Olca-Paruma (also Olca-Michincha) is a series of stratovolcanoes on the border of Chile and Bolivia. The ridge spans and trends from east to west. Four major volcanoes comprise the group; from east to west, they are Cerro Paruma , Paruma volcano , Olca , and Michincha .
Except for Paruma, all of the volcanoes have erupted during the Holocene. Lava flows have been found extending from the volcanoes, including one series from Olca Sur. Paruma has been active historically, is covered by several young lava flows, and has continued fumarolic activity. Only one recorded eruption has taken place within the range: between 1865 and 1867, an explosive eruption took place from an alternate vent of one of the volcanoes.
Olca is comprised by a base overlain by early lava flows, and has a visible summit crater. The volcano was heavily glaciated along its southern flank. Paruma erupted two extensive lava flows, as well as one short one that suggests the volcano's lava is more mafic than that of its neighbours.
Like all South American volcanoes, the Olca-Paruma complex was formed by subduction of the Nazca Plate under the South American continental plate. It is one of 53 Holocene volcanoes located in northern Chile, Argentina, and Bolivia.
On November 13, 1989, policemen in Ujina noted seismic activity caused by fumaroles at Olca volcano. In March 1990, a geologist at Empresa Nacional del Petróleo reported a weak earthquake by the volcano. However, there is no known hazard from any of the volcanoes.