Tumisa
| Tumisa | |
|---|---|
| Cerro Tumisa | |
 Tumisa
|
|
| Highest point | |
| Elevation | 5,658 m (18,563 ft) |
| Coordinates | 23°28′S 67°49′W / 23.467°S 67.817°WCoordinates: 23°28′S 67°49′W / 23.467°S 67.817°W |
| Geography | |
| Parent range | Andes |
| Geology | |
| Age of rock | |
| Mountain type | Stratovolcano |
| Volcanic belt | Central Volcanic Zone |
| Last eruption | 500,000 years ago |
Tumisa (also known as Cerro Tumisa) is a stratovolcano in the Andes. Located east of the Salar de Atacama, it is part of the Central Volcanic Zone, which since the Miocene has been subject to extensive andesitic/dacitic effusive activity and ignimbrite eruptions. The basement on which Tumisa is built includes Paleozoic rocks and more recent volcanic products of the Lejia volcano and the Atana and Patao ignimbrites.
Block flows, lava flows, lava domes and some ignimbrites of pumiceous composition form this composite volcano. More than six lava domes and two major cones are part of this system and surrounded by a pyroclastic apron, which covers a surface area of 300 square kilometres (120 sq mi) and is formed from many pyroclastic flows with a total volume of 21 cubic kilometres (5.0 cu mi). The pyroclastic flows contain pumice and large blocks, some of which show signs of deformation when they were still hot. The lava domes and lavas are grouped in three units. Presumably, the activity of Tumisa started with explosive eruptions that generated the ignimbrite apron, later degassed magma formed the lava domes and lava flows.
Dating of the volcano indicates that it becomes younger with higher altitude, a pattern that may be explained either by a shift in the magmatic system or a progressive downslope sliding of the volcano during its history at a speed of 0.5–2 centimetres per year (0.20–0.79 in/year). This interpretation is supported by the drainage patterns of the volcano, with channels bending outwards and curving towards the west. These channels possibly formed over faults of the slipping volcano. Valleys (quebradas) were excavated less than one million years ago during the glacial stages in Tumisa's northern flank. Moraines are also found.
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