An extract from an article on Volcano cafe. Its about the potential eruption at the caldera and the ring faults.
Since the appropriate Icelandic authorities have today publicly mentioned the possibility of a large, acidic and explosive eruption at Bardarbunga, we now feel free to inform you that this possibility has been discussed by the Dragons, behind closed doors, for well over a week. The key information comes from this official IMO graphic:
The first premise is that earthquakes do not occur in molten rock. Nor do they form a clearly visible ring shape such as the above except under one circumstance – they do so around a body of liquid, in this case magma. A conservative estimate places the size of this body of magma at 8 km diameter, height unknown but most likely on the order of 3 – 6 km, depth also unknown but relatively shallow. Using simple geometry, 4 x Pi x r3 / 3 yields a volume of ~250 cubic kilometres for a sphere, but for our flattened body something on the order of 125 – 140 cu km.
The link is here http://volcanocafe.wordpress.com/2014/09/03/bardarbunga-update-20140903/