connection to coal-fired power stations as a major source of carbon dioxide emissions, and the link to climate change and the effects of global warming on Australia. The burning of coal for electricity produces 29% of Australia's total greenhouse gas emissions, based on 2013-2014 Clean Energy Regulator data. The Carbon Pollution Reduction Scheme, which followed the draft report in