The Chaitén rhyolite lava dome: Eruption sequence, lava dome volumes, rapid effusion rates and source of the rhyolite magma

Abstract

ABSTRACT. We use geologic field mapping and sampling, photogrammetric analysis of oblique aerial photographs, and digital elevation models to document the 2008-2009 eruptive sequence at Chaitén Volcano and to estimate volumes and effusion rates for the lava dome. We also present geochemical and petrologic data that contribute to understanding the source of the rhyolite and its unusually rapid effusion rates. The eruption consisted of five major phases: The lava was erupted at relatively high temperature and is remarkably similar in composition and petrography to Chaitén's pre-historic rhyolite. The rhyolite's normative composition plots close to that of low pressure (100-200 MPa) minimum melts in the granite system, consistent with estimates of approximately 5 to 10 km source depths based on phase equilibria and geodetic studies. Calcic plagioclase, magnesian orthopyroxene and aluminous amphibole among the sparse phenocrysts suggest derivation of the rhyolite by melt extraction from a more mafic magmatic mush. High temperature and relatively low viscosity enabled rapid magma ascent and high effusion rates during the dome-forming phases of the 2008-2009 eruption.

Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

“…Such structures are often evident and have been studied in viscous intermediate lava flows (e.g. Cerro Chao, ChileFink 1980b;de Silva et al 1994; Puy de Cliergue, France- Latutrie et al 2017;San Pietro, Sardinia-Cioni and Funedda 2005;Santiaguito, Guatemala-Harris et al 2002, and other rhyolitic lava flows worldwide (Fink 1980a(Fink , b 1983Manley and Fink 1987;Carn et al 2009;Lara 2009;Bernstein et al 2013;Pallister et al 2013;Tuffen et al 2013;Magnall et al 2017).…”

“…Since 2008, real-time observations of active rhyolitic flow and dome emplacement at the Chilean volcanoes of Chaitén (Carn et al 2009;Lara 2009;Bernstein et al 2013;Pallister et al 2013) and Puyehue-Cordón Caulle Schipper et al 2013;Tuffen et al 2013;Bertin et al 2015;Farquharson et al 2015;Magnall et al 2017) have further developed our knowledge of rhyolitic lava emplacement. The Cordón Caulle eruption is an example of a flow that moved away from the vent, while Chaitén was a domeforming eruption.…”

“…The Cordón Caulle eruption is an example of a flow that moved away from the vent, while Chaitén was a domeforming eruption. Observations of the 2008 Chaitén eruption and associated composite rhyolite dome highlight simultaneous explosive and effusive activity, exogenous and endogenous growth phases and complex lava lobe and spine formation (Carn et al 2009;Lara 2009;Bernstein et al 2013;Pallister et al 2013). These resulted from multiple flow paths (flow directions of areas of active dome growth) within the lava dome, and different extrusion rates (Carn et al 2009;Lara 2009;Bernstein et al 2013;Pallister et al 2013).…”

“…Observations of the 2008 Chaitén eruption and associated composite rhyolite dome highlight simultaneous explosive and effusive activity, exogenous and endogenous growth phases and complex lava lobe and spine formation (Carn et al 2009;Lara 2009;Bernstein et al 2013;Pallister et al 2013). These resulted from multiple flow paths (flow directions of areas of active dome growth) within the lava dome, and different extrusion rates (Carn et al 2009;Lara 2009;Bernstein et al 2013;Pallister et al 2013). Morphological observations of the 2011-2012 Cordón Caulle eruption highlight the role of thermal insulation by a surface crust in prolonging flow-horizontal transport, channelled flow, surface crust formation, development of breakout lobes and flow frontal stalling Schipper et al 2013;Tuffen et al 2013;Bertin et al 2015;Magnall et al 2017).…”

Acute sedimentation response to rainfall following the explosive phase of the 2008–2009 eruption of Chaitén volcano, Chile

“…Eruption-generated mass flows and tephra fall can remove, bury, or damage vegetation (e.g., Swanson and Major 2005;Swanson et al 2013), mantle broad areas of terrain with tephra sufficiently fine to decrease soil infiltration capacity (e.g., Leavesley et al 1989;Ikeya et al 1996;Yamakoshi et al 2005), and load rivers with large quantities of volcaniclastic sediment (e.g., Newhall and Punongbayan 1996;Miyabuchi 1999;Major et al 2000;Pallister et al 2013b). As a result, volcanically disturbed drainage basins are subject to altered runoff and streamflow (e.g., Leavesley et al 1989;Yamakoshi and Suwa 2000;Major and Mark 2006) and to exceptional, and sometimes prolonged, erosion and sediment transport (e.g., Waldron 1967;Chinen, 1986;Thouret et al 1998;Lavigne et al 2000;Major et al 2000;Hayes et al 2002;Major 2004;Gran et al 2011;Pierson et al 2011).…”