El Tatio
El Tatio is a geothermal field with many geysers located in the Andes Mountains of northern Chile at above mean sea level. It is the third-largest geyser field in the world and the largest in the Southern Hemisphere. Various meanings have been proposed for the name "El Tatio", including "oven" or "grandfather". The geothermal field has many geysers, hot springs, and associated sinter deposits. The water from these hot springs eventually forms the Rio Salado, a major tributary of the Rio Loa, significantly increasing the amount of arsenic in the river. The geothermal vents are sites of populations of extremophile microorganisms such as hyperthermophiles, and El Tatio has been studied as an analogue for the early Earth and possible past life on Mars.
El Tatio lies at the western foot of a series of stratovolcanoes which runs along the border between Chile and Bolivia. This series of volcanoes is part of the Central Volcanic Zone, and of the Altiplano–Puna volcanic complex - a system of large calderas and associated ignimbrites which were the sources of supereruptions between 10 million and 1 million years ago. Some of these calderas may be the source of heat for the El Tatio geothermal system. There are no recorded eruptions of the Tatio volcanoes in the historical period.
The field is a major tourism destination in northern Chile. It was prospected over the last century for geothermal power production, but development efforts were discontinued after a major incident in 2009 in which a geothermal well blew out, creating a steam column. The blowout caused a political controversy about geothermal power development in Chile.
Name and research history
The term "tatio" comes from the nearly-extinct Kunza language; known meanings of the word include 'to appear' and 'oven', but it has also been translated as 'grandfather' or 'burnt'. The geyser field is also known as the Copacoya geysers; Copacoya is the name of a mountain in the area.The earliest mentions of geysers in the region are from the late 19th century, and they were already well known by 1952. The first geothermal prospecting of the field occurred in the 1920s and the field was mentioned in academic literature in 1943. More systematic research took place in 1967–1982; most research on this geothermal field was done in the context of geothermal prospecting.
Geography and geomorphology
El Tatio is part of the Central Volcanic Zone, a segment of the Andes between 14° and 28° southern latitude where the Andes are volcanically active. This volcanism manifests itself with about 10 silicic caldera complexes of the Altiplano–Puna volcanic complex and more than 50 recently active volcanoes; Lascar volcano erupted in 1993 and produced a tall eruption column.
East of the field, andesitic stratovolcanoes reach elevations of about. From north to south, the andesitic stratovolcanoes include the or high Cerro Deslinde which is the highest in the area, the high Cerro El Volcan, the high Cordillera del Tatio and the high Volcan Tatio, which collectively form the El Tatio volcanic group which is part of a larger north-south trending chain of Pleistocene volcanoes. The Sierra de Tucle lies to the southwest of the field.
Mountains southwest of El Tatio include the high Alto Ojo del Cablor range, while high Cerro Copacoya is situated northwest of the geothermal field. Volcanism with dacitic composition, older than the easterly stratovolcanoes, has occurred west of El Tatio; this volcanism was known as the "liparitic formation" and it covers large areas in the region.
Firn and snow fields were reported in the middle 20th century on the El Tatio volcanic group, at elevations of. The region is too dry to support glaciers today, but in the past higher moisture allowed their formation on mountains of this part of the Andes. Glacially eroded mountains and moraines testify to their existence in the form of large valley glaciers. A large moraine complex, including both terminal structures and well-developed lateral moraines, can be found north of the geyser field and reflects the past existence of a long glacier, the longest valley glacier in the region. Two more moraine systems extend westward both northeast and southeast of El Tatio, and the terrain surrounding the geyser field is covered by sands that are interpreted as glacial outwash sands. Surface exposure dating indicates that some moraines were emplaced at or before the Last Glacial Maximum and others in a time period 35,000 to 40,000 years before present. Smaller moraines at higher altitude may date to the Antarctic Cold Reversal or the Younger Dryas climate periods; moraines related to the Lake Tauca stage are either absent or restricted to high elevation sites.
Drainage in the area is generally from east to west down the Occidental Cordillera, often in form of steeply incised valleys. The Rio Salado drains most of the hot spring water and has its headwaters in the field where it is joined by the Rio Tucle and the Vicuna stream. Temperature measurements of the water flowing to the Rio Salado have yielded values of, while the discharge of the Rio Salado amounts to. The Rio Salado eventually joins the Rio Loa, a major source of freshwater for the region; thus, El Tatio plays an important role in the regional water supply. In the early 20th century there were several hydraulic engineering projects at El Tatio, aiming either to use its waters or to mitigate its impact on downstream water quality.
Geothermal field
El Tatio is well known as a geothermal field in Chile, and is the largest geyser field in the Southern Hemisphere with about 8% of all geysers in the world. Only the fields at Yellowstone in the United States and Dolina Geizerov in Russia are larger. They also have taller geysers than at El Tatio, where geyser fountains are on average only high. Together with Sol de Mañana, which is just east of El Tatio in Bolivia, it is also the highest-altitude geyser field in the world.The geothermal field covers an area of at elevations of, and is characterized by fumaroles, hot springs, steam vents and steaming soil. Stronger geothermal activity is located within three discrete areas covering a total of surface, and includes boiling water fountains, hot springs, geysers, mudpots, mud volcanoes and ; further, chimneys of extinct geysers have been noted. One of these three areas lies within a valley, the second on a flat surface and the third along the banks of the Rio Salado. The first area offers a notable contrast between the snow-covered Andes, the coloured hills that surround the field and the white deposits left by the geothermal activity. Most geysers of El Tatio are found here and are particularly noticeable in cold weather. A similar landscape exists at the third area, with the presence of the Rio Salado river adding an additional element to the landscape. The second area is located between a creek and a hill and includes an artificial pool for tourists. Its vents often have higher discharges than others in the field.
About 110 documented geothermal manifestations have been documented at El Tatio, but the total has been estimated at 400. The field once numbered 67 geysers and more than three hundred hot springs. Many vents are linked to fractures that run northwest–southeast or southwest–northeast across the field. Some geyser fountains in the past reached heights greater than ; usually, however, they do not exceed and their activity sometimes varies over time. A few geysers have received names, such as Boiling Geyser, El Cobreloa, El Cobresal, El Jefe, Terrace Geyser, Tower Geyser and Vega Rinconada. Minor eruptions of the geysers occur approximately every dozen minutes and major eruptions every few hours on average, and major eruptions take place after the conduit was "prepared" by multiple smaller ones. The terrain surrounding a geyser tilts as it recharges and discharges. An additional geothermal system lies southeast of and at elevations above El Tatio and is characterized by steam-heated ponds fed by precipitation water, and solfataric activity has been reported on the stratovolcanoes farther east.
Deposition of sinter from the waters of the geothermal field has given rise to spectacular landforms, including, but not limited to mounds, terraced pools, geyser cones and the dams that form their rims. Small-scale features include cones, crusts, mollusc-shaped formations, waterfall-like surfaces and very small terraces. These sinter deposits cover an area of about and include both active and inactive deposits, both of which were emplaced on glacial sediments. High contents of silica give the waters a blueish colour, organic compounds such as carotenoids conversely often colour the sinter with orange-brown, and greenish hues are owing to iron-oxidizing bacteria. Sinter accumulation is so rapid that debris and microbes can become entrapped and preserved in the sinter. Owing to the dry climate, the sinter deposits are subject to only little erosion.
Individual vent types and deposits found at El Tatio include:
- Hot springs form pools with water temperatures of, which are often gently moving and surging and in the case of the warmer springs actively bubbling. These pools often contain ball-like rocks called oncoids and are surrounded by sinter rims, which have spicule-like textures. These sinter rims often form dam-like structures around deeper vents which are filled with water. Spherical grains develop in the hot springs as a consequence of hydrodynamic processes, and include biogenic material; during the growth of the sinter they often end up embedded in the material.
- Water draining from the springs deposits sinter, which can form fairly thick deposits and large aprons when sheet flow occurs, known as "discharge deposits"; sometimes terraces are developed instead. As in springs, oncoids and spicules are observed in channels. Much of the water evaporates and its temperature drops from to less than away from the springs; the low air temperatures cause it to freeze occasionally, resulting in frost weathering.
- Geysers and also water fountains discharge from up to high cones with gently sloping surfaces, which sometimes support splash mounds. The cones are made out of geyserite. Other geysers and fountains instead discharge from within rim-bounded pools, and some geysers are in the bed of the Rio Salado river. The activity of geysers is not stable over time; changes in water supply or in the properties of the conduit that supplies them can cause changes in their eruptive activity. Such changes can be triggered by rainfall events or earthquakes and at El Tatio geyser behaviour changes have been linked to the 2014 Iquique earthquake and a 2013 precipitation event. The water of geysers is hot.
- Mud pools are often bubbling, with the hot mud fountaining. They are mainly found at the edges of the geothermal field and often produce highly acidic water; it converts rocks to clays. Simmering pools of water have been recorded at El Tatio as well.