Encyclopedia of Global Resources part 25 pot

Manning, D. A. C. Introduction to Industrial Minerals. New York: Chapman & Hall, 1995. Meunier, Alain. Clays. Translated by Nathalie Fradin. New York: Springer, 2005. Murray, Haydn H. Applied ClayMineralogy:Occurrences, Processing, and Application of Kaolins, Bentonites, Palygorskite-Sepiolite, and Common Clays. Boston: Elsevier, 2007. Newman, A. C. D., ed. Chemistry of Clays and Clay Min- erals. Harlow, England: Longman for Mineralogi- cal Society, 1986. Web Sites Natural Resources Canada Canadian Minerals Yearbook, Mineral and Metal Commodity Reviews http://www.nrcan-rncan.gc.ca/mms-smm/busi- indu/cmy-amc/com-eng.htm U.S. Geological Survey Clays: Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/clays See also: Ceramics; Chlorites; Open-pit mining; Pa- per; Residual mineral deposits; Sedimentary pro- cesses, rocks, and mineral deposits; Silicates; United States. Clean Air Act Categories: Laws and conventions; government and resources Dates: 1963, rewritten in 1970, amended in later years The Clean Air Acts of 1963 and 1970, with subse- quent amendments, are intended to improve air qual- ity in the United States, largely through mandated air quality standards. Background The 1963 Clean Air Act (CAA) and its 1965 amend- ments attempted to improve air quality in the United States through federal support of air pollution re- search and aid to states in establishing air pollution control agencies. The 1970 CAA provided for national air-quality standards by specifying maximum permissi - ble ambient air concentrations for pollutantsdeemed harmful to human health and the environment. The deadline for the enforcement of the primary stan- dards was set for 1982 but was later extended. Provisions The CAA provided that the Environmental Protec- tion Agency (EPA), established in 1970, was to set pol - lution standards for new plants and that states were to create state implementation plans for enforcement. 210 • Clean Air Act Global Resources Time Line of U.S. Clean Air Acts Year Law Provisions 1955 Air Pollution Control Act First U.S. law addressing air pollution and funding research into pollution prevention. 1963 Clean Air Act of 1963 First U.S. law providing for monitoring and control of air pollution. 1967 Air Quality Act Established enforcement provisions to reduce interstate air pollution transport. 1970 Clean Air Act Extension of 1970 Established first comprehensive emission regulatory structure, including the National Ambient Air Quality Standards (NAAQS). 1977 Clean Air Act Amendment of 1977 Provided for the prevention of deterioration in air quality in areas that were in compliance with the NAAQS. 1990 Clean Air Act Amendment of 1990 Established programs to control acid precipitation, as well as 189 specific toxic pollutants. Source: U.S. Environmental Protection Agency. The country was divided into 247 Air Quality Control Regions for enforcement purposes. Finally, the CAA mandated pollution standards for automobiles and trucks with specified deadlines for achievement; Con- gress, however, repeatedly waived the deadlines. The 1970 CAA and the 1977 amendments have been suc- cessful in reducing several ambient air pollutants, most notably carbon monoxide, lead, and suspended particulates. However, ozone, nitrogen dioxide, vola- tile organic compounds, and sulfur dioxide remain at high levels in many areas. The 1990 amendments to the CAA were so far- ranging as to constitute a rewriting of the act. The 1990 amendments displayed an awareness of develop- ing problems such as acid deposition and strato- spheric ozone (Titles IV and VI). Title I provided a new enforcement scheme with specific categories for cities (Los Angeles is in a category by itself) for reach- ing pollution standards for ozone, carbon monoxide, and particulates, with a twenty-year deadline for com- pliance. Title II provided specific standards for mo- bile source pollution with deadlines for compliance. Title III established emission limits for hazardous or toxic air pollutants with numerous deadlines for en- forcement. An innovative aspect of Title IV was the es- tablishment of aprocess of emissionstrading whereby the most polluting utilities could acquire the excess pollution capacity of less-polluting utilities. The goal was to reduce progressively the total amount of sulfur dioxide emitted in the United States through the op- eration of market forces. Impact on Resource Use The CAA has been explicitly directed toward improv- ing human health. Implicit in the CAA is a concern for the environment and the impact of air pollution on natural resources. Efforts to deal with acid deposi- tion, for example, display a concern for the impact of sulfur dioxide on water and forest products. The im- plementation of automobile emission standards has had a positive effect on oil consumption. The overall thrust of the Clean Air Act has been “technology-forcing”; in other words, industries have been forced to develop improved technologies to meet mandated standards. The results of this ap- proach have been mixed in urban areas. Some im- provement in air quality has certainly occurred. Nonetheless, costs have escalated for full achieve - ment of the various standards of the CAA. John M. Theilmann See also: Acid precipitation; Air pollution and air pollution control; Environmental Protection Agency; Ozone layer and ozone hole debate. Clean Water Act Categories: Laws and conventions; government and resources Date: Signed October 2, 1965 The Federal Water Quality Act of 1965, commonly known as the Clean Water Act, required states to set quality standards based on a waterway’s usage. It proved to be a crucial step in the protection of the coun- try’s water supply. Background “No one has a right to use America’s rivers and Amer- ica’s waterways, that belong to all the people, as a sewer.” With those words, President Lyndon Johnson signed the Federal Water Quality Act of 1965 and placed in motion steps to curtail pollution of the na- tion’swater. The fight to stopwater pollutionbegan in colonial times, when local laws prohibited dumping in major waterways. However, a national water policy was lacking until passage of the 1948 Federal Water Pollution Control Act. Concerned with the health ef- fects of water pollution, the law allowed legal inter- vention against polluters and provided funding for the development of sewage-treatment plants. Despite subsequent amendments furthering its cause, this act failed to provide a strong defense against polluters. In a February 8, 1965, speech, President Johnson stated, “Every major river and waterway is now pol- luted,” and he implored the nation to stop the de- struction. Pollution stemmed from municipal waste, industrial waste, and runoff from agricultural land. Each contained a wide variety of polluting agents and contributed to a massive problem that some feared would eventually contaminate the country’s entire water supply. Provisions The Federal Water Quality Act, or Clean Water Act, provided guidelines by which states could fight water pollution. First, states were to define each waterway, in whole or in part, by its dominant usage: water sup - ply, recreational, industrial, fish and wildlife propaga - Global Resources Clean Water Act • 211 tion, or agricultural. Second, states were to set water quality standards based on that primary usage. If states failed to comply by June 30, 1967, or set inade- quate standards, the Department of Health, Educa- tion, and Welfare (HEW) would berequired to set the quality standard. The hope was to prevent pollution before it occurred. The standards could be used to support legal actions against municipal, industrial, or individual offenders. The act also created the Water Pollution Control Administration under HEW, which was to have responsibility for enforcing the act. Even- tually water quality came under Environmental Pro- tection Agency control. Impact on Resource Use In 1970, the1948 and 1965acts were combined to cre- ate a strong national water policy. Further amended in 1972, this policy called for stricter standards and heightened enforcement tomake all navigable waters fishable and swimmable by 1983. Although that dead- line was subsequently abandoned, keeping water clean enough to meet the fishable and swimmable stan- dards remained the national goal. As water testing technology improved, the Clean Water Act (as all water quality-related acts have collectively been called beginning in 1972) strengthened the guidelines for water purity and protection. These acts were success- ful in reducing and eliminating contaminants in the nation’s water resources. Jennifer Davis See also: Clean Air Act; Environmental Protection Agency; Thermal pollution and thermal pollution control;Waterpollution andwater pollutioncontrol. Clear-cutting Category: Obtaining and using resources At one time a standard practice in lumbering, clear- cutting has become one of the most controversial har- vesting techniques used in modern logging. Definition Clear-cutting is the practice of cutting all the trees on a tract of land at the same time. A tract that has been clear-cut will haveno trees leftstanding. With its wind - rows of slash (the unmarketable portions of the tree, such as tops and branches) and debris, a clear-cut tract of land may appear to the untrained eye as though a catastrophic event has devastated the land- scape. As far as critics of clear-cutting are concerned, that is indeed what has happened. Overview The commercial forest industry is frequently de- nounced for damaging the environment through clear-cutting, particularly when clear-cutting is used to harvest timber on a large scale. Clear-cutting steep hillsides can leave the land susceptible to erosion, as the removal of all trees leaves nothing to slow the flow of rainfall. Clear-cut hillsides can lose topsoil at a rapid rate, choking nearby streams with sedimenta- tion and killing aquatic species, such as trout and sal- mon. The large amounts of slash or debris left behind can pose a fire hazard. Wildlife studies have also indi- cated that certain species of birds and mammals are threatened when their habitats are clear cut, as they either lose their nesting area or are exposed to in- creased risk from predators. The northern spotted owl, for example, becomes easy prey for great horned owls when it is forced to fly across large open areas. Representatives of the timber industry counter such criticisms by noting that, for some species of trees, selective harvesting simply does not work. Many species of trees will not regenerate in shaded areas. In addition, selective harvesting, or cutting only a lim- ited number of trees from a stand,can also be ecologi- cally damaging. Logging may create stress on the re- sidual standing timber, leading to disease and die-off of the uncut trees, while the operation of mechanized equipment can be as disrupting to nesting and forag- ing habits of wildlife as clear-cutting the stand would have been. Loggers further argue that criticisms of clear-cut- ting are often based on irrational considerations such as aesthetics—the public dislikes clear-cuts because they are ugly—rather than on sound silvicultural or ecological principles. Nonetheless, in many areas the timber industry has modified harvesting practices in response to public pressures and government con- cerns. Rather than clearing tracts of land in large rect- angular blocks,many woodsworkers nowcut offirreg- ularly shaped strips that are considerably smaller in size than before. Patchesof standing timber are left in clear-cut areas to provide cover for wildlife, and slash is chipped and spread as mulch to reduce the risk of brush fires.Buffer zones, or strips ofuncut timber, are 212 • Clear-cutting Global Resources left along stream banks and near lakes to slow or pre- vent runoff from the clear-cut areas. Clear-cutting re- mains an appropriate harvesting method in certain situations, as in cutting even-age stands of plantation- grown trees, but modifications in its application can help prevent damage to the environment. Nancy Farm Männikkö See also: Forest management; Forestry; Forests; Tim- ber industry; Wood and timber. Climate and resources Categories: Ecological resources; environment, conservation, and resource management Climate is the average of weather conditions at a place or in a region, usually recorded as both the mean(aver - age) and the extremes of temperature, precipitation, and other relevant conditions. Resources are the fac - tors and characteristics of the natural environment that people find useful, including climate, land, soil, water, minerals, and wild vegetation. Thus, climate is itself a natural resource, andit interacts withor affects the character or quality of other resources and their ex- ploitation or development. Background Climate can be seen as the most basic or primary of natural resources in that it affects other resources to a greater degree thanit is affected bythem. Perhaps the best evidence of this is in the nature and distribution of wildvegetation. (The term “wild vegetation”is pref- erable to “natural vegetation” because humankind has had dramatic impacts upon the character and dis- tribution of plants.) Temperature, moisture, and so- lar radiation are the major factors determining the plant species that will grow in a region, and the major global vegetation types (forest, shrub, grassland, desert, andtundra) reflect climatic controls. Microcli - mates are in turn created within the vegetation: trees provide shade and thus a slightly cooler temperature Global Resources Climate and resources • 213 A clear-cut mountainside in Canada. (©Charles Dyer/Dreamstime.com) than in the surrounding region. However, microcli - mates exist only inminuscule portions of the main cli- matic region; consequently, climate influences vege- tation more than the reverse. Solar radiation is the source of energy that drives the Earth’s atmosphere and its circulation system; therefore itis the basicelement in determining differ- ences in climate. The sun’s rays are vertical at some time of the year only in the tropics, between the Tropic of Cancer (23.5° north latitude) and the Tropic of Capricorn (23.5°south latitude).These linesdeter- mine where the greatest heat supply is found; regions poleward of about 40° north and south latitudes actu- ally have a net loss of reradiation to outer space and depend upon a heat supply from the tropics, which is carried poleward by the general circulation of the atmosphere. Equatorial Climates The general circulation is the average of wind flow at the surface of the Earth and is drivenby the surplus of solar radiation in the tropics. By definition, tropical climates do not experience freezing temperatures, have the least variation in length of day, and conse- quently experience the least “seasonality” of any lati- tudes. Seasons here are characterizedmore by precip- itation contrasts—“dry” and “wet”—rather than by summer and winter temperatures. The greatest com- bination of heat and moisture resources on the Earth’s surface, especially important in creating the condi- tions under which the tropical rain forest flourishes, is near the equator. Rates of weathering of bedrock and soils are great- est in the equatorial region, because weathering is a function of theavailability of heat and moisture. It fol- lows that the depth to which rock and soils are weath- ered and leached (mineral plant foods dissolved and removed by groundwater flow) is greater here than elsewhere on the Earth’s surface. Continuous high temperatures work against carbon storage in thesoils; organic carbon storage requires recycling from wild vegetation. Oxidation of organic matter by exposure to thesun’srays followsthe clearingof tropical forests. Under wild vegetation conditions, where the rain for- est canopy protects soils from raindrop impact, ero- sion rates are not as high as one would expect from the intense rain showers. However, on sloping land, the soils become saturated and flow downslope, often catastrophically in disastrous landslides. Where wild vegetation has been removed by human activity, in farming or especially in urban centers, erosion and mass wasting (landslides) are exacerbated during rainy seasons and cause considerable loss of life and property damage. With increasing distance from the equator, the trop- ics experience more pronounced seasons, particularly in moisture resources. Precipitation totals decline, and drought risk increases. Dry seasons are expected annu- ally because of the shifting of the general circulation of the atmosphere. The timing and extent of this shift determine whether a region experiences drought (a period when significantly lower-than-average precipi- tation causes low levels of streamflow and increased stress on vegetation, both wild and cultivated). East and South Asia are most affected by shifting atmo- spheric circulation and the resultant wet and dry sea- sons, or “monsoons.” Africa also has pronounced wet and dry seasons as a result of shifting atmospheric cir- culation patterns; droughts in the Sahel and East Af- rica are a consequence of the failure of rains to reach the region in time to support agriculture and grazing. Droughts in this part of the world result in famine: An estimated one million persons died in the Sahelian droughts of the late 1960’s and 1970’s. Thus climate must be defined in terms of both averages and ex- tremes; the latter result in hazards that have dire con- sequences for the inhabitants of the affected region. The probability of a drought hazard occurring in- creases as precipitation averages decrease (an inverse relationship) and is exacerbated by the fact that most tropical rainfall falls as intense thundershowers, which are spatially highly variable. One farm may be drenched by rain while its neighbors continue to be tormented by drought. In addition to drought risk on the margins of the tropics, the major climatic hazard is the tropical cyclone, which goes by various names, most commonly hurricane or typhoon. These cy- clones, too, rarely affect the equatorial zone but fre- quent the tropical transition to the subtropics and midlatitudes. Movement of tropical cyclones is east- erly in their early and middle stages, following the general circulation known as the trade winds. The Subtropics The typesof climatesthat existpoleward ofthe tropics depend on the side of the continent: West sides are deserts or drylands; east sides are the humid subtrop- ics, a transition zone with cooler temperatures and more risk of frost with greater distance from the equa - tor. The humid subtropics are also subject to occa - 214 • Climate and resources Global Resources sional easterly flow weather systems, including tropi - cal cyclones. While they represent a serious hazard, claiming both lives and property, these easterly sys- tems also deliver moisture and thus reduce the possi- bility of drought. The generally warm temperatures and moist conditionsmake these climatessome of the most productive for crop growth, even exceeding the potential of the tropics. Leaching of soils and high erosion rates on cleared fields are nearly as great a problem as in the tropics, as is the rapid rate of or- ganic decomposition. The west coast drylands, which include all the world’s major deserts—Sahara, Atacama, Kalahari, Australian, and North American—are a consequence of the general circulation of the atmosphere, which chooses these locations to make the swing from the prevailing westerlies of the middle latitudes to the easterly trade winds. In the process, high atmospheric pressures prevail, andwinds are descending or subsid- ing, and therefore warming—just the opposite of the conditions required for rainfall. The drylands mayex- tend deep into the continents, as in North America and especially in Africa and Asia; the dryness of the Sahara also blankets the Middle East and extends northward into Central Asia. Temperatures along the equatorward flank of these five major dryland zones are tropical, and where irrigation water is available, tropical plantsmay begrown. Mostof thedrylands are subtropical or midlatitude, and thus they experience frost as well as drought hazard. Weathering and ero- sion are appreciably less in the drylands, owing to the absence of moisture, and leaching of the soils is virtu- ally absent. Instead, salts in the soils can build up to levels that are toxic to most plants—another climate- related hazard. The Midlatitudes The midlatitudes extend from the subtropics to the polar climates of the Arctic and Antarctic, with tem- peratures following a transition from warm on the equatorward flank to too cold for agriculture nearer the poles. This is the realm of the westerlies, with extratropical cyclones delivering most of the weather. It is a zone of contrasting conditions, year-by-year and day-by-day, ranging from warmer than average to colder than average, from too humid to too dry on the inland dryland border. Thus the hazards of extremes of temperature and precipitation often dominate life, as tropical and po - lar air masses converge to create the cyclones that march from west to east. Drought risk is most impor - tant on the dryland border and results in the world’s great grasslands. Summerheat may be a hazard on oc- casion, and nearly every winter brings storms with freezing rain, high winds, and heavy snowfalls, partic- ularly on the eastern sides of the continents. The east- ern sides are also afflicted with such intense summer storms as the tornadoes of North America (a winter phenomenon in the adjoining humid subtropics), and the tail end of hurricanes and typhoons, as these become caught up in westerly circulation and curve poleward again. The Arctic fringe of the midlatitudes is too cool for significant agriculture but yields the great subarctic forests of Canada, Scandinavia, and Russia. Polar climates are too cold for all but a few hunters and fishers and people engaged in extractive industries or scientific research. Neil E. Salisbury Further Reading Anderson, Bruce T., and Alan Strahler. Visualizing Weather and Climate. Hoboken, N.J.: Wiley, in col- laboration with the National Geographic Society, 2008. Bryson, Reid A., and Thomas J. Murray. Climates of Hunger: Mankind and the World’s Changing Weather. Madison: University of Wisconsin Press, 1977. Grigg, D.B. The AgriculturalSystems of the World: AnEvo- lutionary Approach. New York: Cambridge Univer- sity Press, 1974. Le Roy Ladurie, Emmanuel. Times of Feast, Times of Famine: A History of Climate Since the Year 1000. Rev. and updated ed. Translated by Barbara Bray. New York: Noonday Press, 1988. Ruddiman, William F. Plows, Plagues, and Petroleum: How HumansTook Controlof Climate. Princeton,N.J.: Princeton University Press, 2005. Sivakumar, Mannava V. K., and Raymond P. Motha, eds. Managing Weather and Climate Risks in Agricul- ture. New York: Springer, 2007. Strahler, Alan H., and Arthur N. Strahler. Introducing Physical Geography. 4th ed. Hoboken, N.J.: J. Wiley, 2006. Strahler, Arthur N., and Alan H. Strahler. Elements of Physical Geography. 4th ed. New York: Wiley, 1989. See also: Agriculture industry; Atmosphere; Deserti- fication; Deserts; Drought; Dust Bowl; El Niño and La Niña; Forests; Grasslands; Monsoons; Rain forests; Weather and resources. Global Resources Climate and resources • 215 Climate change. See Greenhouse gases and global climate change Climate Change and Sustainable Energy Act Categories: Laws and conventions; government and resources Date: June 21, 2006 In the later part of the twentieth century and the early part of the twenty-first century, global temperatures have been some of the warmest ever recorded. Measures to reduce greenhouse gases and the implementation of alternative sources of renewable energy are ways of combating climate change. The United Kingdom’s Climate Change and Sustainable Energy Act 2006 promotes microgeneration technologies to replace car- bon-based fuel sources. Background Countries in the developed world have established initiatives to reduce greenhouse gases and combat climate change. Common greenhouse gases include carbon dioxide, methane, nitrous oxide, and hydro- fluorocarbons. Greenhouse gases act to absorb the Earth’s infrared radiation and increase temperatures. The Kyoto Protocol, an important climate-change measure ratified by many industrialized countries, was established in 1997. Some countries establish their own greenhouse-gas emission standards. For exam- ple, the United Kingdom enacted the Sustainable En- ergy Act of 2003 and the Energy Act of2004; modifica- tions of microgeneration targets were applied to the 2006 act. The Climate Change and Sustainable En- ergy Act is a law that builds upon previous climate change policies. Provisions The Climate Change and Sustainable Energy Act was enacted on June 21, 2006, in an effort to encourage microgeneration technologies aimed at reducing greenhouse-gas emissions. Microgeneration technol- ogies include many non-carbon-fueledenergy sources. Microgeneration is the generation of electricity and heat from a renewable energy source. These sources include non-fossil fuels and nonnuclear fuels, such as biomass, biofuel, wind, water-tide, solar-power, and geothermal sources. All renewable sources of fuel are useful in microgeneration. This initiative of increas- ing microgeneration technologies ultimately will re- duce dependency on carbon-based energy emissions. The Climate Change and Sustainable Energy Act per- mits homes to reduce dependency on carbon-based fuel sources and increase microgeneration technolo- gies. Building-construction regulations are also speci- fied in this act. Each year, the ministerial authorities report to Parliament the measures taken by the gov- ernment in support of this measure. Local authorities have access to the reports and ensure that these mea- sures are followed at the local level. This act incen- tivizes local governments to encourage the use of microgeneration and the reduction of greenhouse- gas emissions. Impact on Resource Use A 2009 assessment by the U.S. Global Change Re- search Program outlined the effect of the increase in greenhouse gases. The increase of global tempera- tures could be as high as 6° Celsius by the year 2090, suggesting that climate change is real and has dra- matic impacts. By the end of the twenty-first cen- tury, sea levels in U.S. coastal regions may rise more than 1 meter. Climate change has occurred even more rapidly in the Arctic regions, where ice is melt- ing, and the fishing industry may experience a nega- tive impact. The Climate Change and Sustainable Energy Act serves as a model for other industrialized countries. For example, Germany is combating climate change with asimilarlaw: theRenewable EnergySources Act. Kevin D. Weakley Web Site Climate Change and Sustainable Energy Act, 2006 http://www.opsi.gov.uk/acts/acts2006/pdf/ ukpga_20060019_en.pdf See also: Agenda 21; Climate and resources; Earth Summit; Gore, Al; Greenhouse gases and global cli- mate change; Kyoto Protocol. 216 • Climate Change and Sustainable Energy Act Global Resources Coal Category: Energy resources Where Found While coal has been found on every principal conti- nent of the Earth, regional distribution is restricted to sedimentary and metamorphosed sedimentary rock terrains of Upper Devonian age and younger (that is, the last 365 million years of geologic history). As a result of this geologic association, most of the coal re- serves of the world are found in the Northern Hemi- sphere continents of Asia, Europe, and North Amer- ica. However, there are reasonably large reserves in Australia, South Africa, and Colombia. Primary Uses Coal was historically used as a domestic fuel for the heating of homes, and more than 26 percent of the coal mined globally is a primary source of energy. Worldwide, 41 percent of coal mined is burned in power plants, principally for the generation of elec- tricity. Another significant use is in the manufacture of coke, an improved carbon-content derivative of coal employed in the production of steel. Lesser amounts of coal are used in the direct heating of homes, for a variety of industrial purposes, and, in- creasingly, in liquefaction and gasification processes whereby coal is converted to liquid andgaseous forms of hydrocarbon fuels. Technical Definition Coal is a general term encompassing a variety of com- bustible sedimentary and metamorphic rocks con- taining altered and fossilized terrestrial plant remains in excess of 50 percent by weight and more than 70 percent by volume.Categories ofcoal differ inrelative amounts ofmoisture, volatile matter, fixed carbon,and degree of compaction of the original carbonaceous material. Coal is commonly termed a fossil fuel. Cate- gories of coal include peat (a coal precursor), lignite, bituminous coal,subbituminouscoal, andanthracite. Peat. Peat, an unconsolidated accumulation of partly decomposed plant material, has an approxi- mate carbon content of 20 percent. Inmany classifica- tion schemes, peat is listed as the initial stage of coal formation. Moisture content is quite high, at least at the 75 percent level. When dry, peat has an oxygen content of about 30 percent, is flammable, and will freely but inefficiently burn slowly and steadily for months at a low-heat-content value of 5,400 British thermal units (Btus) per pound. Lignite. Lignite, or brown coal, is brownish-black in color,banded and jointed,and subject tospontane- ous combustion.Carbon contentranges from25 to35 percent. With a moisture content around 40 percent, it will readily disintegrate after drying in the open air. Because lignite has a maximum calorific value of 8,300 Btus, it is classed as a low-heating-value coal. Bituminous coal. Deeper burialwith even higher temperatures and pressures gradually transforms lig- nite into bituminous coal, a dense, dusty, brittle, well- jointed, dark brown to black fuel that burns readily with a smoky yellow flame. Calorificvalue ranges from 10,500 to 15,500 Btus per pound, and carbon content varies from 45 to 86 percent. Moisture content is as low as 5 percent, but heating value is high. Subbituminous Coal. The subbituminous class of coal is intermediate between lignite and bituminous and has characteristics of both. Little woody matter is visible. It splits parallel to bedding but generally lacks the jointing of bituminous coal. It burns clean but with a relatively low heating value. Anthracite. Anthracite is jet black in color, has a high luster,is very hard and dust free,and breaks witha conchoidal fracture. Carboncontent rangesfrom 86to 98 percent. It is slow to ignite; burns with a short blue flame without smoke; and, with a calorific value in ex- cess of14,000Btus perpound, isa highheating fuel. Description, Distribution, and Forms Coal isafossil fuelfound onall sevencontinents andis in commercial production on all but the continent of Antarctica. The top-ten producers of coal in 2008 were China, the United States, Australia, India, South Africa, Russia, Indonesia, Poland, Kazakhstan, and Colombia. In 1992, a reserve of more than 185 billion metric tons of lignite was discovered in Pakistan, but the cost of production and lack of infrastructure have prevented development or accurate analysis of the field. The quantitative distribution of coal is more diffi- cult to determine than its geographicdistribution. Es- timates indicate that total world coal resources, de- fined as coal reserves and other deposits that are not economically recoverable plus inferred future discov- eries, are on the order of 9 trillion metric tons and ex - ist in every country. Of this amount, estimates of world coal reserves, defined as those deposits that Global Resources Coal • 217 have been measured, evaluated, and can be extracted profitably under existing technologic and economic conditions, are approximately 900 billion metric tons and are found in about seventy countries. If the latter figure isaccepted asreasonable, worldreserves canbe divided into two categories, with about three-quarters composed of anthracite and bituminous coals and about one-quarter composed of lignite. When the lig- nite reserves in Pakistan can be reliably analyzed, these figures will change. On a country-to-country comparison, the United States possesses the greatest amount of total world coal reserves. Geographic distribution in the United States is divided into five coal provinces, incorporat- ing at least thirty-three states. These are termed the Appalachian or Eastern, the Interior, the Gulf, the Rocky Mountain, and the Northern Great Plains coal provinces. The Eastern (Appalachian) province, stretching along the flanks of the Appalachian Mountains from northern Pennsylvania into central Georgia, contains approximately 40 percent of the bituminous coal re- serves of the United States as well as the principal re- serve ofanthracite rank coal on the continent. Within the Interior province, bituminous coals are divided among the Michigan, Illinois, and Western Interior 218 • Coal Global Resources Data from British Petroleum, .Source: Statistical Review of Energy, 2009 152,800,000 141,100,000 141,100,000 60,500,000 58,800,000 47,800,000 47,700,000 40,200,000 36,000,000 Metric Tons 1,500,000,0001,250,000,0001,000,000,000750,000,000500,000,000250,000,000 Ukraine Kazakhstan Poland South Africa Indonesia Russia Colombia Germany Canada India Australia United States China 194,300,000 219,900,000 596,900,000 1,414,500,000 Coal: Top World Producers, 2008 basins, the latter located in Iowa, Missouri, Kansas, and Oklahoma. Lignite is the chief coal found in the Gulf province, situated in Mississippi, northern Loui- siana, and coastal Texas. Rocky Mountain bituminous and subbituminousdeposits are scattered throughout at least five states from Wyoming south into Arizona and New Mexico. Lignite and bituminous coals con- stitute the Northern Great Plains province of Mon- tana and portions of North and South Dakota. Coal is mined in twenty-five states, but ten states alone contain 90 percent of the total U.S. reserves. These are, in order of increasing reserve tonnage, In- diana, Texas, Colorado, Ohio, Kentucky, Pennsylva- nia, West Virginia, Wyoming, Illinois, and Montana. Montana contains a full 25 percent of U.S. coal re- serves. Small reserves of relatively low-grade coal are known in the Pacific Northwest region. Significant amounts of coal have been discovered in Alaska, but difficulty in mining and great distance to markets cause these deposits to be classedas resourcesand not economic reserves. Following the United States, the countries with the largest coal reserves are Russia, China, India, Austra- lia, and South Africa. Estimates indicate that global coal reserves will last some 130 to 150 years at current production levels, although by some methods of cal- culation that period is significantly shorter. The more common and ordinary coals are of vas- cular vegetable origin, formed from the compaction and induration of accumulated remains of plants that once grew in extensive swamp and coastal marsh ar- eas. These deposits are classed as humic coals consist- ing of organic matter that has passed through the peat, or earliest coal formation, stage. A variety of humic coals are known. The swamp-water environment in which humic coals form must be deficient in dissolved oxygen, the Global Resources Coal • 219 Data from U.S. Mining Association (converted from short tons).Source: 29.4 31.7 104.6 39.4 26.8 59 38 139 411 Million Metric Tons 500400300200100 West Virginia North Dakota Montana Kentucky Indiana Illinois Pennsylvania Texas Wyoming Colorado 33 Leading U.S. Coal-Producing States, 2007 . conventions; government and resources Date: June 21, 2006 In the later part of the twentieth century and the early part of the twenty-first century, global temperatures have been some of the warmest ever. the heating of homes, and more than 26 percent of the coal mined globally is a primary source of energy. Worldwide, 41 percent of coal mined is burned in power plants, principally for the generation of. manufacture of coke, an improved carbon-content derivative of coal employed in the production of steel. Lesser amounts of coal are used in the direct heating of homes, for a variety of industrial