Simon A. Carn | Search USGS

USGS2013

Evaluation of Redoubt Volcano's sulfur dioxide emissions by the Ozone Monitoring Instrument

The 2009 eruption of Redoubt Volcano, Alaska, provided a rare opportunity to compare satellite measurements of sulfur dioxide (SO 2 ) by the Ozone Monitoring Instrument (OMI) with airborne SO 2 measurements by the Alaska Volcano Observatory (AVO). Herein we: (1) compare OMI and airborne SO 2 column density values for Redoubt's tropospheric plume, (2) calculate daily SO 2 masses from Mount Redoubt for the first three months of the eruption, (3) develop simple methods to convert daily measured SO 2 masses into emission rates to allow satellite data to be directly integrated with the airborne SO 2 emissions dataset, (4) calculate cumulative SO 2 emissions from the eruption, and (5) evaluate OMI as a monitoring tool for high-latitude degassing volcanoes. A linear correlation (R 2 ~ 0.75) is observed between OMI and airborne SO 2 column densities. OMI daily SO 2 masses for the sample period ranged from ~ 60.1 kt on 24 March to below detection limit, with an average daily SO 2 mass of ~ 6.7 kt. The highest SO 2 emissions were observed during the initial part of the explosive phase and the emissions exhibited an overall decreasing trend with time. OMI SO 2 emission rates were derived using three methods and compared to airborne measurements. This comparison yields a linear correlation (R 2 ~ 0.82) with OMI-derived emission rates consistently lower than airborne measurements. The comparison results suggest that OMI's detection limit for high latitude, springtime conditions varies from ~ 2000 to 4000 t/d. Cumulative SO 2 masses calculated from daily OMI data for the sample period are estimated to range from 542 to 615 kt, with approximately half of this SO 2 produced during the explosive phase of the eruption. These cumulative masses are similar in magnitude to those estimated for the 1989–90 Redoubt eruption. Strong correlations between daily OMI SO 2 mass and both tephra mass and acoustic energy during the explosive phase of the eruption suggest that OMI data may be used to infer relative eruption size and explosivity. Further, when used in conjunction with complementary datasets, OMI daily SO 2 masses may be used to help distinguish explosive from effusive activity and identify changes in lava extrusion rates. The results of this study suggest that OMI is a useful volcano monitoring tool to complement airborne measurements, capture explosive SO 2 emissions, and provide high temporal resolution SO 2 emissions data that can be used with interdisciplinary datasets to illuminate volcanic processes.

Alaska↗

USGS2012

The 2010 explosive eruption of Java's Merapi volcano—A ‘100-year’ event

Merapi volcano (Indonesia) is one of the most active and hazardous volcanoes in the world. It is known for frequent small to moderate eruptions, pyroclastic flows produced by lava dome collapse, and the large population settled on and around the flanks of the volcano that is at risk. Its usual behavior for the last decades abruptly changed in late October and early November 2010, when the volcano produced its largest and most explosive eruptions in more than a century, displacing at least a third of a million people, and claiming nearly 400 lives. Despite the challenges involved in forecasting this ‘hundred year eruption’, we show that the magnitude of precursory signals (seismicity, ground deformation, gas emissions) was proportional to the large size and intensity of the eruption. In addition and for the first time, near-real-time satellite radar imagery played an equal role with seismic, geodetic, and gas observations in monitoring eruptive activity during a major volcanic crisis. The Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) issued timely forecasts of the magnitude of the eruption phases, saving 10,000–20,000 lives. In addition to reporting on aspects of the crisis management, we report the first synthesis of scientific observations of the eruption. Our monitoring and petrologic data show that the 2010 eruption was fed by rapid ascent of magma from depths ranging from 5 to 30 km. Magma reached the surface with variable gas content resulting in alternating explosive and rapid effusive eruptions, and released a total of ~ 0.44 Tg of SO 2 . The eruptive behavior seems also related to the seismicity along a tectonic fault more than 40 km from the volcano, highlighting both the complex stress pattern of the Merapi region of Java and the role of magmatic pressurization in activating regional faults. We suggest a dynamic triggering of the main explosions on 3 and 4 November by the passing seismic waves generated by regional earthquakes on these days.

Merapi volcano↗