Atacama Desert

Atacama Desert

The Atacama Desert of Chile covers the northern third of the country stretching 1,000km (600 miles) and straddles the southern border of Peru. Bound on the west by barren hills and mountains on the Pacific coast it extends east into the Andes mountains. At an average elevation of about 4 kilometers (13,000 feet) it is not only the highest desert in the world but also the driest. In some parts rainfall has never been recorded. Vegetation is almost non-existent with 0.6mm to 2.1mm of rain falling around the region. Average daily temperatures range between 0°C-25°C making the Atacama relatively cool compared with the Sahara or the Great Sandy desert's.

Despite extremes and desolation there is stunning beauty. With the Andes as a backdrop the desert contains five snow topped volcanoes which are the highest volcanoes in the world and the highest elevations in South America.

Section name

Scene from Valle de la Luna (Moon Valley) near San Pedro de Atacama.

Sparsely populated and virtually rainless, the Atacama Desert forms a narrow strip of the coast of Chile.

The Atacama Desert ecoregion occupies a continuous strip for nearly 1,600 km along the narrow coast of the northern third of Chile from near Arica (18°24' S) southward to near La Serena (29°55' S) (Dillon and A. E. Hoffmann-J 1997). This desert is a sparsely populated virtually rainless plateau, running east from the Pacific Ocean to the Andes Mountains. The average width is less than 100 km. The xeric conditions extend up to1,500 masl on the drier slopes (Börgel 1973). The faulted coastal mountains (mostly 500-1000 m high) are composed of Cretaceous sediments (limestone and sandstone) over more ancient masses of crystalline rocks (Lustig 1970).

The Atacama Desert is considered to be one of the driest coastal deserts in the world. Vegetation must contend with an annual rainfall of 0.6 mm in Arica and 2.1 mm in Iquique. The Atacama becomes slightly less arid as it moves southward. The average monthly temperatures in Iquique range from 14.5 oC in September to 21 oC in March (Dillon and A. E. Hoffmann-J 1997).

Topography and substrate combine to influence the patterns of moisture availability and areas of suitable habitat. Where isolated mountains or steep coastal slopes intercept the clouds, a fog zone develops with a stratus layer concentrated against the hillsides. The moisture allows the development of fog-zone plant communities termed "lomas" (small hills) near the coast and in lower portions of numerous gorges ("quebradas") between sea level and 1,100 m. These plant formations also have been called the fertile belt, fog oases or meadows on the desert. Plant communities of the lomas consist of mixtures of annual and short-lived perennial and woody scrub vegetation.

The northern coastal zone has almost no vegetation. Among some of the few plant species found in this zone are cacti growing over 500 m- Eulychnia iquiquensis and Copiapoa sp. Near Iquique, there is large community of Tillandsia landbeckii growing at 990-1,100 m (Dillon and A. E. Hoffmann-J 1997). The valleys along streams support plant communities that are composed of trees Prosopis chilensis, P. tamarugo, Salix humboldtiana, Schinus aareira, Acacia macrantha and Caesalpinia tinctoria and other shrubby and herbaceous plants (Roig 1999). On slopes moistened by drizzle during the winter, sparse strands of Tillandsia spp. may exist in association with a few lichens.

Near the town of Antofagastsa, the region is practically devoid of vegetation except for Eulychnia iquiquensis and Copiapoa sp. Only some brush plants occur along the coastal plateaus, dependent for survival on the moisture of persistent fog, they include Heliotropium pycnophyllum, Ephedra breana and Lycium deserti (Dillon and A. E. Hoffmann-J 1997). In places away from the area of fog formation, the desert is almost lifeless. In these areas, even decomposition does not occur. Dead vegetation may be thousands of years old (Roig 1999).

The southern Atacama desert has a fog-zone vegetation with approximately 230 species of vascular plants. Euphorbia lactiflua and Eulychnia iquiquensis are dominant species in the central area of this zone. Other shrubby species in the zone include Echinopsis coquimbana, Oxalis gigantea, Lycium stenophyllum, Proustia cuneifolia, Croton chilensis, Balbisia penduncularis and Tillandsia geissei. Bromeliads are also present along the coastal flats in this southern part, and include Deuterocohni chrysantha and Puya boliviensis (Dillon and A. E. Hoffmann-J 1997).

The southernmost area in the ecoregion is near Chañaral. This area has communities of shrubs such as Skytnathus acutus, Encelia canescens, Frankenia chilensis, and Nolana rostrata. Annuals and perennials include Perityle emoryi, Oenothera coquimbensis, Ademia latistipula, Atragalus coquimbensis, Cruckshanksia verticillata, Fagonia chilensis and Tetragonia angustifolia (Dillon and A. E. Hoffmann-J 1997).

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ROD'S WORK

The Atacama Desert has one of the most unique and seemingly hostile environments on the planet. Immediate surroundings are major contributing factors influencing its formation and physical characteristics. Just to the west and immediately below is the meeting point of the oceanic Nazca Plate and the continental South American Plate. The resultant tectonic action is constantly pushing the Andes ever higher and creates powerful volcanic and seismic activity. At the eastern edge of the Nazca Plate, 100 miles (160km) off the coast, the plate is subducted leaving the Peru-Chile (Atacama) Trench. It reaches a maximum depth of 26,460 feet (8,065 m) below sea level and is approximately 3,666 miles (5,900 km) long; it covers an expanse of some 228,000 square miles (590,000 square km). The proximity to this very large body of cold water has a substantial effect. Due mainly to the westerlies; prevailing winds which drive the cool ocean Humboldt Current (or Peru) through these cold waters. Ocean air is cooled by the current without moisture being retained to generate precipitation (clouds and fog are produced however). Also upwelling occurs off Peru year-round, but off Chile only during the spring and summer. Co-incidentally cold, nutrient-rich water brought to the surface by upwelling brings about extraordinary productivity resulting in the Humboldt Current supporting the world’s largest fisheries.

Another climatic factor is that the desert lies where the westerlies and the southern trade winds intersect at 25° south. Here, the surface winds are rushing both to the north and south, so air from higher up must descend to fill the gap. Ascending air causes rain: descending air tends to prevent rain. This phenomenon is not unique to the Atacama: almost all the major deserts of the world lie between 20° and 30° north or south latitude.

The on shore result of both climatic and topographical effects is that the Atacama Desert is the driest place on Earth, and is virtually sterile because it is blocked from moisture on both sides by the Andes and the coastal mountains. The landscape and soil more closely resemble those of the planet Mars. It was thought that some soils contained no life at all until recently in an area south of Antofagasta, a new species of Deinococcus bacteria was found. Astrobiologists are studying in the Atacama to discover clues which may unlock secrets of life on other planets and the possibility of survival there. They are also studying the growth of plants in extreme places in order to develop plants that could be grown off—world or on Mars.

The lack of rain is not a new phenomenon. Dr. Tibor Dunai who spoke before the American Geophysical Union told the BBC in a news article: "We found loose sediment surfaces that would be washed away by any desert rainfall and these are older than 20 million years," he said. This is much older than other hyper-arid regions, such as the Dry Valleys of Antarctica (10-11 million years) and the Namib Desert in Africa (5 million years). "The origin of the aridity in the Atacama dates back to the opening of ocean pathways - the opening between South America and Antarctica, and between Australia and the Antarctic.

A few locations in the Atacama receive marine fog, providing sufficient moisture for hypolithic algae, lichens and even some cacti. A recent innovation has made it possible to catch water from the air. With the use of mesh nets, water is trapped and trickled off via piping into storage tanks.

Human habitation

Atacama road.

For humans to survive in and around the desert has been very challenging. It is not surprising then to discover in fact the Atacama is home to almost a million people. People are found mostly in coastal cities, fishing villages, oasis communities and scattered mining camps. In the altiplano, the descendants of the region's pre-Columbian natives (mostly Aymara and Atacama Indians) herd llamas and alpacas and grow crops with water from snowmelt streams.

Archaeological evidence indicates that the San Pedro area was the center of a Paleolithic civilization that built rock fortresses on the steep mountains encircling the valley.

The original inhabitants of the region were the Atacameños, an extinct Indian culture different from that of the Aymaras to the north and the Diaguitas to the south.

The Escondida Mine and Chuquicamata are also located within the Atacama.

The Pan-American Highway runs through the Atacama in a north-south trajectory.

The European Southern Observatory operates two major observatories in the Atacama Desert:

• The La Silla Observatory
• Located 130 km from Antofagasta at an altitude of 2635.43m and 12 km from the coast is the Paranal Observatory, which includes the Very Large Telescope.

A new radio astronomy observatory, called ALMA, is being built in the Atacama Desert by astronomers from Europe, Japan, and North America.

Another radio astronomy observatory, ACT, is being built on Cerro Toco in the Atacama Desert.

Great source of minerals

File:Chile-Tatio-Geyser.jpg

Geyser of Tatio in Atacama desert, Chile

The Atacama Desert holds major reserves of copper, gold, silver and industrial metals, it is the heart of Chile's mining industry. Chile's copper mines provide over 30% of the world's mine production of recoverable copper. It also contains the world's largest natural supply of sodium nitrate, which was mined on a large scale until the early 1940s. The Atacama border dispute between Chile and Bolivia began in the 1800s over these resources.

The Chuquicamata mine is the largest open-pit copper mine in the world, located 15 km north of the city of Calama in the region of Antofagasta. The mine is elliptical in form, with a surface of almost 8,000,000 m2, and it is 900 m deep. Copper from Chuquicamata is transported by rail southwest to Antofagasta. Approximately 30,000 people work in the remote region around the mine.

Chuquicamata is an opencast copper mine, where a relatively poor copper ore is mined in impressive huge amounts. Modern mining and smelting technology allows the usage of such depostits at unrivaled low costs. The ore contains only between 1.13% and 1.18% metals, most of it copper, but also molybdenum and selenium in a very low proportion.

Currently, the Atacama Desert is littered with approximately 170 abandoned nitrate (or "saltpeter") mining towns, almost all of which were shut down decades after the invention of synthetic nitrate in Germany at the turn of the 20th century. Some of these abandoned towns include Chacabuco, Humberstone, Santa Laura, Pedro de Valdivia, Puelma, Maria Elena and Oficina Anita. Chacabuco is a special case since it was later converted into a concentration camp during Pinochet's regime. To this day it is surrounded by 98 lost landmines and is guarded by one man who lives there alone.

The Atacama border dispute was a border dispute between Chile and Bolivia in the 1800s that ended in Chilean annexation of all of the Bolivian Coast and the southern tip of Bolivia's ally Peru, during the War of the Pacific (1879-1883). Later Peru and Argentina became involved in the dispute. Some still consider the dispute ongoing as Bolivia continues to claim a sovereign access to the Pacific Ocean.

Sources and Further Reading

• Braudel, Fernand, The perspective of the world, New York, Harper & Row, 1984, ISBN 0060153172
• Sagaris, Lake, Bone and dream : into the world's driest desert, Toronto, A.A. Knopf Canada, 2000, ISBN 0676972233
• Aarons, John and Claudio Vita-Finzi, , 1960. The useless land; a winter in the Atacama Desert, London, R. Hale, OCLC 2649656
• Roig, V. 1999. Atacama desert. Encyclopedia of deserts. University of Oklahoma Press, Norman (Oklahoma).
• Lustig, L. K. 1970. "Appraisal of research on geomorphology and surface hydrology of desert environments". Deserts of the world: An appraisal of research into their physical and biological environments. University of Arizona Press, Tucson.
• Dillon, M.O., and A.E. Hoffmann-J. 1997. "Lomas Formations of the Atacama Desert Northern Chile". Centres of Plant Diversity: A guide and Strategy for their Conservation. World Wildlife Fund. IUCN, Oxford, U.K.

External links

http://www.ls.eso.org/index.html http://www.eso.org/paranal/site/paranal.html

• Vesilind, Priit J., Parts of Chile's Atacama Desert haven't seen a drop of rain since recordkeeping began. Somehow, more than a million people squeeze life from this parched land, National Geographic, Accessed March 19, 2007
• Autonomous Robot Finds Life in Atacama Desert, Slash Dot, Accessed March 19, 2007
• Amos, Jonathan, December 8, 2005Chile desert's super-dry history, British Broadcasting Corporation, Accessed March 19, 2007
• Hudepohl, Gerhard, Atacama Desert Photographs, Atacama Photo, Accessed March 19, 2007

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