Olca
From Wikipedia, the free encyclopedia
Olca is a stratovolcano on the border of Chile and Bolivia. It lies in the middle of a 15 km long ridge composed of several stratovolcanos. Cerro Minchincha lies to the west and Paruma to the east. It is also close to the pre-Holocene Cerro Paruma. It is andesitic and dacitic in composition, with lava flows extending several kilometres north of the peak. The only activity from the ridge during historical times was a flank eruption from 1865 to 1867. The exact source of this eruption is unclear.
| Olca | |
|---|---|
| |
| Highest point | |
| Elevation | 5,407 m (17,740 ft) |
| Coordinates | 20°56′0″S 68°29′0″W |
| Geography | |
  Olca | |
| Location | Bolivia, Nor Lípez Province, San Pedro de Quemes Municipality, Cana Canton Chile, Antofagasta Region, El Loa Province |
| Parent range | Andes |
| Geology | |
| Mountain type | Stratovolcano |
| Last eruption | 1867 |
Gas emissions and composition
The gasses emission is comprised by a single warm spring at the base[1] and a persistent fumarole field over at the crater's dome for at least 60 years.[2] The fumarolic field is about 0.1 km2 and the emissions measured in situ at the crater show a highly mixed magmatic system between high temperature gasses and hydrothermal fluids.
The gas composition indicates low concentration of H2, CO and acidic gasses, and high concentration of H2S and hydrocarbons.[2] The carbon/sulfur ratios are high and the isotopic values suggest the mixture between magmatic, hydrothermal, and atmospheric fluids.[2] Other techniques used to measure the amount of SO2 includes remote sensing techniques called Differential Optical Absorption Spectroscopy(DOAS) giving maximum concentration of 35 ppm.m of SO2;[3] and the most recent taken with a UV camera suggesting an average of 18.4 t d−1.[4]
Eruptive history and latest activity
Different information exists regarding the activity and activity migration of Olca. There is a study dating two flows, which suggest a formation during the Pleistocene,[5] while others suggest to be much older with the appearance of the edifices volcanic activity migrated east over time.[6] There is also evidence that glaciers were on the volcano in the late Pleistocene.[6] The
Unconfirmed historical eruptions are suspected to have occurred in 1865–1867.[7] The last activity has been reported of low-intensity seismicity accompanied with fumarolic activity in November 1989 and March 1990 intense degassing.[8] In 2010, there a campaign conducted seismic activity showing 3 potencial swarms without a clear interpretation.[7]
