Earth resource patterns

The physical character and distribution of natural resources at the face of the Earth. No section of the Earth is exactly like any other in its resource endowment. Combinations of land and ocean, latitudinal differences in insolation, variations in receipt of precipitation, patterns of geology, and deformation of the Earth's crust all converge to create different resources in various regions of the world. Nevertheless, there is some repetition in these natural features and forces of nature across the Earth. These similarities that exist from place to place distinguish regional patterns in the availability of resources on a global scale.

Delineation of the Earth's resource patterns begins with differentiation between continental and marine resources. Although the resources of the oceans and seas have been used by people since earliest times, the more than 6,000,000,000 on the Earth today are primarily dependent upon the resources of the land for their existence.

Five principal resources associated with the land are soils, forests, grasslands, fresh-water resources, and minerals. Although other resources such as native animal life may be of local importance, and although the very concept of “resources” has been extended to include such complexes as recreation resources, these five land resources remain of fundamental importance for the material support of human life.

Natural resources include any substance or material, produced by natural forces within the Earth system, that is used or valued by humans. Some of these resources more quickly regenerate, and are naturally replaced after being extracted. These resources—forests, marine life, soil, fresh water, agricultural crops—are termed renewable resources (Figs. 1 and 2) and may be used indefinitely if rate of use is balanced with rate of regrowth or replenishment. Other resources cannot be regenerated so quickly and are steadily used up by humans. These nonrenewable resources include oil, natural gas, coal, and metals.

Two types of natural forces have converged to create the natural materials that are used and valued by humans. One set of forces consists of the basic climatic controls, including latitude, distribution of land and water, the wind and pressure system of the rotating Earth, the major landforms of the continents, and the elevation of the land surface above sea level. A second, independent set of forces consists of the tectonic and rock-forming processes which have operated over the Earth. The climatic controls account for variations in regional climates over the continents, and these climates in turn help to shape the the unique character of forests, grasslands, and fresh-water resources, as well as some of the fundamental attributes of soils and the agriculture they support. The second set of forces may be regarded as even more fundamental since the movements of the Earth's plates and their associated continents in conjunction with the Earth's plate tectonics account not only for the position on the Earth and hence the latitudinal location of each continent, but also for the global distribution of land and water and continental landforms, all with consequences for regional climatic patterns. Moreover, rock composition and surface configuration also influence the development of forests, grasslands, water resources, and soils which alter the patterns within the climatic regions, and surface and subsurface geology are fundamental to an understanding of the global patterns of minerals on and beneath the Earth's surface.

 

 

Fig. 1  Regions of selected primary and secondary industries.

بزرگنمایی تصویر

 

 

Fig. 2  Major agricultural regions

 

بزرگنمایی تصویر

 

Fig. 3  Predominant earth resource patterns. Climate types are identified as (1) polar and ice cap, (2) tundra, (3) taiga, (4) puna, (5) upper midlatitude, (6) humid subtropical, (7 and 8) wet-and-dry and rainforest, (9 and 10) desert and semiarid, (11) mediterranean. The map is a flat polar quartic equal-area projection.

 

بزرگنمایی تصویر

 

 

 

 

Climatic types

 

Because many resources reflect the climatic regime under which they form, it is important to understand distinctions between climates, where these various climates are found, and how climates influence the natural development of resources. World climates may be broadly classified in four types, which vary according to combinations of temperature and precipitation, and vary seasonally in both phenomena due to latitude and proximity to oceans or mountains (Fig. 3). Distinction is made between the so-called humid climates and the water-deficient climates, with subtypes as follows: 

Humid microthermal

1. Polar and ice cap

2. Tundra

3. Taiga

4. Puna

Humid mesothermal

5. Upper midlatitude

6. Humid subtropical

Humid macrothermal

7. Wet-and-dry

8. Rainforest

Water-deficient

9. Desert

10. Semiarid

11. Mediterranean

 

Humid microthermal regions

 

These areas of predominantly low temperature are so unfavorable to soil formation and use in agriculture that under present techniques their population-carrying capacity is low even in those regions with the warmest summers.

1. In polar and ice cap areas where soils and vegetative growth are essentially absent, available resources necessarily are dominantly marine and land animal life, on which the sparse native human settlement is almost wholly dependent. Despite the enormous size of the Antarctic, settlements are exclusively in the Arctic, except for special government-supported Antarctic stations.

2. Tundra, except for minor alpine locations, is entirely within the Northern Hemisphere. The principal renewable resources are lichens and the native animal life, such as reindeer and caribous, which can use these as food. Parts of the tundra may be considered a grazing land, as managed herds of reindeer are pastured nomadically. The natural resource significance of tundra lands for the larger world may be greatly enhanced locally where minerals are being extracted, such as the oil field adjacent to Prudhoe Bay on Alaska's North Slope.  See also: Tundra

3. Millions of acres of boreal coniferous forest, or taiga, located in a broad curving zone from Scandinavia across the northern, European part of Russia, and Siberia, and, east of the Bering Sea, across much of Alaska and northern Canada, has given its name to this climatic belt. Varieties of spruce, fir, and larch, which are of particular significance to the pulping industries, constitute the most valuable known renewable resource of the humid microthermal regions. The zone of taiga climate is of scant importance for agriculture; soils are predominantly thin, stony, and infertile, and development for agriculture is further discouraged by the possible incidence of frost in every month of the year and by the short growing season of 80 days or less. As in the case of the areas of tundra climate, the resource significance of particular localities within the taiga zone is locally enhanced by deposits of minerals; globally significant deposits of gold, silver, iron, lead, zinc, uranium, copper, and other metals are found in the taiga lands of Canada and Russia. Fresh-water resources are extensive, and some hydroelectric power is developed.  See also: Taiga

4. The puna type of climate is found at much lower latitudes but at elevations generally 10,000 ft (3048 m) or more above sea level, and is characteristically cold. Certain plateaus, particularly the high plateau of Tibet and the intermontane Andean plateau (Altiplano) of southeastern Peru and western Bolivia, belong to this group. Low temperatures preclude tree growth, and the principal renewable resource is low-productivity grazing land. Thin, stony soils are limited in production to hardy small grains and root crops. The resource significance of the South American puna is greatly enhanced by metal deposits, particularly those of copper, tin, lead, and zinc.  See also: Puna

 

Humid mesothermal regions

 

Considered in the light of present-day technology, the heart of the world's renewable natural resource base is in the humid mesothermal regions with their generally adequate precipitation and intermediate temperatures. These middle latitude regions of Earth contain a large share of the world's most productive soils which support both crop and pasture lands. Some productive coniferous and broad-leaf forests occur in these climatic regions. Concentrated surface and subsurface fresh-water supplies are relatively abundant, but owing to the high population densities and major urban and industrial complexes in these regions, the water resources are often intensively developed to the point where the quantity and quality of resources is diminished.

5. Upper midlatitude climate contains most of the lands adapted to the raising of wheat, barley, rye, and oats. In addition, certain areas within this climatic type, and particularly the North American corn belt and the Middle Danube Basin and the North Italian Plain, also produce maize. Further crops, including soybeans, are also important, and extensive forage cropping supports dairying and meat animal raising in east-central North America, western and central Europe, and the nonarid part of southern European Russia. The lands which support the agricultural types of this climatic region possess the most extensive areas of superior soils on Earth. They are relatively deep and are often moderately to highly endowed with plant nutrients and humus. Some of the best soils have developed from glacial drift; others have benefited from the deposition of fine-grained windblown loess deposits during the glacial period. Extensive preagricultural grasslands also contributed high humus content to some of the soils. Finally, the extensive plains under which these soils are deployed, and the generally favorable growing season conditions of temperature and rainfall, also underlie the present high productivity of the agriculture supported by the soils in this climatic type. It is within the upper midlatitude climate that the region of greatest surplus food production (the North American interior) exists.

6. Humid subtropical areas have an ample water supply and relatively long growing season (200 days or longer), making the best of these lands potentially very productive for crops or for forest products. Soils other than in floodplains tend to be less fertile than those of upper midlatitudes, however, owing to the effects of relatively high rainfall and temperatures on the removal of plant nutrients, and generally require fertilization for sustained cultivation over long periods. Where cropping is on alluvial soils of floodplains large and small, as in central and southern China and in southern Japan, and in the Ganges Plain of India, soils are more easily maintained at high levels of productivity. High rural population densities generally preclude the generation of large exportable food surpluses from regions with the best soils. Although the favorable combination of temperature and moisture can result in high timber growth, as on the best-managed tracts of forest in the American South, the potential is not realized in other areas of the Earth having this type of climate, owing to previous large-scale deforestation. Water resources are generally abundant; in part of southern and eastern Asia, fresh-water resources underlie the most extensive humid land irrigation in the world—namely, for paddy rice.

 

Humid macrothermal regions

 

These low latitude, predominantly winterless regions of warm to hot temperatures are divided according to the regime of rainfall:

7. Wet-and-dry, with a pronounced dry season, characterizes the tropical savanna regions of the Earth. These tall grasslands, mixed with scattered tropical trees, offer some of the most extensive grazing lands in Africa and northern Australia. Some of the savanna region, the original home of the big game herd animals in the African plains, is now used for commercial livestock and mixed farming.

8. Rainforest, with year-round growing seasons but over extensive areas their soils are lateritic with a high iron content, and harden irreparably under use for cropping. Problems induced by fungal growth, bacterial disease, and insect abundance also handicap the use of the soil resources. Within the great alluvial valleys, flooding may also be disruptive. Owing to these adverse factors, shifting cultivation is common, and much land is not in production at any particular time. Within the rainforest regions, extensive and rapid-growing forests occur, including the largest such forest area on the Earth in the Amazon Basin, but are mostly unexploited commercially in the twentieth-century economy. Extensive clearing of the Amazon forest for agricultural development appears likely during the last two decades of the twentieth century. Sites of enormous potential hydroelectric generation are largely undeveloped. Extensive iron and aluminum deposits have become concentrated within the rainforest soils after centuries of heavy rainfall has leached away most other soil substances. Many of these deposits have been exploited by domestic and multinational mining corporations.  See also: Rainforest

 

Water-deficient regions

 

Receipts of moisture are scant or lacking during much of the year. Except where exotic water supplies are available for irrigation, soils inherently are less productive than those of any humid region with comparable land surface. There are three major subdivisions.

9. Deserts differ strikingly in their form and in temperature conditions, but everywhere present meager resources for agriculture. Where water is available, desert oases blossom, but vast areas contain only scrub growth, ephemerals, or virtually no vegetation. Livestock-carrying capacity of desert scrub is meager, though all but the most extreme deserts have traditionally been occupied by groups of nomadic pastoralists who typically herd goats, sheep, or camels. Sparsity of vegetation has made mineral prospecting and exploration somewhat easier than in vegetation-covered humid areas, and in this century desert occupancy often started with mineral discoveries.  See also: Desert

10. The semiarid regions are basically grasslands, which have grazing as their characteristic resource use. Because of cyclic rainfall variability, people have converted the inherently fertile soils, as in China and the United States, to cereal growing during periods of higher rainfall. Rainfall fluctuations, however, make the soils unstable under cultivation. For this reason, these regions have suffered consistently from unsuited cultivation and overgrazing. Semiarid lands are responsive to and most productive under irrigation, but neither surface-water nor ground-water resources are adequate to irrigate more than a fraction of the area.  See also: Grassland ecosystem

11. Regions of mediterranean climate, because of their winter rainfall, generally are classed as humid lands. However, the greater part of the gowing season is water-deficient, and the most productive agricultural lands depend on irrigation. Soils are the major resource since water deficiency is pronounced enough to discourage forest productivity. Major mineral deposits may complement agricultural lands in a few areas.  See also: Climatology

 

 

Rock composition and surface configuration

 

Imposed on the basic resource pattern induced by climatic differences are variations in rock composition and surface configuration which cause intraregional differences within the patterns already described. Although not exactly the same in their effects, the variations caused by these two geographical elements are often concomitant and may be treated together as follows:

Rock composition and structure

Flat-lying and moderately folded sedimentary rocks

Igneous, metamorphic, strongly folded sedimentary rocks

Volcanic rocks

Surface configuration

Floodplains and other flat or gently sloped surfaces

Mountains and maturely dissected hill lands, plateau faces, of faces of cuestas

 

These elements of crustal variation produce the six following geographical differences in resource endowment:

First, all major agricultural lands are on flat-lying or moderately folded sediments and have gentle slopes, well exemplified in such alluvial valleys as the Mississippi, Nile, Huang, and Ganges-Brahmaputra, and such other outstanding agricultural areas as the North American corn belt or the Paris Basin.

Second, productive secondary agricultural lands, particularly in the tropics, are located on volcanic areas where soils have been formed through weathering or wind action. Examples include the Deccan Plateau in west-central peninsular India, and volcanic soils fringing much of the central mountain backbone of Java.

Third, agricultural lands are extremely limited on igneous rock areas, no matter what the surface configuration, in regions north of 40°N latitude, as illustrated in the Laurentian Shield area of Canada and the Fenno-Scandian Shield in northern Europe. In the humid tropical and subtropical climates, however, where weathering has proceeded long enough to produce a substantial soil mantle as on the Piedmont of the southeastern United States, underlying igneous rocks do not have the same negative effect on agricultural development.

Fourth, forest lands are not limited in their extent (although limited in productivity) by either crustal rock composition or surface configuration.

Fifth, mountains are important catchment areas and sources of fresh water and the services which may be derived from water. Most hydroelectric generation, or generation potential, is associated with mountains. In arid and semiarid regions, mountains are sources of water for irrigation, domestic and industrial supply, wood products, and warm-season grazing lands.

Sixth, mineral resources have definite patterns which are associated with rock structure and composition. Major deposits of coal and lignite, petroleum, and natural gas are, with few exceptions, found in flat-lying or gently folded and faulted sedimentary rocks, as in Texan oil fields and the coal fields of the Allegheny Plateau. Sedimentary nonmetallics (the phosphates, potash, sulfur, nitrates, and limestone) as well as bauxite and uranium (carnotite) also are associated with sedimentary rocks.

Associated with the igneous and metamorphic rock areas are most metals, for example, iron (usually), lead, copper, tin, the ferroalloys, gold, and silver. Most gems and some nonmetallic minerals (mica and asbestos) are found in the same associations. Uranium (pitchblende) occurs in these rocks.

Whereas these associations are well recognized, the mineral deposits themselves have a highly erratic geographical occurrence owing to the great variety of processes involving both mineral enrichment and dispersal which have occurred. The broad global pattern of rock classes with which minerals are related is delineated on the map in the illustration.

 

Employed and potential resources

 

Resources have meaning insofar as they are placed in use or are available for future exploitation. Distinction must be made between the employed and the potential resources. In practice this distinction is complex, but here only the simple geographical distinction will be noted. Employed resources are those which are significant to the present support of humans, at least locally. In general, the denser the population and the more advanced the technical arts of an area, the greater the need for production from resources, and employed resources become more nearly synonymous with all known resources. Thus, the recognized resources of the European peninsula and of the northeastern United States are mainly employed resources. On the other hand, the natural resources of the Amazon Basin, or much of Africa, Siberia are still largely potential resources.

 

Marine resources

 

Although the physical and biotic geography of the oceans is much less fully explored than that of the continents, enough is known to indicate that both living and mineral resources extend far beyond those presently exploited. The employed resources are rather sharply localized. The principal exploitation of marine animals and vegetation occurs: over the continental shelves; in the vicinity of the mixing of warm and cold currents; near large upwellings which occur particularly off the west coast of continents in lower middle latitudes; and adjacent to densely populated countries. Thus, the North Atlantic near Europe and from New England to Newfoundland contains heavily exploited fishing grounds, as do the seas near Japan, Korea, and southern California, and also waters of the Gulf of Mexico.

Minerals are derived from three separate types of marine sources: from sedimentary deposits underlying the continental shelves; from inshore deposits on the surface of the continental shelves; and from seawater. By far the most valuable of the mineral resources exploited from marine environments is petroleum; there has been an expansion of exploration, drilling, and pumping from beneath continental shelf waters, as off the Gulf coast of Louisiana, in the middle of the North Sea between Scotland and Norway, and offshore in the Persian or Arabian Gulf. Offshore placer deposits on the surface of the continental shelves yield gold, platinum, and tin. Common salt, magnesium, and bromine are derived directly from seawater.  See also: Oil and gas, offshore

Potential marine resources include the population of life-forms now exploited in some parts of the world, but not in others; animal and vegetative species now unused; fresh water from desalted seawater; and minerals so far unexploited which are in solution, are precipitated to the ocean bottom, or lie within rock below the surface of the continental shelf. One of the interesting speculative resources appears in the large quantities of so-called manganese nodules that cover some sections of sea bottoms at intermediate depths.

 

Resources of the continents

 

The resource pattern of the Earth may be summarized in a brief description of that for each continent and its neighboring waters.

 

Eurasian continent

 

As the largest landmass in the world, the Eurasian continent has the largest area of agricultural land in use, a very extensive total forest land area in which the softwood coniferous forest belt from Scandinavia to eastern Siberia predominates, and a wide variety of mineral resources. Great differences mark the major sections of the continent. The most productive agricultural areas are generally near the edge of the landmass, in western and central Europe and extending eastward into much of the central and southern sections of Russia in Europe; in the Indian subcontinent; and in mainland east Asia from the Red River valley in Vietnam northward to the Great Wall of China. The aggregate mineral endowment is outstanding and includes the largest known aggregate iron ore reserves in the world within Russia, located particularly in districts adjacent to the Urals; very substantial coal deposits, including the Ruhr field and the extensive coal beds in northern China and Manchuria; and what increasingly appears to be one of the two great concentrations of petroleum fields on Earth, namely, the Persian Gulf fields shared by a number of separate states in the Middle East. The southeastern and eastern borders of the Eurasian heartland, moreover, have some of the great, but still undeveloped, hydroelectric generation sites of the world. Off the coasts of western Europe and Japan are the two most productively employed fisheries of the world.  See also: Asia; Europe

 

Africa and Australia

 

Much of the entire area of Africa north of approximately 12°N must be classed as desert or semiarid, with few exotic water sources other than the Nile. Much of the remainder of the continent has wet-and-dry or rainforest climates, with the former predominating greatly in area. Seasonal drought, soil infertility, and widespread problems of laterization handicap agricultural exploitation. The east African highlands from Ethiopia southward, the high veld in South Africa, and the loftier sections of Zimbabwe, Rhodesia, and the Nile Valley and Delta are noteworthy exceptions. Except along the Nile there are still potential agricultural land resources, but they are comparatively minor. Associated with the extensive areas of igneous and metamorphic rocks which underlie much of the continent and particularly its southern half are outstanding deposits of metalliferous minerals, such as the copper ores astride the Zaire-Zambia boundary, the chrome-bearing ores of Zimbabwe, Rhodesia, and the gold deposits of the Witwatersrand in South Africa. Other mineral resources include diamonds, uranium, and, in Nigeria and the far north of the continent (Libya, Algeria), petroleum and natural gas. The water resources of mid-Africa include the largest potential hydroelectric power on Earth.

Similar general remarks may be made about Australia, whose much smaller area is covered mostly by desert, semiarid, and tropical wet-and-dry environments. Most of the agricultural productivity is peripheral, especially in the southeast. Metallic minerals at currently exploitable levels of size and richness support a substantial number of mining operations on the continent.  See also: Africa; Australia

 

South America

 

The land resource is dominated by the unbroken extent of rainforest and wet-and-dry climates stretching east of the Andes from Colombia to northern Argentina and by substantial areas of water-deficient territory along the west coast and in the south and northeast of the South American continent. Some highly fertile soils in flat humid subtropical lands both west and east of the Paraná–La Plata river system are of minor extent by comparison with the whole. The Amazon Basin contains the largest stand of tropical hardwood forest on Earth. Metallic mineral resources are abundant in three general regions: the Andes, the largely crystalline rock highlands of eastern and southeastern Brazil, and the low plateau south of the lower Orinoco River. The Caribbean coast of Venezuela has the most productive petroleum reserves on the continent.  See also: South America

 

North America

 

Large sections of North American lands benefit from the advantages which characterize midlatitude humid-land resources under present technology. Disadvantages of desert and semiarid environments in much of the western half of the North American continent are tempered somewhat by the interspersal of mountain ranges throughout these drier regions. Taiga and other northern climatic environments are in considerable part coincident with the igneous and metamorphic rocks of the Laurentian Shield; and tropical environments are of small extent. In sum, this continent may be considered to have one of the best-balanced sets of resources, considering its substantial endowment in minerals of many different kinds, extensive forest lands, large annually renewed fresh-water supplies, great and varied agricultural lands, and the productive fisheries off both Atlantic and Pacific coasts. In addition, evidence has accumulated that in the southern section of the continent there may exist a major concentration of petroleum and natural gas resources extending southeastward from eastern Mexico and the contiguous continental shelf beneath the waters of the Gulf of Mexico to the fringes of the western Caribbean, with eventual productivity on the order of magnitude of the cluster of fields in the Middle East. Finally, North America has the highest ratio of employed resources to land area of all continents. In addition, it still contains considerable potential resources, including vast hydroelectric potential in eastern Canada (Quebec), and extensive (mostly) untapped oil deposits in the shale oil beds of Colorado and Wyoming, and the tar sands (thick oil in sandstone) of Alberta.  See also: North America

 

 

Summary comment

 

The Earth's resource pattern has certain general characteristics. (1) Minerals usable under present technology are found in every environment, although mineral types differ according to location in sedimentary or igneous and metamorphic rock areas. Mineral exploration will continue indefinitely in all land areas, but the mineral resource possibilities of North America and the European part of the Eurasian continent have been examined in greater detail than those of any other large area. Ocean basins are the least-known part of the world as to mineral possibilities. (2) Agricultural lands and forest lands usable under present technology are dominated by those lying in midlatitudes. Sections of the taiga are important as forest resources. (3) The great potential agricultural and forest resources, if some technological improvement is assumed, lie within the humid tropical environments.

Donald J. Patton

Dale R. Lightfoot

Alifazeli=egeology.blogfa.com

 

 

Bibliography

 

 

  • M. Allaby, Earth: Our Planet and Its Resources, 1994
  • D. L. Clawson and J. S. Fisher, World Regional Geography: A Development Approach, 1998
  • G. T. Miller, Environmental Science: Sustaining the Earth, 4th ed., 1993
  • J. Rees, Natural Resources: Allocation, Economics and Policy, 1990
  • World Resources Institute, World Resources 1998–1999, 1998  
  • Alifazeli=egeology.blogfa.com