page_title: Ollagüe
section_title: Local
hierarchical_section_title: Ollagüe / Geography and geomorphology / Local
caption_attribution_description: English: Frontera Chile-Bolivia, Volcan San Pedro, Volcan San Pablo
context_page_description: Ollagüe or Ullawi is a massive andesite stratovolcano in the Andes on the border between Bolivia and Chile, within the Antofagasta Region of Chile and the Potosi Department of Bolivia. Part of the Central Volcanic Zone of the Andes, its highest summit is 5,868 metres above sea level and features a summit crater that opens to the south. The western rim of the summit crater is formed by a compound of lava domes, the youngest of which features a vigorous fumarole that is visible from afar.
  Ollagüe is mostly of Pleistocene age. It started developing more than one million years ago, forming the so-called Vinta Loma and Santa Rosa series mostly of andesitic lava flows. A fault bisects the edifice and two large landslides occurred in relation to it. Later two groups of dacitic lava domes formed, Ch'aska Urqu on the southeastern slope and La Celosa on the northwestern. Another centre named La Poruñita formed at that time on the western foot of the volcano, but it is not clear whether it is part of the main Ollagüe system. Activity at the summit continued during this time, forming the El Azufre sequence.
context_section_description: Ollagüe is a stratovolcano and lies isolated slightly east of the main volcanic arc. The volcano is usually covered with snow, which together with yellow and red colours gives Ollagüe a "beautiful" appearance. Other than some past glacial activity, the arid climate of the Altiplano region has kept erosion rates low, meaning that the volcanic edifice is well preserved. On the other hand, lack of erosion also means that relatively little of its internal structure is exposed.
  Ollagüe has two summits, Ollagüe South is 5,868 metres (19,252 ft) high and Ollagüe North 5,863 metres (19,236 ft). The summit features a summit crater 300 metres (1,000 ft) below the summit with a narrow opening towards the south, which forms the Quebrada El Azufre. The rim of the crater culminates into 5,868 metres (19,252 ft) high Ollagüe South. The western rim is formed by several lava domes. These lava domes feature landslide deposits and lava flows that emanate from the foot of the dome. Originally they were considered to be a single lava dome, before it was found that the dome is formed by four individual domes. Just north of the summit crater lies another semicircular crater rim which encircles the summit crater on its northern side and whose high point is 5,863 metres (19,236 ft) high Ollagüe North. The northeastern part of the edifice is old and affected by glaciation and the development of gullies, while the southwestern part has experienced younger activity and flank collapses. The volume of the well exposed edifice is about 85 to 91 cubic kilometres (20 to 22 cu mi) covering a surface area of 260 square kilometres (100 sq mi). Ollagüe rises about 2,065 metres (6,775 ft) above the surrounding terrain. 
  The volcano has a number of adventive vents on its slopes, especially the northwestern and southeastern slope. These include Ch'aska Urqu on the southeastern slope and La Celosa (4,320 metres (14,170 ft); also known as El Ingenio) on the northwestern. They lie at distances of 4–8 kilometres (2.5–5.0 mi) and 1–4 kilometres (0.62–2.49 mi) from the summit vent, respectively. The alignment of these subsidiary vents with the summit vents suggests that a N55°W striking lineament influenced their eruption; such channelling of magma along radial fractures has also been observed on other volcanoes such as Medicine Lake volcano, Mount Mazama and South Sister. A normal fault runs across the main edifice but is not aligned with these adventive vents, and the Pastos Grandes-Lipez-Coranzuli lineament intersects with the volcanic arc at Ollagüe. Fault scarps are found on the northwestern and southeastern side of the edifice. Overall, northwest trending lineaments exercised a strong influence on the tectonic development of Ollagüe, and may be the path that feeder dykes of the more recent eruptions followed. The basement undergoes extension perpendicularly to the lineament.
  A 700 metres (2,300 ft) wide phreatomagmatic vent named La Poruñita lies on the western slope, on the deposit formed by the sector collapse. It lies at an elevation of 3,868 metres (12,690 ft), is constructed out of tephra and formed on the sector collapse deposit. Farther up on the edifice, two cinder cones are found just north and west of the highest summit of Ollagüe.
  Ollagüe has experienced glacial activity. Moraines are found on top of young lava flows and glacial valleys cut into the slopes. On the western side, there are remnants of a moraine girdle, which reaches an elevation of 4,500 metres (14,800 ft) on the southwestern foot of the volcano. Another possibly separate moraine girdle has been reported in the summit region, at elevations of about 5,000 metres (16,000 ft). This moraine is thought to have been formed during the Little Ice Age; the present-day snowline is higher than the volcano, while the Pleistocene one may have occurred at elevations of 5,000 metres (16,000 ft).
  Areas of hydrothermal alteration are found on Ollagüe, including in the summit crater, on its northeastern and northwestern rim and low on the northwestern slope. Alunite, gypsum and sulfur were formed by th
caption: Map of the region
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