coal

Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata [stratum(层)的复数] called coal seams [层]. Coal is mostly carbon with variable amounts of other elements; chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dead plant matter decays into peat [泥煤] and is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits of coal originate in former wetlands - called coal forests - that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times. However, many significant coal deposits are younger than this and originate from the Mesozoic and Cenozoic eras. 晚石炭纪(宾夕法尼亚纪)和二叠纪。然而，许多重要的煤矿床比这更年轻，并且起源于中生代和新生代。新生代距今6500万年，是最新的一个地质时代。随着恐龙的灭绝，中生代结束，新生代开始。新生代分为古近纪、新近纪和第四纪。

The conversion of dead vegetation into coal is called coalification. At various times in the geologic past, the Earth had dense forests in low-lying wetland areas. In these wetlands, the process of coalification began when dead plant matter was protected from biodegradation and oxidation, usually by mud or acidic water, and was converted into peat. This trapped the carbon in immense peat bogs that were eventually deeply buried by sediments. Then, over millions of years, the heat and pressure of deep burial caused the loss of water, methane and carbon dioxide and increased in the proportion of carbon. The grade of coal produced depended on the maximum pressure and temperature reached, with lignite (also called "brown coal") produced under relatively mild conditions, and sub-bituminous coal, bituminous coal, or anthracite [亚烟煤、烟煤或无烟煤] (also called "hard coal" or "black coal") produced in turn with increasing temperature and pressure.

对于石油的形成原因，科学家目前也没有确定的答案，只是提出了两种可能的观点。一是来自西方国家的有机成因学说，另一个是源于前苏联的无机成因学说。

Coal is primarily used as a fuel. While coal has been known and used for thousands of years, its usage was limited prior to the Industrial Revolution. With the invention of the steam engine coal consumption increased. As of 2016, coal remains an important fuel as it supplied about a quarter of the world's primary energy and two-fifths of electricity. Some iron and steel making and other industrial processes burn coal.

The extraction and use of coal causes many premature deaths and much illness. The coal industry damages the environment, including by climate change as it is the largest anthropogenic [created by people or caused by human activity] source of carbon dioxide, 14.4 gigatonnes (Gt) in 2018, which is 40% of the total fossil fuel emissions and over 25% of total global greenhouse gas emissions.As part of the worldwide energy transition many countries have reduced or eliminated their use of coal power, and the UN Secretary General has asked governments to stop building new coal plants by 2020. Coal use peaked in 2013 but to meet the Paris Agreement target of keeping global warming to well below 2 °C (3.6 °F) coal use needs to halve from 2020 to 2030.

• anthropo- related to men or people.
• -ology any science or branch of knowledge
• Anthropology is the scientific study of people, society, and culture.

六级/考研单词: carbon, invariable, hydrogen, sulfur, oxygen, nitrogen, decay, convert, shallow, million, deposit, tropic, era, vegetation, dense, oxide, mud, trap, immense, dioxide, mild, usage, revolve, extract, premature, fossil, emit, globe, greenhouse, transition, eliminate