Tuesday, May 20, 2014

Antarctic Ice Melt Could Unleash Volcanoes

The news on the environment lately hasn't been very good. Climate change has reached a tipping point with over 400ppm carbon in the atmosphere (a tipping point scientists have said is the point at which man-made changes to the climate become irreversible). Ocean acidifcation is reaching epic proportions and wreaking havoc on the oceans ability to sustain life. And to top that all off, scientists now say that the ice sheets in Antarctica have 'reached the point of no return' and their gradual slide into the ocean will raise sea levels by up to 30 feet (10m) in the coming two centuries.

Oh, but they forgot about volcanoes!

As has been speculated in a much smaller environment, 'post-glacial rebound', the process where land raises (in some cases rapidly) due to the absence of ice, could result in more frequent volcanic eruptions. This has been theorized in places like Iceland, where 'seasonal' volcanism sometimes occurs (although, of course, not always). The theory goes something like this: If you have a large volcanic system that is covered by thick layers of ice, the weight of that ice presses down the volcano and surrounding crust, thus containing any surface volcanic activity.

We do  know that volcanoes can erupt under ice. Such eruptions can create devastating ash clouds such as the one emitted during the 2010 eruption of Eyjafjallajökull in Iceland, and others leave flat topped mountains called 'tuyas', which formed when volcanoes erupted under the ice, but never broke through to the surface. Tuyas are common volcanic mountains in Western Canada in volcanic complexes such as the Tuya Volcanic Field, and other systems.

But we're not talking about Tuyas, we're talking about large stratovolcanoes. Really big ones.

You wouldn't think of Antarctica as the first place to find active volcanoes, but you'd be wrong. In fact, we don't even know how many active volcanic systems exist in Antarctica, and which ones might be active far beneath the ice. Only recently has some technology been able to scan beneath the ice sheet, but these scans only reveal topography. Not heat, or chemical composition of the rock to tell us where certain spots might be. So the question of crustal rebound reaches a new level of uncertainty with Antarctica.

Antarctica does have at least one historically active volcano, and possibly several more. Mt Erebus is the most active in Antarctica with many historical eruptions documented since the 1970's, however other volcanoes have been spotted with fumerolic activity, and some are suspected to have had minor eruptions in historical time. What's occurring beneath the ice sheets however is anyone's guess. And in the next couple hundred of years, if crustal rebound truly does allow for easier magma flow to the surface, we'll probably find out if there are any more.

Monday, May 5, 2014

Mt St Helens Is Inflating Again

It appears that Mt St Helens is experiencing gradual re-inflation of its magma chamber, leading some to feel concern that the volcano will erupt again in the near future. St Helens last eruptive period ended in 2008 with a dome building event, which consisted of slow extrusion of a central lava dome, and occasional ash fall due to collapse of the dome. The current inflation period does not indicate an eruption is imminent, although it does significantly raise that possibility.

It is common for volcanoes to immediately begin 'recharging' after the end of eruptive activity. Other volcanoes that display this behavior are volcanoes such as Hawaii's Mauna Loa, or Kilauea, which experience frequent eruptions and deflation/inflation (DI) events. Mauna Loa began to inflate immediately after its 1983-84 eruption, stopped in 2009, and gradually resumed inflating in 2010. There are no current indications despite this inflation that an eruption of Mauna Loa is imminent, however it is a cause for vigilance.

St Helens erupted in May 1980 after bulging was detected on its north flank, followed by a massive collapse and associated eruption. It is one of the largest eruptions in recent US history, and is frequently used as a comparison benchmark for other volcanic eruptions. Monitoring of Cascade range volcanoes, and other US volcanoes was stepped up after the 1980 eruption, as the US finally realized the threat that monitored volcanoes can present. St Helens was monitored prior to its eruption, and warnings were issued that the volcano might erupt, but sadly some 57 people were killed and up to 250 homes were destroyed in the famous eruption.

USGS heavily monitors St Helens, as it is one of only several volcanoes on the West Coast with a recent history of eruption. In 1914-1917, California's Mt Lassen erupted, and Washington's Mount Rainier erupted in 1894.

Currently, all volcanoes on the West Coast of the US are 'green' meaning there are no warnings in place at the moment.

St Helens, Rainier, Shasta, and several other Cascade range volcanoes are considered a high risk for populations should they erupt. Rainier in particular is of major concern to scientists who warn that even without an eruption, it is at severe risk of collapse and associated hot mudslides known as 'lahars', which can cause major damage down well established canyons and drainage channels. There is an alert system in place, however it does not provide a lot of time to react should it go off.