Photo by Icelandic photographer Örvar Atli Þorgeirsson. (and photo of the day on Science Daily - original: http://www.flickr.com/photos/orvaratli/4461539560/)

Currently in Iceland a 200-year dormant volcano is erupting.  The thick clouds of volcanic ash which began spewing into the air on or before April 13 are about 20,000 feet over the UK and Europe right now, grounding most (if not all) air traffic in those regions due to the fear that silicate particulate matter in the airborne ash will cause crashes.  And nobody is sure when the volcano will stop erupting – it may be months from now.  This volcano, named Eyjafjallajökull, is under a glacier.  Nearby, its bigger brother Mýrdalsjökull glacier (or Katla), which erupts every 60-80 years, may begin erupting in response to Eyjafjallajökull.

There are 6 categories of volcanoes, or openings in the earth’s crust where molten lava escapes: Shield volcanoes, Cinder volcanoes, Stratovolcanoes, Submarine volcanoes, Subglacial volcanoes, and the most powerful volcano of all, the Supervolcano.  These Icelandic volcanoes are the subglacial type, so after the lava melts the glacier the volcano that is formed has a flat (or table-top) shape.  Volcanoes essentially build themselves from products of their eruptions, unlike mountains which often occured when tectonic plates collided, pushing up the earth.  In 1980 Mt. St Helens in Washington state erupted, becoming one of the most studied and most discussed volcanic eruptions of the 20^th century.  Is the Icelandic volcano poised to become the Mt St Helens of the 21^st century?

Far-reaching effects of an erupting volcano (image from BBC news).

According to Science News, when an erupting volcano melts ice, floods known as jökulhlaups occur, and flooding from the Eyjafjallajökull eruption has already resulted in the evacuation of hundreds of Icelandic people.  The eruption also brought with it the sulfurous stench of rotten eggs.  So, an eruption of the larger brother volcano could wreak even greater flooding and devastation to the human population.  On the bright side, the volcanic ash in the atmosphere is expected to bring breathtakingly beautiful sunsets.

Various types of volcanoes (image from BBC news).

Volcanoes are as difficult to predict scientifically as earthquakes (see the Aliquot post on this, link below).  According to MSNBC’s science and technology page, there are three main places where volcanoes normally occur — along strike-slip faults, such as the one linked to Mount St. Helens' eruption in Washington state 30 years ago; along areas where plates overlap one another, such as in the Philippines and the Pacific Rim; and in areas like Iceland, which is affected by the movement of two geological plates in a so-called spreading system.  This Icelandic volcano’s eruption was first detected on March 20^th, with red clouds and 100-meter high fire fountains erupting from it.  The volcano then quieted a bit before erupting again (and with more severity) several days ago.  The fine ash is expected to affect water quality, as much drinking water is obtained from Icelandic glaciers.  The gases from the eruption also contain sulfur, which may act to reflect sunlight, with a slightly cooling effect in the region.  However, this eruption was relatively low on the volcanic explosivity index, which is measured from 1-8.

Map of the World's volcanoes (from USGS site below).

 FURTHER READING:

Tracking the Volcanic Ash Cloud:

http://thelede.blogs.nytimes.com/2010/04/16/tracking-the-volcanic-ash-cloud/?ref=europe

General science resources on volcanoes:

http://www.geology.sdsu.edu/how_volcanoes_work/

http://www.usgs.gov/science/science.php?type=feature&term=1209

http://www.volcano.si.edu/

 Aliquot post: Can we predict earthquakes accurately?

http://open.salon.com/blog/aliquot/2010/01/14/can_catastrophic_earthquakes_be_accurately_predicted