Ticsani is a volcano in Peru. It consists of two volcanoes that form a complex: "old Ticsani", which is a compound volcano that underwent a large collapse in the past and shed of mass down the Rio Tambo valley; the other is a complex of three lava domes which were emplaced during the Holocene. The last eruption occurred after the 1600 eruption of neighbouring Huaynaputina.
Geography and geomorphology
Ticsani is in the Ichuna District of Peru, northwest of Moquegua. The Putina River passes northwest and the Carumas River southwest of the volcano. The area is remote, which has hampered exploration efforts. There are paved roads in the area, which can be accessed mainly through the Ilo-Desaguadero highway. Volcanism in South America occurs along its western coast and in several volcanic belts, including the Central Volcanic Zone that Ticsani is part of. In southern Peru the Central Volcanic Zone includes the volcanoes Solimana, Coropuna, Ampato, Sabancaya, Chachani, El Misti, Ubinas, Huaynaputina, Ticsani, Tutupaca, Calientes, Yucamane, Purupuruni and Casiri. Ticsani features three lava domes, which were generated by latest Pleistocene and Holocene activity; two of which are located within or at the margins of craters. An earlier compound volcano is today preserved as a long arcuate ridge, which is northeast of the northernmost dome and opens to the west; a cryptodome is exposed within the arcuate ridge. The complex reaches a height of. The position of the lava domes and the structure of the compound volcano were influenced by local fault systems.
Geology
Off the southwestern coast of South America, the Nazca Plate subducts beneath the South America Plate in the Peru-Chile Trench, at a rate of. This subduction process is responsible for the growth of the Andes and for volcanism in the region; the oblique character of subduction has further led to the onset of strike-slip faulting. Ticsani is grouped together with the neighbouring volcanoes Huaynaputina and Ubinas, given their tectonic context, which is unusual for Peruvian volcanoes and shared geochemical traits. Huaynaputina had a large eruption in 1600 and Ubinas is presently the most active volcano in southern Peru. These volcanoes appear to share a magma chamber at a depth of. The basement on which these volcanoes rose includes a Paleoproterozoicpluton. It is covered by the Mesozoic Yura Group and Matalaque Formation which are exposed at the Rio Tambo. Volcanic activity continued during the Miocene, Pliocene and Pleistocene, forming ignimbrites and the Barroso Group.
Ticsani was active during the Pleistocene and Holocene. At first, a compound volcano developed at Ticsani. This volcano collapsed and formed a landslide deposit in the Rio Tambo valley which originally had a volume of about, and is thus the largest such collapse in southern Peru during the Pleistocene. This volcano stage is also known as "old Ticsani", separate from the lava dome associated "new Ticsani". Later three lava domes were emplaced and three explosive eruptions took place, accompanied by the emission of volcanic ash, blocks, lava bombs and pumice. The first eruption with a tephra volume of about happened at 10,600 ± 80 years before present, the second in the middle Holocene and the last sub-Plinian to phreatomagmatic eruption took place shortly before the Huaynaputina eruption of 1600, generating about of tephra. This volcano stage also produced lava flows which filled valleys, formed a lava flow field northwest of the volcano and pyroclastic flows on the eastern side of the volcano. Presently, hot springs are found in the valleys west of Ticsani, and two fumaroles have been observed at its summit. The Putina River hot springs are among the most important in Peru. In 2005, earthquake activity was noted beneath Ticsani, possibly related to a hydrothermal system, which raised alarm and concern among the local population. A temporary seismic station installed 2015 at Ticsani recorded volcano-tectonic earthquakes, and other changes in its behaviour have been observed as well.
Hazards
About 5,000 people live within to Ticsani and would be threatened in the case of a future eruption, with particular hazards including ash fall, lahars, pyroclastic flows and the collapse of lava domes. In addition to the local population, ashfall would hit major regional roads and reservoirs. Towns in the area include Calacoa, Cambrune, Carumas, Quebaya, San Cristobal and Soquezane. The volcano is classified as being a "High Risk Volcano". In 2015, facilities to monitor the chemical composition of hot springs around the volcano were installed, and devices to recognize deformations of the volcanic edifices are installed. The Peruvian Southern Volcanological Observatory publishes monthly reports on Ticsani since 2014, which include reports on seismic activity and on sulfur dioxide emissions.
