Luis E. Lara

The Unexpected Awakening of Chaitén Volcano, Chile

On 2 May 2008, a large eruption began unexpectedly at the inconspicuous Chaiten volcano in Chile’s southern volcanic zone. Ash columns abruptly jetted from the volcano into the stratosphere, followed by lava dome effusion and continuous low- altitude ash plumes [Lara, 2009]. Apocalyptic photographs of eruption plumes suffused with lightning were circulated globally. Effects of the eruption were extensive. Floods and lahars inundated the town of Chaiten, and its 4625 residents were evacuated. Widespread ashfall and drifting ash clouds closed regional airports and cancelled hundreds of domestic flights in Argentina and Chile and numerous international flights [Guffanti et al., 2008]. Ash heavily affected the aquaculture industry in the nearby Gulf of Corcovado, curtailed ecotourism, and closed regional nature preserves. To better prepare for future eruptions, the Chilean government has boosted support for monitoring and hazard mitigation at Chaiten and at 42 other highly hazardous, active volcanoes in Chile. The Chaiten eruption discharged rhyolite magma, a high-silica composition associated with extremes of eruptive behavior ranging from gentle lava effusion to violent, gas-driven explosions. As the first major rhyolitic eruption since that of Alaska’s Katmai-Novarupta in 1912, it permits observations that are benchmarks for future such events. It also reignites the debate on what processes rekindle long-dormant volcanoes, justifies efforts to mitigate rare but significant hazards through ground-based monitoring, and confi rms the value of timely satellite observations.

The role of dyking and fault control in the rapid onset of eruption at Chaiten volcano, Chile

Rhyolite is the most viscous of liquid magmas, so it was surprising that on 2u2009May 2008 at Chaitén Volcano, located in Chile’s southern Andean volcanic zone, rhyolitic magma migrated from more than 5u2009km depth in less than 4u2009hours (ref.u20091) and erupted explosively with only two days of detected precursory seismic activity. The last major rhyolite eruption before that at Chaitén was the largest volcanic eruption in the twentieth century, at Novarupta volcano, Alaska, in 1912. Because of the historically rare and explosive nature of rhyolite eruptions and because of the surprisingly short warning before the eruption of the Chaitén volcano, any information about the workings of the magmatic system at Chaitén, and rhyolitic systems in general, is important from both the scientific and hazard perspectives. Here we present surface deformation data related to the Chaitén eruption based on radar interferometry observations from the Japan Aerospace Exploration Agency (JAXA) DAICHI (ALOS) satellite. The data on this explosive rhyolite eruption indicate that the rapid ascent of rhyolite occurred through dyking and that melt segregation and magma storage were controlled by existing faults.

Interdisciplinary Studies of Eruption at Chaitén Volcano, Chile

High-silica rhyolite magma fuels Earths largest and most explosive eruptions. Recurrence intervals for such highly explosive eruptions are in the 100- to 100,000-year time range, and there have been few direct observations of such eruptions and their immediate impacts. Consequently, there was keen interest within the volcanology community when the first large eruption of high-silica rhyolite since that of Alaskas Novarupta volcano in 1912 began on 1 May 2008 at Chaiten volcano, southern Chile, a 3-kilometer-diameter caldera volcano with a prehistoric record of rhyolite eruptions [Naranjo and Stern, 2004semi; Servicio Nacional de Geologia y Mineria (SERNAGEOMIN), 2008semi; Carn et al., 2009; Castro and Dingwell, 2009; Lara, 2009; Munoz et al., 2009]. Vigorous explosions occurred through 8 May 2008, after which explosive activity waned and a new lava dome was extruded.

Use of Remote Imagery to Analyse Changes in Morphology and Longitudinal Large Wood Distribution in the Blanco River After the 2008 Chaiten Volcanic Eruption, Southern Chile

Abstract The 2008 haitén volcanic eruption generated significant changes in the channel morphology and large wood () abundance along the fluvial corridor of the lanco iver, southern hile. Comparisons of remote sensing images from the pre‐eruption (year 2005) and post‐eruption (years 2009 and 2012) conditions showed that in a 10.2 km long study segment the lanco iver widened 3.5 times from 2005 to 2009, and that the maximum enlargement was nine times the original width. Changes in channel width were lower between the years 2012 and 2009. The sinuosity and braiding indexes also changed between 2005 and 2009. After the eruption the channel sinuosity was higher and specific river reaches developed a braided pattern, but by 2012 the channel was recovering pre‐eruption characteristics. Huge quantities of were introduced to the study segment; individual per km of channel length were 1.6 and 74.3 in 2005 and 2009, respectively, and more than 30 log jams km−1 were observed in the year 2009. Between 2009 and 2012 the quantity of was very similar. Statistically significant relationships were found between the number of log jams and channel sinuosity and between the number of pieces of large wood with sinuosity and channel width. Wood was highly dynamic between 2009 and 2012: 78% of individual pieces and 48% of log jams identified in the 2009 image had moved by 2012. Finally the supervised classification of imagery associated with ArcMap tools was tested to identify large wood.