Iceland has been undergoing a long term powerful eruption occurring at Bardarbunga Volcano.
Here is video of the eruption from September, when the lava flow began in earnest:
Here is video of the Eruption from last month in November 2014, still going strong:
The Holuhraun eruption has produced some VERY impressive lava flows, and also has caused thousands of noteworthy earthquakes in the 4.0M – upper 5.0M range.
The earthquakes have been occurring along the new volcanic fissure, as well as areas around the deep lava chamber located below the Bardarbunga volcanic complex.
Here is a plot of the earthquakes from September to December 2014.
This animation below clearly shows the progression of the earthquakes along the fissure zone, and also shows the movement near the volcanic chambers directly:
On top of the above confirmed lava flow activity, a new report from volcanologists in Iceland states that the CALDERA IS COLLAPSING at Bardarbunga.
“19 December 2014 12:00 – from the Scientific Advisory Board
Yesterday, 18 December, scientists flew over Bárðarbunga. The data collected in the flight show that the subsidence of the caldera continues with similar rate as before and amounts to about 56 m in total from the onset of the unrest. The total volume of the caldera subsidence is estimated to be about 1.7 km³. Minutes from the meeting of the Scientific Advisory Board (pdf 0.4 Mb)
The reports say that an area the size of 2km at Bardarbunga has “subsided” (collapsed) by 56m / 183 feet since the eruption began. The caldera will reach a critical mass, once the weight above exceeds the support of the chamber below, then entire area will subside / collapse rapidly.
This is a huge area to collapse. As we’ve seen in OTHER collapses, when the surface collapses into the emptying caldera, a large eruption ensues.
See the 2011 collapse of Pu’u’ O’o’ caldera in Hawaii as an example of what can occur when the chamber below the volcano gives way to the weight above.
Keep in mind, Pu’u O’o is MUCH smaller in size compared to Bardarbunga in Iceland. Hawaii’s volcano being just a few hundred meters across, whereas Bardarbunga is MILES across – literally 200 km (120 mi) long and 25 km(16 mi) wide.
2km of the 200km region is subsiding.