This week's Vulcan's View is a little focused than most - so if you're looking for news of eruptions outside of Chile, be sure to read the complete Smithsonian/USGS Global Volcanism Program Weekly Volcanic Activity Report. Lots of news there, including Cleveland in Alaska, that was recently lowered to Yellow Alert from Orange and the ever-popular El Hierro, where the eruptive activity south of the island has resumed with gusto. On to Chile!
This excellent Terra image taken on October 31 and shows three volcanoes in different states of activity. In the far north (top) of the image, the healthy plume from Puyehue-Cordón Caulle is clearly visible. The ash from the eruption - clearly grey/white - is swirling to the southeast and southwest of the volcano, which is the opposite direction of the image from last week. Some of the ash has made it all the way to Porto Alegre, Brasil where they created a volcanic haze. Midway down the image, you can see the new dome from Chaitén. No plume is visible, although occasionally steam plumes with minor ash and glowing at night that can be seen coming from the dome complex. You can see the that the drainages surrounding Chaitén are still light colored with the volcanic debris from the eruption that started in 2008 but looks to be winding down. The SERNAGEOMIN has Chaiten at alert Level 2 Green, saying the volcano is stable and there is no immediate risk of volcanic activity. Finally, in the south (bottom) is Cerro Hudson, which recently sprang back to life after almost 2 decades of relative quiet. In the top image, you can see the dark smudge on the white snows - that is all the ash from the small "throat-clearing" eruption from this week. Note how different the ash color is as compared to Puyehue-Cordón Caulle. If we take a closer look at Hudson in the ALI EO-1 image (below) taken on November 1, 2011, the ash is clearly visible spreading eastward from the three vents on the volcano, but real plume is visible in the image. SERNAGEOMIN/OVDAS has lowered the alert status at Hudson to Level 4 Yellow from Red, suggesting at an eruption is not likely in days to hours, but possible days to weeks. The eruptive activity has ceased but the seismicity continues, suggesting magma moving under the volcano. Additionally, juvenile (new magma) material was found in the ash from the small eruption this week, supporting the idea that this is more than just steam-driven explosions at Hudson.
OVDAS/SERNAGEOMIN will keep a close eye on on Hudson during the following weeks - and they have installed a webcam to help with watching the volcano's activity (NOTE: the webcam looks to be down right now). All in all, it is a busy time for volcanoes in the southern parts of Chile.