Chachani 2.85

Chachani is the highest of the mountains near the city of Arequipa in southern Peru.As a result of the very low precipitation in the Arequipa area, Chachani does not have a permanent ice cap or glaciers. Climbing Chachani is popular, and many tour agencies in Arequipa offer guided trips to the summit, though the altitude is considered highly challenging for those who are not fully acclimatized.GeologyBetween six and eight separate craters form the massif of Chachani. Erosion has only left one recognizable crater in the western part of the complex. This structure has an arcuate shape. A shield thick with a diameter of is formed from coalescent lava flows on Chachani's southern side and is known as Pampa de Palacio or Las Cortaderas. An escarpment on the eastern side of Chachani may be part of a "Chachani" caldera, the source of several ignimbrites in the Arequipa area. Vegetation cover above altitude is scarce. Chachani is the eighty-four highest summit of the Andes.Chachani is largely Quaternary in origin, Cerro Nocarane and the Penones lava dome predate the ice ages. Activity of Chachani has migrated southward, from the Nocarane-Chingana volcanoes in the north to a complex of lava flows and lava domes in the south. Volcanic activity in the area began as Tacaza volcanics during the Miocene. During the Sillapaca phase starting in the Pliocene the cone building volcanism took place. By its end explosive eruptions generated voluminous rhyolitic tuffs named sillar.Several ignimbrites in the Arequipa area appear to have been erupted from beneath Chachani. This includes the 18- Arequipa Airport Ignimbrite and 16- La Joya Ignimbrite. These Pliocene ignimbrites are dated 1.64 ± 0.07 mya and 4.87 ± 0.02 mya. The eruption of these ignimbrites would have left a caldera, now completely buried beneath the Chachani complex. The 1.02 ± 0.09 mya Rio Yura tuffs were probably erupted from beneath Nocarane.