Christina Neal

... of the third explosive burst and some or all of the ensuing hours of continuous ash emission, including ... fieldwork in June and August 2009 it was evident that Kasatochi was still emitting volcanic gas. Odors of both SO2 and H2S were persistent on the lee side of the island, both ...

Based on preliminary analysis of monitoring and other data from the 2009 eruption, the last two eruptions of Redoubt Volcano (1989-90 and 2009) are similar in some respects, and yet remarkably different in others. Both eruptions consisted of multiple explosive events from a vent bored through glacial ice in a 2-km-wide summit amphitheater. Individual explosive events during 2009 are best described as Vulcanian and/or phreatomagmatic, whereas many individual events during the 1989-90 eruption originated by dome collapse. The 2009 eruption was preceded by about 175 days of increased fumarolic activity, gas emissions, and heat flux at the summit. Although less well-monitored, the 1989-90 eruption was preceded by only about 23 days of noted unrest. Deep (25-30 km), long-period (DLP) earthquakes occurred several months prior to eruption in 2009; no DLPs were detected in 1989 prior to the eruption, but we will note that seismic acquisition software has since improved. The initial 2009 exp...

Mt. Cleveland is one of more than 40 active volcanoes in Alaska that is monitored by the Alaska Volcano Observatory (AVO). It is located on the western half of Chuginadak, a remote and uninhabited island in the east central Aleutians that lies 1526 km southwest of Anchorage. The closest inhabited community, Nikolski, is 75 km to the east on Umnak

The 10-km-wide caldera of the historically active Aniakchak volcano, Alaska, subsides ˜13 mm/yr, based on data from 19 European Remote Sensing Satellite (ERS-1 and ERS-2) interferometric synthetic aperture radar (InSAR) images from 1992 through 2002. The pattern of subsidence does not reflect the distribution of pyroclastic deposits from the last eruption in 1931 and therefore is not related to compaction

ABSTRACT [1] We report CO2, SO2, and H2S emission rates and C/S ratios during the five months leading up to the 2009 eruption of Redoubt Volcano, Alaska. CO2emission rates up to 9018 t/d and C/S ratios ≥30 measured in the months prior to the eruption were critical for fully informed forecasting efforts. Observations of ice-melt rates, meltwater discharge, and water chemistry suggest that surface waters represented drainage from surficial, perched reservoirs of condensed magmatic steam and glacial meltwater. These fluids scrubbed only a few hundred tonnes/day of SO2, not the >2100 t/d SO2expected from degassing of magma in the mid- to upper crust (3–6.5 km), where petrologic analysis shows the final magmatic equilibration occurred. All data are consistent with upflow of a CO2-rich magmatic gas for at least 5 months prior to eruption, and minimal scrubbing of SO2by near-surface groundwater. The high C/S ratios observed could reflect bulk degassing of mid-crustal magma followed by nearly complete loss of SO2in a deep magmatic-hydrothermal system. Alternatively, high C/S ratios could be attributed to decompressional degassing of low silica andesitic magma that intruded into the mid-crust in the 5 months prior to eruption, thereby mobilizing the pre-existing high silica andesite magma or mush in this region. The latter scenario is supported by several lines of evidence, including deep long-period earthquakes (−28 to −32 km) prior to and during the eruption, and far-field deformation following the onset of eruptive activity.