Mike Ross (@eruptionchaser) August 24, 2014 at 21:40
Carl, a masterly summary. A couple of points:

“The most surprising sign though is that this rifting fissure is not following a single fissure swarm. This is totally unsuspected behavior that nobody has even guessed at in their most feverish fantasies. The initial intrusion charged straight out of the Bárðarbunga fissure swam, passed barren land in between fissure swarms and connected with the Grimsvötn northern fissure swarm, followed that downstream and then once again changed trajectory and entered the fissure swarm of Askja.”

I think we have to reevaluate entirely what we *mean* by ‘fissure swarm’. In the past we have spoken glibly of such-and-such an eruption being an eruption on THIS particular fissure swarm, and therefore being an eruption of, or associated with, THAT central volcano. I don’t think that’s a valid bill of sale any more.

“This means that potentially the intrusion might be feeding on the 3 largest Icelandic volcanoes if the fissure evolves a bit more. If this actually happens all bets are off and we would be most likely talking about a rifting fissure eruption with explosive components.”

Likewise, I think we have to reevaluate what we mean by ‘central volcano’. I tend to suspect central volcanoes aren’t especially strongly related to rifting fissure events. I think ‘central volcanoes’ are what happens when the system is NOT in rifting fissure mode.

A more useful question is WHY central volcanoes exist in the Iceland fissure swarms, and WHY they exist WHERE they exist. I know this is being looked at now – George Walker has a model to explain this, Erik Klemetti told me. I haven’t looked in to this myself yet.