Bristol Island. NASA It appears people got kind of nervous after my Mount St. Helens earthquake swarm post. Well, again, nothing with which to be concerned. Posts might be sparse for the next few days as I'll be getting ready to head to Oregon starting this weekend for labwork and fieldwork. More on that next week! Some updates from the volcano world: AlaskaCleveland, in the Aleutian Islands, has been on Orange/Elevated alert status since late last week after a series of explosions, including one early today. However, details about the activity are sparse as there is no real monitoring equipment at Cleveland beyond a webicorder (that records earthquakes and tremor) that indeed shows that the volcano is restless. Even the weather hasn't cooperated as clouds have obscured any satellite views of the volcano. Most of the information about these explosions have come from the seismic information of the webicorder and infrasound that picks up low frequency noises associated with explosions. Sometimes it can be a real challenge to confirm an eruption occurred in these remote locations and it is this circumstantial evidence like infrasound and earthquakes that are our best clues. Most of the threat from eruptions at Cleveland influence air travel, as only nine people live within 100 kilometers of the volcano. South Sandwich Islands In an even more remote location, the NASA Earth Observatory posted an image of
Sourabaya on Bristol Island in the South Atlantic Ocean. This appears to be the first eruption (that anyone has noticed) on Bristol Island since 1956, when the volcano produced a VEI 3 eruption that created a small cinder cone on the flanks of the main edifice. This current activity appears to be more of the lake-lava flow variety.
Bristol Island lies within the South Sandwich Islands, which has number of active volcanoes, including Curry that erupted in 2012. No one lives within 100 kilometers of Bristol Island, so it is safe to say that there isn't much threat posed by the eruption. Noticing eruptions like this, thanks to satellite eyes watching, are a big reason that is seems that the planet is more volcanically active. It isn't, but we just know a lot more about eruptions as they happen even at really remote volcanoes like Bristol Island and Cleveland.
Chile Yesterday saw an uptick in the activity at Chile's Nevados de Chillán, with some vigorous albeit low-level ash-rich explosions from the active vent. The plume reached ~1.7 kilometers (5,500 feet) over the volcano. The ash emissions quickly waned with the seismicity, so the SERNAGEOMIN has kept Nevados de Chillán at Yellow Alert status. You can check out some video taken of the eruption by nearby residents. Today, only a small steam plume is visible on the Nevados de Chillán webcam. New Zealand The unrest I mentioned last week at Ruapehu in New Zealand took an unexpected turn over the weekend as the crater lake continued to heat. Tourist flights of the volcano noticed vigorous steaming and bubbling at the lake's surface over the weekend and the lake water reached 44ºC. However, a GNS Science flight over the crater lake showed nothing particularly alarming. Even with all this, the alert status at Ruapehu has been kept at Green/Level 1. UPDATE 8 pm EDT 5/10/16: After visiting Ruapehu today, GNS Science has raised the alert status to 2 and aviation alert to yellow. This is due to the high lake temperatures (now 45ºC), continued seismicity and increasing emissions of carbon dioxide and sulfur dioxide. Looks like Ruapehu needs to be closely watched --- which you can do on the GeoNet webcams. White Island remains at a more elevated alert status (Yellow), although the Volcanic Alert Level was lowered from 2 to 1 after decreases in gas emissions and earthquakes. GNS Science posted an excellent article on the April 27 eruption that covers how you can be sure an eruption occurred when no one is there to see it and answers some of the questions people had about the eruption.
