Tephra stratigraphy of Misti volcano, Peru

Misti volcano in Peru has produced many pyroclastic falls and flows over th e last 34,000 yr. Three groups are distinguished within the pyroclastic str atigraphy. The first group is composed of a few mica-bearing, rhyolitic pyr oclastic fall and flow deposits older than 34,000 yr BP, which represent th e oldest pyroclastic deposits attributed to Misti. The second group consist s of several mica-bearing, dacitic fall deposits erupted between 34,000 and 31,200 yr BP. The third group is made up of several tens of amphibole- and pyroxene-bearing, andesitic pyroclastic-fall and Row deposits. Most deposi ts of this latter group were erupted bt tween 31,200 and 24,840 yr BP. a fe w others between 24,840 and 10,670 yr BP, and the last at 1920 pr BP. Most fallout deposits represent plinian and subplinian eruptions of less than 1 km(3) (DRE). Mineral assemblages and major-element compositions define a hi gh-K calc-alkaline series, while Sr (> 400 ppm) and Y (< 18 ppm) contents a re typical of adakitic magmas. The city of Arequipa (700,000 population) is located 17 km from, and 3500 m lower than, Misti. The four primary volcani c hazards fur Arequipa include ash and pumice fallout, pyroclastic flow, la har, and debris avalanche. Those points emphasise the fact that Misti must be considered a high-risk volcano and deserves more interest than it has re ceived to date. (C) 2001 Elsevier Science Ltd. Ail rights reserved.