Star dunes, such as these of the Namib, indicate the winds that formed them blew from many directions (photograph by Georg Gerster).Star dunes, such as these of the Namib, indicate the winds that formed them blew from many directions (photograph by Georg Gerster).
Star dunes, such as these of the Namib, indicate the winds that formed them blew from many directions (photograph by Georg Gerster).
Radially symmetrical,star dunesare pyramidal sand mounds with slipfaces on three or more arms that radiate from the high center of the mound. They tend to accumulate in areas with multidirectional wind regimes. Star dunes grow upward rather than laterally. They dominate the Grand Erg Oriental of the Sahara. In other deserts, they occur around the margins of the sand seas, particularly near topographic barriers. In the southeast Badain Jaran Desert of China, the star dunes are up to 500 meters tall and may be the tallest dunes on Earth.
Linear dunes advance on small playas east of Lake Eyre in the Simpson Desert of central Australia (photograph by C. Twidale).Linear dunes advance on small playas east of Lake Eyre in the Simpson Desert of central Australia (photograph by C. Twidale).
Linear dunes advance on small playas east of Lake Eyre in the Simpson Desert of central Australia (photograph by C. Twidale).
Linear dunes in the Western Desert of Egypt (photograph by Carol Breed).Linear dunes in the Western Desert of Egypt (photograph by Carol Breed).
Linear dunes in the Western Desert of Egypt (photograph by Carol Breed).
Oval or circular mounds that generally lack a slipface,dome dunesare rare and occur at the far upwind margins of sand seas.
U-shaped mounds of sand with convex noses trailed by elongated arms areparabolic dunes. Sometimes these dunes are called U-shaped, blowout, or hairpin dunes, and they are well known in coastal deserts. Unlike crescentic dunes, their crests point upwind. The elongated arms of parabolic dunes follow rather than lead because they have been fixed by vegetation, while the bulk of the sand in the dune migrates forward. The longest known parabolic dune has a trailing arm 12 kilometers long.
Small crescentic dunes occur on the crests of these complex dome dunes of Saudi Arabia’s Empty Quarter (photograph by Elwood Friesen).Small crescentic dunes occur on the crests of these complex dome dunes of Saudi Arabia’s Empty Quarter (photograph by Elwood Friesen).
Small crescentic dunes occur on the crests of these complex dome dunes of Saudi Arabia’s Empty Quarter (photograph by Elwood Friesen).
Ripples and horns of this crescentic dune in Egypt indicate that the dune is moving right to left (photograph by John Olsen).Ripples and horns of this crescentic dune in Egypt indicate that the dune is moving right to left (photograph by John Olsen).
Ripples and horns of this crescentic dune in Egypt indicate that the dune is moving right to left (photograph by John Olsen).
Occurring wherever winds periodically reverse direction,reversing dunesare varieties of any of the above types. These dunes typically have major and minor slipfaces oriented in opposite directions.
All these dune types may occur in three forms:simple,compound, andcomplex. Simple dunes are basic forms with a minimum number of slipfaces that define the geometric type. Compound dunes are large dunes on which smaller dunes of similar type and slipface orientation are superimposed, and complex dunes are combinations of two or more dune types. A crescentic dune with a star dune superimposed on its crest is the most common complex dune. Simple dunes represent a wind regime that has not changed in intensity or direction since the formation of the dune, while compound and complex dunes suggest that the intensity and direction of the wind has changed.
The northern Mojave Desert. The Landsat Thematic Mapper (TM) acquires data in seven bands of the electromagnetic spectrum. On this image, white and yellow colors indicate rocks rich in clay minerals and limonite in rocks of red and yellow hues. The large concentrations of limonite and clays may indicate mineral deposits exposed at the surface or buried up to several thousand feet below it (photograph courtesy of Melvin Podwysocki).The northern Mojave Desert. The Landsat Thematic Mapper (TM) acquires data in seven bands of the electromagnetic spectrum. On this image, white and yellow colors indicate rocks rich in clay minerals and limonite in rocks of red and yellow hues. The large concentrations of limonite and clays may indicate mineral deposits exposed at the surface or buried up to several thousand feet below it (photograph courtesy of Melvin Podwysocki).
The northern Mojave Desert. The Landsat Thematic Mapper (TM) acquires data in seven bands of the electromagnetic spectrum. On this image, white and yellow colors indicate rocks rich in clay minerals and limonite in rocks of red and yellow hues. The large concentrations of limonite and clays may indicate mineral deposits exposed at the surface or buried up to several thousand feet below it (photograph courtesy of Melvin Podwysocki).
The world’s deserts are generally remote, inaccessible, and inhospitable. Hidden among them, however, are hydrocarbon reservoirs, evaporites, and other mineral deposits, as well as human artifacts preserved for centuries by the arid climate. In these harsh environments, the information and perspective required to increase our understanding of arid-land geology and resources often depends on remote-sensing methods. Remote sensing is the collection of information about an object without being in direct physical contact with it.
Remote-sensing instruments in Earth-orbit satellites measure radar, visible light, and infrared radiation. Radar imaging systems provide their own source of electromagnetic energy, so they can operate at any time of day or night. Additionally, clouds and all but the most severe storms are transparent to radar.
The first Shuttle Imaging Radar System (SIR-A), flown on the U.S. space shuttleColumbiain 1981, recorded images that show buried fluvial topography, faults, and intrusive bodies otherwise concealed beneath sand sheets and dunes of the Western Desert in Egypt and the Sudan. Most of these features are not visible from the ground. The radar signal penetrated loose dry sands and returned images of buried river channels not visible at the surface. These images helped find new archeologic sites and sources of potable water in the desert. These “radar rivers” are the remnants of a now vanished major river system that flowed across Africa some 20 million years before the development of the Nile River system. Radar imagery also is a powerful tool for exploring for placer mineral deposits in arid lands.
In 1972, the United States launched the first of a group of unmanned satellites collectively known as Landsat. Landsat satellites carry sensors that record “light,” or portions of the electromagnetic spectrum, as it reflects off the Earth. Landsat acquires digital data that are converted into an image.
The Landsat simulated true color mosaic (left) shows the Selima Sand Sheet covering all but rocky areas of the Sahara Desert in Sudan. On the right, a 50-kilometer-wide strip of Shuttle Imaging Radar, SIR-A, is placed over the Landsat mosaic to reveal old stream channels and geologic structures like these. Structures that are otherwise invisible under the surface sands are potential sources of water, placer minerals, ancient artifacts, and information on changes of climate in arid areas (courtesy of USGS Image Processing Facility, Flagstaff).The Landsat simulated true color mosaic (left) shows the Selima Sand Sheet covering all but rocky areas of the Sahara Desert in Sudan. On the right, a 50-kilometer-wide strip of Shuttle Imaging Radar, SIR-A, is placed over the Landsat mosaic to reveal old stream channels and geologic structures like these. Structures that are otherwise invisible under the surface sands are potential sources of water, placer minerals, ancient artifacts, and information on changes of climate in arid areas (courtesy of USGS Image Processing Facility, Flagstaff).
The Landsat simulated true color mosaic (left) shows the Selima Sand Sheet covering all but rocky areas of the Sahara Desert in Sudan. On the right, a 50-kilometer-wide strip of Shuttle Imaging Radar, SIR-A, is placed over the Landsat mosaic to reveal old stream channels and geologic structures like these. Structures that are otherwise invisible under the surface sands are potential sources of water, placer minerals, ancient artifacts, and information on changes of climate in arid areas (courtesy of USGS Image Processing Facility, Flagstaff).
The scarcity of vegetation makes spectral remote sensing especially effective in arid lands. Rocks containing limonite, a hydrous iron oxide, may be identified readily from Landsat Multispectral Scanner data. The Landsat Thematic Mapper (TM) has increased our ability to detect and map the distribution of minerals in volcanic rocks and related mineral deposits in arid and semiarid lands.
More than a million images of Earth have been acquired by the Landsat satellites. A Landsat image may be viewed as a single band in black-and-white, or as a combination represented by three colors, called a color composite. The most widely used Landsat color image is called a false-color composite because it reproduces the infrared band (invisible to the naked eye) as red, the red band as green, and the green band as blue. Healthy vegetation in a false-color composite is red.
Desert studies still are hampered in many regions by lack of accurate climate data. Most desert weather stations are in oases surrounded by trees and buildings and have been subjected to many location and elevation changes throughout the life of the station. Data from oases do not reflect conditions from the surrounding desert. A wide variety of instruments has been used to record measurements over varying lengths of time and in different formats, making data difficult to interpret and compare.
To overcome some of these problems in deserts of the American Southwest, the U.S. Geological Survey (USGS) established its Desert Winds Project to measure in a standard format several key meteorologic characteristics of arid lands. Project scientists have successfully established instrument stations to measure wind-speed, including peak gusts, which alter the landforms the most. A station recorded a windstorm near Vicksburg, Arizona, for example, with peak gusts of almost 150 kilometers per hour. Using low-maintenance, automatic, solar-powered sensors, the stations also measure wind direction, precipitation, humidity, soil and air temperatures, and barometric pressure at specific heights above the surface. Data are sampled at 6-minute intervals and transmitted every 30 minutes to a Geostationary Operational Environmental Satellite (GOES). From GOES, the data are transmitted to the USGS laboratory in Flagstaff, Arizona.
The Desert Winds Project’s investigators combine analyses of data with detailed geologic field studies and repetitive remote-sensing coverage in order to investigate and understand the long-term changes produced by wind in deserts of differing geologic and climatic types.
This geometeorologic station of the Desert Winds Project measures wind speed and direction, soil and air temperature, and precipitation and humidity in the Great Basin Desert (photograph by Carol Breed).This geometeorologic station of the Desert Winds Project measures wind speed and direction, soil and air temperature, and precipitation and humidity in the Great Basin Desert (photograph by Carol Breed).
This geometeorologic station of the Desert Winds Project measures wind speed and direction, soil and air temperature, and precipitation and humidity in the Great Basin Desert (photograph by Carol Breed).
Nitrate workings in a broad valley in the Atacama Desert of northern Chile, where saline-cemented surficial deposits formed near a playa lake (photograph by George Ericksen).Nitrate workings in a broad valley in the Atacama Desert of northern Chile, where saline-cemented surficial deposits formed near a playa lake (photograph by George Ericksen).
Nitrate workings in a broad valley in the Atacama Desert of northern Chile, where saline-cemented surficial deposits formed near a playa lake (photograph by George Ericksen).
Some mineral deposits are formed, improved, or preserved by geologic processes that occur in arid lands as a consequence of climate. Ground water leaches ore minerals and redeposits them in zones near the water table. This leaching process concentrates these minerals as ore that can be mined. Of the 15 major types of mineral deposits in the Western Hemisphere formed by action of ground water, 13 occur in deserts.
Evaporation in arid lands enriches mineral accumulation in their lakes. Playas may be sources of mineral deposits formed by evaporation. Water evaporating in closed basins precipitates minerals such as gypsum, salts (including sodium nitrate and sodium chloride), and borates. The minerals formed in these evaporite deposits depend on the composition and temperature of the saline waters at the time of deposition.
Significant evaporite resources occur in the Great Basin Desert of the United States, mineral deposits made forever famous by the “20-mule teams” that once hauled borax-laden wagons from Death Valley to the railroad. Boron, from borax and borate evaporites, is an essential ingredient in the manufacture of glass, ceramics, enamel, agricultural chemicals, water softeners, and pharmaceuticals. Borates are mined from evaporite deposits at Searles Lake, California, and other desert locations. The total value of chemicals that have been produced from Searles Lake substantially exceeds $1 billion.
The Atacama Desert of South America is unique among the deserts of the world in its great abundance of saline minerals. Sodium nitrate has been mined for explosives and fertilizer in the Atacama since the middle of the 19th century. Nearly 3 million metric tons were mined during World War I.
Valuable minerals located in arid lands include copper in the United States, Chile, Peru, and Iran; iron and lead-zinc ore in Australia; chromite in Turkey; and gold, silver, and uranium depositsin Australia and the United States. Nonmetallic mineral resources and rocks such as beryllium, mica, lithium, clays, pumice, and scoria also occur in arid regions. Sodium carbonate, sulfate, borate, nitrate, lithium, bromine, iodine, calcium, and strontium compounds come from sediments and nearsurface brines formed by evaporation of inland bodies of water, often during geologically recent times.
This open-pit mine in the Sonoran Desert near Ajo, Arizona, has exposed an elliptical copper deposit about 1,000 meters long and 750 meters wide. The copper ore mined here is in a bed that averages 150 meters in thickness (photograph by Peter Kresan).This open-pit mine in the Sonoran Desert near Ajo, Arizona, has exposed an elliptical copper deposit about 1,000 meters long and 750 meters wide. The copper ore mined here is in a bed that averages 150 meters in thickness (photograph by Peter Kresan).
This open-pit mine in the Sonoran Desert near Ajo, Arizona, has exposed an elliptical copper deposit about 1,000 meters long and 750 meters wide. The copper ore mined here is in a bed that averages 150 meters in thickness (photograph by Peter Kresan).
The Green River Formation of Colorado, Wyoming, and Utah contains alluvial fan deposits and playa evaporites created in a huge lake whoselevel fluctuated for millions of years. Economically significant deposits of trona, a major source of sodium compounds, and thick layers of oil shale were created in the arid environment.
Trona mine at Searles Lake, California (photograph by John Keith).Trona mine at Searles Lake, California (photograph by John Keith).
Trona mine at Searles Lake, California (photograph by John Keith).
Some of the more productive petroleum areas on Earth are found in arid and semiarid regions of Africa and the Mideast, although the oil reservoirs were originally formed in shallow marine environments. Recent climate change has placed these reservoirs in an arid environment.
Other oil reservoirs, however, are presumed to be eolian in origin and are presently found in humid environments. The Rotliegendes, a hydrocarbon reservoir in the North Sea, is associated with extensive evaporite deposits. Many of the major U.S. hydrocarbon resources may come from eolian sands. Ancient alluvial fan sequences may also be hydrocarbon reservoirs.
The Sahelian drought that began in 1968 was responsible for the deaths of between 100,000 and 250,000 people, the disruption of millions of lives, and the collapse of the agricultural bases of five countries (photograph by Daniel Stiles, UNEP).The Sahelian drought that began in 1968 was responsible for the deaths of between 100,000 and 250,000 people, the disruption of millions of lives, and the collapse of the agricultural bases of five countries (photograph by Daniel Stiles, UNEP).
The Sahelian drought that began in 1968 was responsible for the deaths of between 100,000 and 250,000 people, the disruption of millions of lives, and the collapse of the agricultural bases of five countries (photograph by Daniel Stiles, UNEP).
The world’s great deserts were formed by natural processes interacting over long intervals of time. During most of these times, deserts have grown and shrunk independent of human activities. Paleodeserts, large sand seas now inactive because they are stabilized by vegetation, extend well beyond the present margins of core deserts, such as the Sahara. In some regions, deserts are separated sharply from surrounding, less arid areas by mountains and other contrasting landforms that reflect basic structural differences in the regional geology. In other areas, desert fringes form a gradual transition from a dry to a more humid environment, making it more difficult to define the desert border.
Overgrazing has made the Rio Puerco Basin of central New Mexico one of the most eroded river basins of the American West and has increased the high sediment content of the river (photograph by Terrence Moore).Overgrazing has made the Rio Puerco Basin of central New Mexico one of the most eroded river basins of the American West and has increased the high sediment content of the river (photograph by Terrence Moore).
Overgrazing has made the Rio Puerco Basin of central New Mexico one of the most eroded river basins of the American West and has increased the high sediment content of the river (photograph by Terrence Moore).
Linear dunes of the Sahara Desert encroach on Nouakchott, the capital of Mauritania. The dunes border a mosque at left (photograph by Georg Gerster).Linear dunes of the Sahara Desert encroach on Nouakchott, the capital of Mauritania. The dunes border a mosque at left (photograph by Georg Gerster).
Linear dunes of the Sahara Desert encroach on Nouakchott, the capital of Mauritania. The dunes border a mosque at left (photograph by Georg Gerster).
These transition zones have very fragile, delicately balanced ecosystems. Desert fringes often are a mosaic of microclimates. Small hollows support vegetation that picks up heat from the hot winds and protects the land from the prevailing winds. After rainfall the vegetated areas are distinctly cooler than the surroundings. In these marginal areas, human activity may stress the ecosystem beyond its tolerance limit, resulting in degradation of the land. By pounding the soil with their hooves, livestock compact the substrate, increase the proportion of fine material, and reduce the percolation rate of the soil, thus encouraging erosion by wind and water. Grazing and the collection of firewood reduces or eliminates plants that help to bind the soil.
This degradation of formerly productive land—desertification—is a complex process. It involves multiple causes, and it proceeds at varying rates in different climates. Desertification may intensify a general climatic trend toward greater aridity, or it may initiate a change in local climate.
Desertification does not occur in linear, easily mappable patterns. Deserts advance erratically, forming patches on their borders. Areas far from natural deserts can degrade quickly to barren soil, rock, or sand through poor land management. The presence of a nearby desert has no direct relationship to desertification. Unfortunately, an area undergoing desertification is brought to public attention only after the process is well underway. Often little or no data are available to indicate the previous state of the ecosystem or the rate of degradation. Scientists still question whether desertification, as a process of global change, is permanent or how and when it can be halted or reversed.
Camels and other animals trample the soil in the semiarid Sahel of Africa as they move to water holes such as this one in Chad (photograph courtesy of the U.S. Agency for International Development).Camels and other animals trample the soil in the semiarid Sahel of Africa as they move to water holes such as this one in Chad (photograph courtesy of the U.S. Agency for International Development).
Camels and other animals trample the soil in the semiarid Sahel of Africa as they move to water holes such as this one in Chad (photograph courtesy of the U.S. Agency for International Development).
Desertification became well known in the 1930’s, when parts of the Great Plains in the United States turned into the “Dust Bowl” as a result of drought and poor practices in farming, although the term itself was not used until almost 1950. During the dust bowl period, millions of people were forced to abandon their farms and livelihoods. Greatly improved methods of agriculture and land and water management in the Great Plains have prevented that disaster from recurring, but desertification presently affects millions of people in almost every continent.
Off-road vehicles significantly increase soil loss in the delicate desert environment of the western United States. In a few seconds, soils that took hundreds of years to develop can be destroyed (photograph by Terrence Moore).Off-road vehicles significantly increase soil loss in the delicate desert environment of the western United States. In a few seconds, soils that took hundreds of years to develop can be destroyed (photograph by Terrence Moore).
Off-road vehicles significantly increase soil loss in the delicate desert environment of the western United States. In a few seconds, soils that took hundreds of years to develop can be destroyed (photograph by Terrence Moore).
Increased population and livestock pressure on marginal lands has accelerated desertification. In some areas, nomads moving to less arid areas disrupt the local ecosystem and increase the rate of erosion of the land. Nomads are trying to escape the desert, but because of their land-use practices, they are bringing the desert with them.
It is a misconception that droughts cause desertification. Droughts are common in arid and semiarid lands. Well-managed lands can recover from drought when the rains return. Continued land abuse during droughts, however, increases land degradation. By 1973, the drought that began in 1968 in the Sahel of West Africa and the land-use practices there had caused the deaths of more than 100,000 people and 12 million cattle, as well as the disruption of social organizations from villages to the national level.
While desertification has received tremendous publicity by the political and news media, there are still many things that we don’t know about the degradation of productive lands and the expansion of deserts. In 1988 Ridley Nelson pointed out in an important scientific paper thatthe desertification problem and processes are not clearly defined. There is no consensus among researchers as to the specific causes, extent, or degree of desertification. Contrary to many popular reports, desertification is actually a subtle and complex process of deterioration that may often be reversible.
Goat seeks food in the sparsely vegetated Sahel of Africa (photograph courtesy of the U.S. Agency for International Development).Goat seeks food in the sparsely vegetated Sahel of Africa (photograph courtesy of the U.S. Agency for International Development).
Goat seeks food in the sparsely vegetated Sahel of Africa (photograph courtesy of the U.S. Agency for International Development).
In the last 25 years, satellites have begun to provide the global monitoring necessary for improving our understanding of desertification. Landsat images of the same area, taken several years apart but during the same point in the growing season, may indicate changes in the susceptibility of land to desertification. Studies using Landsat data help demonstrate the impact of people and animals on the Earth. However, other types of remote-sensing systems, land-monitoring networks, and global data bases of field observations are needed before the process and problems of desertification will be completely understood.
At the local level, individuals and governments can help to reclaim and protect their lands. In areas of sand dunes, covering the dunes with large boulders or petroleum will interrupt the wind regime near the face of the dunes and prevent the sand from moving. Sand fences are used throughout the Middle East and the United States, in the same way snow fences are used in the north. Placement of straw grids, each up to a square meter in area, will also decrease the surface wind velocity. Shrubs and trees planted within the grids are protected by the straw untilthey take root. In areas where some water is available for irrigation, shrubs planted on the lower one-third of a dune’s windward side will stabilize the dune. This vegetation decreases the wind velocity near the base of the dune and prevents much of the sand from moving. Higher velocity winds at the top of the dune level it off and trees can be planted atop these flattened surfaces.
Straw grids (one of which is shown above) and vegetation irrigated by water from the Yellow River stabilize dunes in this part of China’s Tengger Desert (shown below) and protect a nearby railroad from windblown sand.Straw grids (one of which is shown above) and vegetation irrigated by water from the Yellow River stabilize dunes in this part of China’s Tengger Desert (shown below) and protect a nearby railroad from windblown sand.
Straw grids (one of which is shown above) and vegetation irrigated by water from the Yellow River stabilize dunes in this part of China’s Tengger Desert (shown below) and protect a nearby railroad from windblown sand.
Tengger DesertTengger Desert
Tengger Desert
Oases and farmlands in windy regions can be protected by planting tree fences or grass belts. Sand that manages to pass through the grass belts can be caught in strips of trees planted as wind breaks 50 to 100 meters apart adjacent to the belts. Small plots of trees may also be scattered inside oases to stabilize the area. On a much larger scale, a “Green Wall,” which will eventually stretch more than 5,700 kilometers in length, much longer than the famous Great Wall, is being planted in northeastern China to protect “sandy lands”—deserts believed to have been created by human activity.
More efficient use of existing water resources and control of salinization are other effective tools for improving arid lands. New ways are being sought to use surface-water resources such as rain water harvesting or irrigating with seasonal runoff from adjacent highlands. New ways are also being sought to find and tap groundwater resources and to develop more effective ways of irrigating arid and semiarid lands. Research on the reclamation of deserts also is focusing on discovering proper crop rotation to protect the fragile soil, on understanding how sand-fixing plants can be adapted to local environments, and on how grazing lands and water resources can be developed effectively without being overused.
From wasteland to vineyard. Ground water and underground channels help this vineyard flourish on land reclaimed from desert pavement in China’s Turpan Depression.From wasteland to vineyard. Ground water and underground channels help this vineyard flourish on land reclaimed from desert pavement in China’s Turpan Depression.
From wasteland to vineyard. Ground water and underground channels help this vineyard flourish on land reclaimed from desert pavement in China’s Turpan Depression.
If we are to stop and reverse the degradation of arid and semiarid lands, we must understand how and why the rates of climate change, population growth, and food production adversely affect these environments. The most effective intervention can come only from the wise use of the best earth-science information available.
Bagnold, R. A., 1941, The physics of blown sand and desert dunes: Methuen, London, 265 p. (A classic treatise concerning the origin and evolution of dunes.)Breed, C. S., and others, 1979, Regional studies of sand seas, using Landsat (ERTS) imagery:inMcKee, E. D., ed., A study of global sand seas: U.S. Geological Survey Professional Paper 1052, p. 305-397. (A study of selected sand seas based on analysis of remote sensing images, surface wind summaries, and available literature.)Cook, R. U., and Warren, Andrew, 1973, Geomorphology in deserts: University of California Press, Berkeley, California, 374 p. (Examines the nature of landforms, soils, and geomorphological processes in the world’s deserts.)Eigeland, Tor, and others, 1982, The desert realm: National Geographic Society, Washington, 304 p. (A well illustrated discussion of deserts of America, Africa, Asia, and Australia.)Ericksen, G. E., 1983, The Chilean nitrate deposits: American Scientist, v. 71, p. 366-374. (A discussion of the origin of the Chilean nitrate deposits which has puzzled scientists for more than 100 years.)Gerster, Georg, 1960, Sahara-desert of destiny: Coward-McCann, New York, 302 p. (How plants, animals, and people survive in the Sahara.)Greeley, Ronald, and Iversen, J. D., 1985, Wind as a geological process on Earth, Mars, Venus and Titan: Cambridge University Press, New York, 333 p. (Expands the classic work of Bagnold to discuss eolian processes in a planetary context. Describes the processes on all moons and terrestrial planets with atmospheres.)Hare, F. K., 1983, Climate on the desert fringe:inGardner, Ritz, and Scoging, Helen, eds., Mega-geomorphology: Clarendon Press, Oxford, p. 134-151. (The margins of many deserts are affected by tension between society and environment. This paper summarizes the climatology of arid zones.)MacMahon, James A., 1985, Deserts: Alfred A. Knopf, Inc., New York, 640 p. (An Audubon Society Nature Guide to the deserts of the United States, and their inhabitants.)McCauley, J. F., and others, 1984, Remote monitoring of processes that shape desert surfaces: The Desert Winds Project: U.S. Geological Survey Bulletin 1634, 19 p. (Describes a new study on collecting weather data from solar-powered data-collection platforms in deserts. The data are relayed by a GOES satellite to the USGS in Flagstaff, Arizona, and converted to graphic form.)Meigs, Peveril, 1953, World distribution of arid and semi-arid homoclimates:inReviews of research on arid zone hydrology: Paris, United Nations Educational, Scientific, and Cultural Organization, Arid Zone Programme-1, p. 203-209. (Classifies arid lands according to precipitation.)Nelson, R., 1988, Dryland management: the desertification problem: Environmental Department Working Paper No. 8, Washington: World Bank, 42 p. (An excellent review of the present state of knowledge concerning desertification.)Tolba, M. K., 1984, Desertification is stoppable: Arid Lands Newsletter No. 21, p. 2-9. (A discussion of the problems involved in preventing desertification and reclaiming arid lands.)Walker, A.S., 1986, Eolian geomorphology:inShort, N.M., and Blair, R.W., eds., Geomorphology from space: a global overview of regional landforms: NASA SP-486, p. 447-520 (a brief review of desert processes).Warren, A. and Agnew, C., 1988, An assessment of desertification and land degradation in arid and semi-arid areas: International Institute for Environment and Development, Drylands Programme, Paper 2, London: IIED, 103 p. (An evaluation of land degradation problems.)
Bagnold, R. A., 1941, The physics of blown sand and desert dunes: Methuen, London, 265 p. (A classic treatise concerning the origin and evolution of dunes.)
Breed, C. S., and others, 1979, Regional studies of sand seas, using Landsat (ERTS) imagery:inMcKee, E. D., ed., A study of global sand seas: U.S. Geological Survey Professional Paper 1052, p. 305-397. (A study of selected sand seas based on analysis of remote sensing images, surface wind summaries, and available literature.)
Cook, R. U., and Warren, Andrew, 1973, Geomorphology in deserts: University of California Press, Berkeley, California, 374 p. (Examines the nature of landforms, soils, and geomorphological processes in the world’s deserts.)
Eigeland, Tor, and others, 1982, The desert realm: National Geographic Society, Washington, 304 p. (A well illustrated discussion of deserts of America, Africa, Asia, and Australia.)
Ericksen, G. E., 1983, The Chilean nitrate deposits: American Scientist, v. 71, p. 366-374. (A discussion of the origin of the Chilean nitrate deposits which has puzzled scientists for more than 100 years.)
Gerster, Georg, 1960, Sahara-desert of destiny: Coward-McCann, New York, 302 p. (How plants, animals, and people survive in the Sahara.)
Greeley, Ronald, and Iversen, J. D., 1985, Wind as a geological process on Earth, Mars, Venus and Titan: Cambridge University Press, New York, 333 p. (Expands the classic work of Bagnold to discuss eolian processes in a planetary context. Describes the processes on all moons and terrestrial planets with atmospheres.)
Hare, F. K., 1983, Climate on the desert fringe:inGardner, Ritz, and Scoging, Helen, eds., Mega-geomorphology: Clarendon Press, Oxford, p. 134-151. (The margins of many deserts are affected by tension between society and environment. This paper summarizes the climatology of arid zones.)
MacMahon, James A., 1985, Deserts: Alfred A. Knopf, Inc., New York, 640 p. (An Audubon Society Nature Guide to the deserts of the United States, and their inhabitants.)
McCauley, J. F., and others, 1984, Remote monitoring of processes that shape desert surfaces: The Desert Winds Project: U.S. Geological Survey Bulletin 1634, 19 p. (Describes a new study on collecting weather data from solar-powered data-collection platforms in deserts. The data are relayed by a GOES satellite to the USGS in Flagstaff, Arizona, and converted to graphic form.)
Meigs, Peveril, 1953, World distribution of arid and semi-arid homoclimates:inReviews of research on arid zone hydrology: Paris, United Nations Educational, Scientific, and Cultural Organization, Arid Zone Programme-1, p. 203-209. (Classifies arid lands according to precipitation.)
Nelson, R., 1988, Dryland management: the desertification problem: Environmental Department Working Paper No. 8, Washington: World Bank, 42 p. (An excellent review of the present state of knowledge concerning desertification.)
Tolba, M. K., 1984, Desertification is stoppable: Arid Lands Newsletter No. 21, p. 2-9. (A discussion of the problems involved in preventing desertification and reclaiming arid lands.)
Walker, A.S., 1986, Eolian geomorphology:inShort, N.M., and Blair, R.W., eds., Geomorphology from space: a global overview of regional landforms: NASA SP-486, p. 447-520 (a brief review of desert processes).
Warren, A. and Agnew, C., 1988, An assessment of desertification and land degradation in arid and semi-arid areas: International Institute for Environment and Development, Drylands Programme, Paper 2, London: IIED, 103 p. (An evaluation of land degradation problems.)
The metric units used in this publication can be converted to English units by using the approximate conversions given below:Length1 kilometer0.6 of a mile1 meter39.37 inches1 centimeter0.4 inch1 millimeter0.04 inchArea1 sq. kilometer0.04 sq. mile1 sq. meter1.2 sq. yards1 sq. centimeter0.155 sq. inchTemperatureTo convert °Celsius to °Fahrenheit, multiply °C by 1.8 and add 32.To convert °Fahrenheit to °Celsius, subtract 32 from °F and divide the result by 1.8.
The metric units used in this publication can be converted to English units by using the approximate conversions given below:
Landsat image shows complex linear and crescentic dunes in the northeastern Taklimakan Desert of China.Landsat image shows complex linear and crescentic dunes in the northeastern Taklimakan Desert of China.
Landsat image shows complex linear and crescentic dunes in the northeastern Taklimakan Desert of China.
In this desert there are a great many evil spirits and also hot winds; those who encounter them perish to a man. There are neither birds above nor beasts below. Gazing on all sides as far as the eye can reach in order to mark the track, no guidance is to be obtained save from the rotting bones of dead men, which point the way.
Explorer Fa Xian describing the Taklimakan Desert of China about 400 A.D.
This publication is one of a series of general interest publications prepared by the U.S. Geological Survey to provide information about the earth sciences, natural resources, and the environment. To obtain a catalog of additional titles in the series “General Interest Publications of the U.S. Geological Survey,” write:U.S. Geological SurveyBranch of DistributionP.O. Box 25286Denver, CO 80225★ U. S. GOVERNMENT PRINTING OFFICE : 1992 0-332-326 QL 2
This publication is one of a series of general interest publications prepared by the U.S. Geological Survey to provide information about the earth sciences, natural resources, and the environment. To obtain a catalog of additional titles in the series “General Interest Publications of the U.S. Geological Survey,” write:
U.S. Geological SurveyBranch of DistributionP.O. Box 25286Denver, CO 80225
U.S. Geological Survey
Branch of Distribution
P.O. Box 25286
Denver, CO 80225
★ U. S. GOVERNMENT PRINTING OFFICE : 1992 0-332-326 QL 2
As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally-owned public lands and natural and cultural resources. This includes fostering wise use of our land and water resources, protecting our fish and wildlife, preserving the environmental and cultural values of our national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also promotes the goals of the Take Pride in America campaign by encouraging stewardship and citizen responsibility for the public land and promoting citizen participation in their care. The Department also has a major responsibility for American Indian reservation communities and for people who live in Island Territories under U.S. Administration.
Granite Mountain in the Great Basin Desert (photograph by Terrence Moore).Granite Mountain in the Great Basin Desert (photograph by Terrence Moore).
Granite Mountain in the Great Basin Desert (photograph by Terrence Moore).
Sonoran Desert (photograph by Peter Kresan).Sonoran Desert (photograph by Peter Kresan).
Sonoran Desert (photograph by Peter Kresan).
Zabriskie Point in Death Valley, California (photograph by Peter Kresan).Zabriskie Point in Death Valley, California (photograph by Peter Kresan).
Zabriskie Point in Death Valley, California (photograph by Peter Kresan).
Artists Point in Monument Valley (photograph by Peter Kresan).Artists Point in Monument Valley (photograph by Peter Kresan).
Artists Point in Monument Valley (photograph by Peter Kresan).
Death Valley, California (photograph by Cecil Stoughton).Death Valley, California (photograph by Cecil Stoughton).
Death Valley, California (photograph by Cecil Stoughton).
Cacti in the Sonoran Desert (photograph by John Olson).Cacti in the Sonoran Desert (photograph by John Olson).
Cacti in the Sonoran Desert (photograph by John Olson).
Back Cover