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MISTI Misti, a symmetrical cone of considerable scenic beauty immediately NNE of the city of Arequipa, has two concentric summit craters (SC). The outer crater has a maximum diameter of ~930m within which a 550m diameter scoria-rimmed inner crater is nested (Hantke & Parodi, 1966). This inner crater is slightly eccentric and merges with the eastern wall. The edifice is dissected on its NW flanks but is otherwise intact. On the lower flanks of the volcano the ash-mantled terminations of youthful lava flows (e.g. L) are discernible, but the upper flanks are covered in a dark airfall deposits which may have accompanied the formation of the scoria rim of the inner crater. Much of the flat lying plain to the northeast of the volcano is mantled by dark tephra, probably carried by the prevailing south-westerly winds. Funnelling of winds between Misti and the mountain to the east (Cerro Tacune) and transport of tephra has led to the development of an impressive parabolic dune field (PD) extending for up to 20 km downwind. Misti has been active numerous times since historic records began. The last strong eruption of Misti is thought to have occurred between 1438 and 1471 (McLelland et al., 1989). Many other eruptions have been reported since the mid-15th century. The most recent activity reportedly took place from May to October, 1948, during which the scoria deposit may have formed (Hantke & Parodi, 1966). There are reports of high temperature (>250 ?C) fumarolic activity (Hantke & Parodi, 1966. A small lava dome appears to have been present within the inner crater on photographs taken in 1959.
CHACHANI Nevado Chachani is a collection of spatially related volcanic vents covering an area of ~360 km2, located about 20 km north of the city of Arequipa (pop. ~ 900,000). It consists of three main structural elements: (1) the pre-Holocene Cerro Nocarane (CN) and dome, Cerro Los Pe��s (CP), in the north, (2) the younger Nevado Chachani (C), an arcuate volcanic ridge in the central part of the complex, and (3) a large mass of lava , the Pampa de Palacio (Las Cortaderas in Bullard, 1962), in the south (PP). Post-glacial activity appears to be confined to the latter two elements . Thin lava flows (L) from the central and western portions of Nevado Chachani overlie moraines and a well defined summit crater (SC) is present on the westernmost cone of Chachani. A small ash cone, Cerro La Horqueta (H), may represent the last activity from Cachani. Activity then migrated southwards to the Pampa de Palacio, which represents the youngest activity from the Nevado Chachani. Here, several eruptions have given rise to numerous short, thick, stubby lava flows forming a domical mass some 8 km in diameter and about 1 km thick. Notwithstanding the fact that these flows occur at lower elevations and therefore may have been better preserved than those at the higher, wetter elevations on Chachani, they are pristine and display excellent levand ridge morphologies. Extrusion of a passive dome-like mass on which two vents can be discerned appears to have been the last phase of activity.
COROPUNA This edifice is the largest and highest volcanic construct in Peru. It rises from a base level at about 4,500 m to form an elongate ridge which consists of at least 6 cones distributed over a 20 x 12 km area. Its highest point (6,377 m) is located at the northwest extremity. The light blue area on the TM image (Figure 1.1; 1.2) , obscuring much of the edifice, is a large permanent ice cap occurring above 5,300 m on the northern flank and above 4,800 m on the southern flank and covering ~130 km2 . Only minor valley glaciers are discernible on the modern volcano, but large glacial valleys (GV) and lateral moraines attributable to the ~10,000 yr BP glacial regression are prominent on all sides up to 10 km from the volcano and below heights of 4,500 m. No historic activity is known from Coropuna and the youngest apparent activity is expressed by several pristine lava flows (L), extending out several kilometers from the northeastern, southeastern, and western flanks of the edifice. These are Holocene; they occupy glacial valleys and overlie the 10,000 yr BP moraines, and their morphology and preservation suggests that they are young. This is consistent with the observations of Venturelli et al. (1978). Coropuna is one of a chain of volcanoes extending WNW-ESE, from the inactive Nevado Solimana in the west to Sabancaya in the east. This trend is paralleled by a number of young faults which are prominent on satellite images (Figure 1.2). These are best developed on the SW flanks, where Holocene normal fault displacements of at least tens of meters are conspicuous in the displacement of older lavas and stream beds.
TRADITIONAL AREQUIPA 04 days/ 03 nights
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