tectonic plate is subducting at a rate of beneath the continental part of the South American tectonic plate; this process is responsible for volcanic activity and the uplift of the Andes mountains and of the Altiplano plateau. The subduction is oblique, leading to strike-slip faulting. Volcanic activity does not occur along the entire length of the Andes; where subduction is shallow, there are gaps with little volcanic activity. Between these gaps lie volcanic belts: the Northern Volcanic Zone, the Central Volcanic Zone, the Southern Volcanic Zone and the Austral Volcanic Zone. There are about 400 Pliocene–Quaternary volcanoes in Peru, with Quaternary activity occurring only in the southern part of the country. Peruvian volcanoes are part of the Central Volcanic Zone. Volcanic activity in that zone has moved eastward since the Jurassic. Remnants of the older volcanism persist in the coastal Cordillera de la Costa but the present-day volcanic arc lies in the Andes, where it is defined by stratovolcanoes. Many Peruvian volcanoes are poorly studied because they are remote and difficult to access. The basement underneath Huaynaputina is formed by almost sediments and volcanic intrusions of Paleozoic to Mesozoic age including the Yura Group, as well as the Cretaceous Matalaque Formation of volcanic origin – these are all units of rock that existed before the formation of Huaynaputina. During the Tertiary, these were overlaid by a total of deposits from the ignimbritic Capillune, Llallahui and Sencca Formations – all older rock units. Cretaceous sediments and Paleogene–Neogene volcanic rocks form the high plateau around Huaynaputina. The emplacement of the Capillune Formation continued into the earliest Pliocene; subsequently the Plio-Pleistocene Barroso Group was deposited. It includes the composite volcano that hosts Huaynaputina as well as ignimbrites that appear to come from calderas. One such caldera is located just south of Huaynaputina. The late Pleistocene to Holocene volcanoes have been classified as the Arequipa Volcanics. Local The vents of Huaynaputina trend from the north-northwest to the south-southeast, and this trend encompasses the neighbouring volcanoes Ubinas and Ticsani. Ubinas is a typical stratovolcano while Ticsani has a similar structure to Huaynaputina. These volcanoes constitute a volcanic field located behind the major volcanic arc, associated with faults at the margin of the Río Tambo graben and regional strike-slip faults. The faults associated with the volcanic complex have influenced the evolution of the constituent volcanoes including Huaynaputina by acting as conduits for ascending magma especially at