Socompa
| Socompa | |
|---|---|
Socompa as seen from the Salar de Atacama.
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| Highest point | |
| Elevation | 6,051 m (19,852 ft) |
| Prominence | 2,015 m (6,611 ft) |
| Listing | Ultra |
| Coordinates | 24°23′45″S 68°14′45″W / 24.39583°S 68.24583°WCoordinates: 24°23′45″S 68°14′45″W / 24.39583°S 68.24583°W |
| Geography | |
 Socompa
Location in Argentina, on the border with Chile
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| Location | Argentina - Chile |
| Parent range | Andes |
| Geology | |
| Mountain type | Stratovolcano |
| Last eruption | 5250 BCE (?) |
| Climbing | |
| First ascent | 1919 |
| Easiest route | glacier/snow |
Socompa is a large complex stratovolcano at the border of Argentina and Chile. It is best known for its large debris avalanche deposit, which is widely accepted as the best-preserved example of this type of deposit in the world, and also notable as the home of the world's most elevated known microbial ecosystems.
The western rim of the volcano borders the Monturaqui Basin, which is draped with the aforementioned deposit. Escondida Mining currently has a network of roads throughout this area, from beneath which they pump ground water for use at the nearby copper mine. The southern margin of the deposit is bordered by the Antofagasta to Salta trans-Andean railway, although this is rarely used.
The volcano is difficult to reach - either from the north along dirt tracks south of the Miscanti Pass, or from the west via the Escondida copper mine. Both routes require a full-day's driving and for any reasonable amount of time to be spent at Socompa would need significant planning.
The Socompa deposit contains many features that are expected from a debris avalanche, including large-volume, rotated and slumped toreva blocks and hummocky topography. There is also evidence for a magmatic component (Bezymianny-type collapse) from the breadcrust texture of large dacitic blocks and a thin pyroclastic flow deposit. A large amphitheatre, open at 70° and 10 km wide at its mouth, marks the site of collapse on the remaining edifice. Since the failure, which occurred some 7000 years ago, this has been partially filled by subsequent lavas and pyroclastics.
The deposit's most striking aspects are its volume, deposition and composition. It has a volume of 25 km2 (10 sq mi)—around an order of magnitude greater than the Mount St. Helens collapse—in addition to 11 km2 (4 sq mi) of toreva blocks at the mouth of the amphitheatre. These dimensions set it apart from most other known terrestrial debris avalanches.
While a significant component of the deposit clearly originates from the ancestral Socompa edifice, there are also large amounts of ignimbrite and gravels which have been shown to have come from the substrata immediately below Socompa, and which make up the bulk (80%) of the deposit by volume. Despite originating at the lowest part of the failure zone, these units travelled the furthest distance and are found at the base of the deposit. The avalanche travelled down the regional slope for part of its course before mounting at least 250 m (820 ft) of topography near to its distal end, suggesting a high speed of emplacement, low friction and great mobility. There was also considerable remobilisation of the deposits and secondary flowage after the initial deposition, creating the lobe which was channeled northwards under gravity towards the Monturaqui Basin.
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Wikipedia