Laguna Miscanti

Laguna Miscanti is a brackish water lake located in the altiplano of the Antofagasta Region in northern Chile. Cerro Miñiques volcano and Cerro Miscanti tower over this lake. This 13.5 square kilometres (5.2 sq mi) large heart-shaped lake has a deep blue colour and developed in a basin formed by a fault. South of Miscanti lies Laguna Miñiques, another lake which is separated from Miscanti by a lava flow that was emplaced there during the Pleistocene.

The lake is part of one of the seven sectors of Los Flamencos National Reserve. A number of birds and mammals live at the lake, which is a major tourist destination.

Laguna Miscanti lies in the Central Andes^[2] of Chile,^[3] east-southeast of the Salar de Atacama. Administratively, it is part of the Antofagasta Region.^[4] The closest town is Socaire, 20 kilometres (12 mi) away from the lake.^[5] A road departing from the Paso Sico international road goes to Miscanti,^[6] which is accessible by an unpaved road and numerous footpaths.^[7]

The town of Peine draws its water supply from the Miscanti basin.^[8] The inhabitants of Socaire used the area for grazing, and it bears spiritual and religious importance for them.^[9] Laguna Miscanti and Laguna Miñiques are part of the third sector of the Los Flamencos National Reserve,^[10] and are jointly administered by the community of Socaire and by the National Forest Corporation.^[11] In 2002, there were 5,000 tourists at Miscanti and the nearby lake Miñiques,^[12] and in 2015, one in three tourists who went to the Los Flamencos National Reserve visited Miscanti and Laguna Miñiques.^[13] Laguna Miscanti is of scientific importance, as it has a record of palaeoclimatic changes going back to the last glacial maximum.^[14]

An archeological site ("Miscanti-1")^[15] has been discovered on a beach terrace at the southeastern end of the lake. It contains remnants of animals, hearths and lithic artifacts buried in volcanic ash.^[14] It was presumably a campsite used by prehistoric hunter-gatherer populations,^[16] which produced hunting tools and consumed game there.^[17]

Climate variability influenced human settlement in the region during the Holocene, which took place mainly during wetter periods^[18] when the environment became much more favourable,^[15] becoming concentrated in several environmentally favourable spaces during dry periods.^[19] At Laguna Miscanti, wetlands and areas suitable for grazing formed during the middle Holocene drought, thus the area remained hospitable for human inhabitation.^[19]

Laguna Miscanti has a surface area of 13.5 square kilometres (5.2 sq mi),^[20] making it one of the largest waterbodies of the Atacama Altiplano.^[21] The lake has the shape of an arrowhead with a peninsula jutting from the northern shore.^[3] Maximum water depths reach 10 metres (33 ft).^[20] The western lakefloor is steep, while the eastern and southern shores have gentler slopes.^[14] A lava flow separates the otherwise flat lake floor into two basins.^[22] The surrounding terrain is covered by lake sediments, including calcarenite, diatomite, gravel and sand.^[23] Former shorelines occur at distances approaching 1 kilometre (0.62 mi) from the present-day lake shore.^[14] A number of creeks^[a] enter into Laguna Miscanti from the north, east and south (Quebrada de Chaquisoqui^[1]), and there are two springs in the bays on either side of the peninsula.^[3]

The waters are clear^[14] and brackish^[b],^[20] with only weak currents if at all.^[14] The lake has no surface outflow. Presently, water seeps to Miñiques through a lava flow^[20] along the path of the Quebrada Nacimiento fault;^[25] the removal of salts through this outflow prevents Miscanti from becoming a salt pan.^[25] Most water, however, leaves Laguna Miscanti through evaporation,^[26] making it a closed basin.^[25]

The Cordon de Puntas Negras is the principal source of water.^[25] Water reaches Laguna Miscanti principally underground,^[14] which is directed there by the fault; this may explain why Laguna Miscanti is a permanent lake rather than a playa.^[27] The lake forms banded muddy^[28] sediments consisting of fossils^[c], salts^[d][25] and volcanic tephra layers^[e].^[30]

In the past, Laguna Miscanti was much larger, covering an area of 38.2 square kilometres (14.7 sq mi). Its water levels were about 29 metres (95 ft) higher than today, reaching an altitude of 4,179 metres (13,711 ft),^[14] and may have merged with Laguna Miñiques.^[25] The lake submerged alluvial fans^[31] and left beach terraces,^[20] lacustrine sediments^[f][26] and wavecut platforms.^[25] There was more biological activity in the lake during the highstand:^[32] Algal bioherms^[33] and stromatolithes grew in the water,^[25] and fossils indicate the presence of Botryococcus, Pediastrum integrum and Ranunculus plants.^[34] During former lake highstands a lake chain^[35] or a combined lake overflowed into the Pampa Varela basin^[20] south-southwest of Miñiques.^[36]

1.5 kilometres (0.93 mi) south of^[19] the lake is another waterbody, Laguna Miñiques.^[37] The barrier separating the two probably formed during the Pleistocene, when a lava flow erupted from Cerro Miñiques split the lake basin in two.^[27][38] The catchment of the lake consists mainly of volcanic and sedimentary rocks ranging from Miocene to Holocene age and covers a surface area of 320 square kilometres (120 sq mi).^[20] Quaternary volcanoes with summit elevations of 5,000–6,000 metres (16,000–20,000 ft) dot the catchment.^[5] Among these are Cerro Miscanti (5,622 metres (18,445 ft)) and Cerro Miñiques (5,910 metres (19,390 ft)) northeast and south of the lake, respectively.^[36] The volcanoes are part of the Andean Volcanic Belt, which is formed by the subduction of the Nazca Plate under the South American Plate.^[31] West of the lake is the Chuculaqui ridge.^[3]

Miscanti and Miñiques occupy fault-bound basins;^[19][20][26] the Quebrada Nacimiento fault^[25] is also known as the Miscanti Fault and is part of a detachment fault system east of the Salar de Atacama,^[39] which separates the Western Cordillera from the Cordillera Domeyko.^[26][14] This fault extends from the Purico complex,^[40] Llano de Chajnantor to Miñiques and has formed a ridge, which has dammed lava flows from Cerro Miscanti and Cerro Miñiques.^[38] The basins developed during the Pliocene and Pleistocene^[25] when the fault reactivated;^[26] Laguna Lejia also developed along this fault^[26] and the fault segment there is also known as Miscanti-Callejon de Varela fault.^[41] Volcanoes^[26] including Lascar^[42] and the Cerros Saltar and Corona north and south of Lascar formed on the fault.^[43]

There are no long-running weather records from Laguna Miscanti.^[44] Temperatures are cold, with average annual temperatures of 2 °C (36 °F), varying by about 8–10 °C (46–50 °F) between seasons.^[45] Parts of the lake surface freeze over during winter.^[20] The lake area is usually a little warmer than the surrounding region.^[46]

The region features an arid climate,^[37] with the annual evaporation rate of 2 metres per year (0.21 ft/Ms) vastly exceeding the average precipitation, which amounts to 200–250 mm/a (7.9–9.8 in/year).^[14] The aridity is due to the combined effects of the rain shadow of the Andes, the cold Humboldt Current off the coast in the Pacific Ocean and the subtropical anticyclone.^[47] Most precipitation falls during summer (December-February)^[14] but winter precipitation is significant^[g]. Depending on the season, it is brought by the summer monsoon, weather fronts or cutoff lows^[25] but its ultimate origin is the Amazon.^[48] The El Niño-Southern Oscillation pattern of climatic variability influences precipitation in the Altiplano,^[48] being usually higher at Laguna Miscanti during La Nina events.^[49]

Laguna Miscanti may have formed 22,000 years ago, when tectonic and volcanic activity trapped water in the future lake basin. At this point, the lake reached its highstand for the first time. About 18,000 years ago,^[14] the Last Glacial Maximum turned drier^[50] and colder, leading to a total disappearance of vegetation^[51] and a drying of the lake between 22,000 and 14,000 years ago.^[52]

In the late Pleistocene and early Holocene the climate of the Atacama and Central Andes was much wetter (Central Andean Pluvial Event^[53] or "Tauca phase"^[21]) and precipitation nearly doubled in the southern Atacama.^[15] As a consequence, lakes formed (Lake Tauca) or grew in size,^[54] including Laguna Miscanti where the second highstand occurred^[14] during the Late Glacial.^[26] This humid period has been subdivided into two stages,^[37] the wetter^[55] Tauca or CAPE I (17,500–14,200 years before present) and Coipasa or CAPE II (13,800–9,700 years before present), which are not entirely synchronous between the Atacama and the Altiplano.^[37][53] Pollen data indicate that a stronger easterly wind was responsible for the highstand at Miscanti.^[50]

The Holocene brought a warmer and drier climate to the central and south-central Andes which causes the lakes to dry up. Miscanti became hypersaline^[15] as water levels dropped by about 10 metres (33 ft).^[56] It may have dried up completely, forming a bog^[14] or mudflat surrounded by wetlands that attracted camelids^[14] like guanacos and vicuñas.^[57] The dry period was associated with a widespread abandonment of archaeological sites, the "archaeological silence", although Miscanti itself remained inhabited during that time.^[19] The exact timing of this dry period, which was caused by decreased insolation caused by the Milankovich cycles weakening the monsoon,^[58][59] depends on the site.^[19] Climate was more stable during the Holocene than the late Pleistocene;^[60] at Miscanti there were wet pulses on century or decade time scales,^[14] and a brief moist epoch between 6,500 and 5,000 years ago.^[61] At Miscanti, the dry period definitively ended after about 4,000 years ago^[62] through several pulses of moisture,^[63] and human resettlement at Laguna Miscanti took place about 3,400 years ago.^[64] The lake reformed 3,600 years ago and has remained since.^[14] More recent fluctuations include a dry period between 1650–1850 AD^[h], perhaps linked to the ending Little Ice Age.^[18]

The lakefloor is populated by aquatic plants,^[14] including water plant Myriophyllum^[33] and charophytes^[66] like Chara;^[33] charophytes like Chara globularis form meadows^[32][45] covering the entire lake floor.^[24] Fossils of diatoms^[25] and the ostracod Limnocythere sappaensis^[i] occur in the sediments of Laguna Miscanti,^[67] and amphipods in the lake waters.^[68]

There are meadows consisting of Fabiana, Festuca, Ruppia, Stipa chrysophylla on the alluvial cones and beaches of Laguna Miscanti. Sparser vegetation^[33][14] consisting of Baccharis species also known as "tolar", and ichu grow on the surrounding terrain,^[69] which is sometimes described as barren.^[45] Fauna that inhabits the area includes birds like flamingos,^[70] Fulica ardesiaca (Andean coot), Fulica cornuta (Horned coot), Larus serranus (Andean gull), Lophonetta speculiarioides (Crested duck) and Podiceps occipitalis (silvery grebe),^[71] and mammals like Ctenomys opimus (Highland tuco-tuco), Lagidium viscacia (Southern viscacha), Phyllotis darwini (Darwin's leaf-eared mouse), Pseudalopex culpaeus (culpeo) and Vicugna vicugna (vicuña);^[70] the two lakes are important breeding sites for the horned coot.^[72]