The late Pleistocene Sacarosa tephra-fall deposit, Misti Volcano, Arequipa, Peru: its magma, eruption, and implications for past and future activity

• Autores: Harpel, Christopher J., Cuno, Juan José, Takach, Marie K., Rivera, Marco, Aguilar, Rigoberto, Tepley III, Frank J., Garcia, Fredy
• Formato: artículo
• Fecha de Publicación: 2023
• Institución: Instituto Geofísico del Perú
• Repositorio: IGP-Institucional
• Lenguaje: inglés
• OAI Identifier: oai:repositorio.igp.gob.pe:20.500.12816/5453
• Enlace del recurso: http://hdl.handle.net/20.500.12816/5453; https://doi.org/10.1007/s00445-023-01654-z
• Nivel de acceso: acceso abierto
• Materia: Misti volcano; Cayma stage; Plinian eruption; Tephrostratigraphy; Magma conditions; Dacite; https://purl.org/pe-repo/ocde/ford#1.05.07

Between 38.5 ka cal BP and 32.4 ka cal BP, a dacitic Volcanic Explosivity Index 5 eruption at Misti volcano emplaced the Sacarosa tephra-fall deposit. Its biotite phenocrysts, fine grain size, scarce lithics, and abundant loose crystals characterize the deposit at locations sampled. The eruption’s ~ 800 °C magma rose rapidly from ~ 10 km depth, culminating in a Plinian eruption which reached a mass eruption rate of 7.7 × 10⁶–4.1 × 10⁷ kg/s and emplaced about 3 km³ of tephra within tens of hours. The unit comprises two layers of subequal thickness separated by a diffuse contact with the upper distinguished by being slightly coarser and less well sorted than the lower. The deposit’s coarser upper layer indicates either climactic conditions or a lesser degree of fragmentation during the latter half of the eruption. Strong winds distributed the deposit southwest of Misti, where it crops out over at least 800 km² and drapes the present site of Arequipa with up to 100 cm of tephra. The Sacarosa deposit is the first among the Cayma stage deposits, a distinctive group of felsic, biotite-bearing units, to be carefully described and its eruption characterized. Several Cayma stage deposits were emplaced by voluminous explosive eruptions similar to the Sacarosa eruption, representing a ~ 8.9–15.5 ky interval of powerful eruptions. Such an explosive eruption today would threaten Arequipa’s over 1,100,000 residents, many of whom live within the Sacarosa deposit’s distribution.