Laguna Miscanti is a brackish lake in the Altiplano of the Antofagasta Region in Norte Grande, Chile. It has an area of about and the shape of an arrowhead. The lake has no permanent surface inflows or outflows apart from several springs, and is primarily fed and drained by groundwater flows. Laguna Miscanti is located among the volcanoes of the Central Andes. The smaller Laguna Miñiques lies immediately south, separated from Miscanti by a lava flow.
The lake formed through tectonic processes about 22,000 years ago. During the late Pleistocene, the wetter climate of the Central Andean Pluvial Events caused Laguna Miscanti to grow, possibly until it merged with Laguna Miñiques. During the Holocene, the climate became drier again, and Laguna Miscanti shrank and may have dried out completely, leaving wetlands behind. 3,400 years ago the lake reformed and has persisted since.
Laguna Miscanti is an important breeding site for birds and a major tourist destination within the Los Flamencos National Reserve. Prehistoric peoples used the area as a hunting ground, and several archaeological sites have been identified nearby.
Etymology
The word Miscant, meaning "toad", comes from Kunza, a language formerly spoken in the Salar de Atacama and the Loa River valley. Alternate spellings are Miskanti or Miscanter. Miscanter might be the correct Kunza name and Miscanti a Quechua-language form of the name.
Overview
Laguna Miscanti is in the Central Andes, southeast of the Salar de Atacama salt flat within Chile's Antofagasta Region. The closest towns are Socaire and San Pedro de Atacama, and away, respectively. Miscanti is shaped like an arrowhead with a peninsula jutting from the northern shore. A road departs from the Paso Sico international road to Laguna Miscanti, where there are several footpaths.
With a surface area between depending on meteorological conditions, Miscanti is one of the largest water bodies of the Atacama Altiplano. The maximum depth is with the lake floor dropping steeply in the west, more gently in the east and south, and a lava flow dividing the otherwise flat bottom into two basins. There are no streams feeding into Laguna Miscanti, but several dry valleys enter from the north, east and south, and there are two springs in the bays adjacent to the peninsula. The water is clear and brackish, with little or no current. Most water comes from the Cordon de Puntas Negras mountains and reaches Laguna Miscanti underground; this groundwater supply explains why the lake persists year-round, although the role of local climatic conditions is less certain.
The lake has no surface outflow and most water leaves Laguna Miscanti through evaporation, making it a closed basin. Some water drains underground into Laguna Miñiques ( to the south and lower in elevation) and possibly to Salar de Atacama. The removal of salts through this outflow prevents Miscanti from becoming a salt pan. The lake produces banded muddy sediments consisting of fossil charophyte and diatom remnants, salts and volcanic tephra.
A low ridge, probably of Pleistocene age, separates Miscanti from Miñiques. West of the lake is the Chuculaqui or Miscanti Ridge. The surrounding terrain is covered by lake sediments, including calcarenite, diatomite, gravel and sand. Former shorelines occur at distances approaching from the present-day lake shore.
Palaeolake In the past, Laguna Miscanti was more than twice as large as it is today, covering an area of . Its water levels were about higher than today, reaching an altitude of , and may have merged with Laguna Miñiques or formed a lake chain with it. During former episodes of maximum water level (highstands), Miscanti overflowed into the Pampa Varela basin south-southwest of Miñiques, where former shorelines are visible. The lake submerged alluvial fans and left behind beach terraces, lake sediments and wave-cut platforms. The sediments consist of stromatolithes, sand, pyroclastic rocks, gravel, diatomites and calcarenites. The sediment sequence at Miscanti resembles that at Miñiques, Lejia and Tuyajto, and was deposited at a rate of about , eventually reaching a thickness of in sediment cores.
There was more life in the lake during the highstand: Algal bioherms and stromatolithes grew in the water and along the shores. Fossils indicate the presence of the green algae Botryococcus patagonicum, Botryococcus pila and Pediastrum integrum, and of Ranunculus plants.
Geology and geomorphology
The catchment of the lake consists mainly of volcanic and sedimentary rocks ranging from Miocene to Holocene age and covers a surface area of . The catchment contains several Quaternary volcanoes rising to . Among these are Cerro Miscanti () and Cerro Miñiques () northeast and south of the lake, respectively. The volcanoes are part of the Andean Volcanic Belt, created by the subduction of the Nazca Plate under the South American Plate.
The region is characterized by north-south-trending mountain chains, which separate various basins occupied by salt flats or lakes. The lakes Laguna Lejia, Laguna Miscanti and Laguna Miñiques occupy basins formed by the Pliocene and Pleistocene reactivation of the Quebrada Nacimiento fault west of Laguna Miscanti. The fault extends from the Purico complex at Llano de Chajnantor to Cerro Miñiques, and is one of the most important faults in the region. Groundwater flow into and out of Laguna Miscanti occurs along the Quebrada Nacimiento fault.
The Quebrada Nacimiento fault is part of a larger fault system, variously described as a detachment or thrust fault system, separating the Western Cordillera from the Cordillera Domeyko. The volcanoes Lascar and the Cerros Saltar and Corona north and south of Lascar are situated on the fault, they possibly formed under its influence. The Miscanti Ridge also formed through activity on this fault.
Climate
There are no long-running weather records from Laguna Miscanti. The climate is cold, with average annual temperatures of , being slightly higher at the lake than in the surrounding region. Temperatures vary sharply between day and night, reaching lows of during the night; seasonal variations reach only . Days are usually clear and sunny. Parts of the lake surface freeze over during winter.
The region features a dry-winter cold semi-arid climate bordering on tundra, according to the Köppen climate classification. The annual evaporation rate of vastly exceeding the average precipitation of .
The region's aridity results from the Andes rain shadow, the cold Humboldt Current in the Pacific Ocean, and the subtropical anticyclone. Most precipitation falls during austral summer (December–February) during the so-called "Bolivian Winter", but winter precipitation is significant. Depending on the season, it is brought by the summer monsoon, weather fronts or cut-off lows but its ultimate origin is the Amazon. The El Niño-Southern Oscillation pattern of climatic variability influences precipitation in the Altiplano, being usually higher at Laguna Miscanti during La Nina events when more Amazon moisture reaches the area.
Geologic history
Laguna Miscanti may have formed 22,000 years ago, when tectonic and volcanic activity trapped water in the future lake basin. Soon after forming, the lake reached its first highstand. At some point during the Pleistocene, a lava flow from Cerro Miñiques formed the barrier separating Miscanti and Miñiques. During the Last Glacial Maximum, conditions became colder and drier than the present-day, leading to a total disappearance of vegetation and a drying of the lake between 22,000 and 14,000 years ago.
In the Late Glacial/late Pleistocene and early Holocene the climate of the Atacama and Central Andes was much wetter (Central Andean Pluvial Event [CAPE] or "Tauca phase") and precipitation nearly doubled in the southern Atacama. Vegetation extended into the Atacama and lakes formed (Lake Tauca) or grew in size until the water-covered area in the region had reached 5–10 times that of present-day water bodies. Researchers divide this humid interval into two phases: the wetter Tauca or CAPE I (17,50014,200 years before present) and Coipasa or CAPE II (13,8009,700 years before present), which are not entirely synchronous between the Atacama and the Altiplano. The second highstand of Laguna Miscanti took place during CAPE II. Pollen data indicate that a stronger easterly wind was responsible for the highstand at Miscanti.
The Holocene brought a more stable, warmer and drier climate to the central and south-central Andes which caused the lakes to shrink. Miscanti became hypersaline as water levels dropped by about . It may have dried up completely, forming a bog or a mudflat surrounded by wetlands that attracted camelids like guanacos and vicuñas. The dry period was caused by decreased insolation caused by the Milankovich cycles weakening the monsoon. A widespread abandonment of archaeological sites, the "archaeological silence", coincides with the drought, although Miscanti itself remained inhabited during that time. The exact chronology of the dry period depends on the site; in the case of Laguna Miscanti, there are uncertainties caused by issues with radiocarbon dating, and some places might have been wetter during the middle Holocene.
Occasional storms caused floods even during the dry period, and there were short (yearly to centennial) wet periods that are not always recorded in the lake. The late Holocene saw renewed wetness in the region; at Miscanti the dry period definitively ended after about 4,000 years ago through several pulses of moisture, and human resettlement at Laguna Miscanti took place about 3,400 years ago. The lake reformed 3,600 years ago and has persisted since then. More recent fluctuations include a dry period beginning 1650 AD and ending either 1850 or 1920 AD, perhaps linked to the end of the Little Ice Age. Between 1980 and 2000 water levels were approximately stable, then decreased until about 2015 when another upward trend began. Such variability is consistent with the behaviour of other high-altitude lakes in northern Chile, which have largely escaped the effects of the Chilean megadrought.
Biology
Aquatic plants like Myriophyllum and charophytes like Chara grow on the lake floor; Chara globularis meadows cover most of the lake floor. Aquatic fauna include amphipods, branchiopods (Chydorus sphaericus), cladocerans (Alona pulchella), copepods (Boeckella poopoensis, the main crustacean in the lake and in other water bodies of the region) and ostracods (Hyalella fossamanchini and Hyalella kochi). The existence of the cladoceran daphnids is uncertain. Microorganisms living in the lake waters include bacteria and ciliates; fossils of diatoms and the ostracod Limnocythere sappaensis occur in the sediments of Laguna Miscanti.
The beaches and alluvial cones of Laguna Miscanti feature meadows consisting of Fabiana, Festuca, Ruppia and Stipa chrysophylla. Sparser vegetation known as "tolar" grows on the surrounding terrain. It is dominated by grasses, along with bushes and perennial herbs; species include Baccharis, ichu and yareta. Above elevation, vegetation disappears and the landscape transitions to high-altitude desert. Vegetation composition has been stable during the Holocene.