Iceland suffers from eruptions on average every 3 to 7 years. And in between we tend to look at other volcanoes with interest. And as time goes by we forget that Iceland at any time can have larger and faster eruptions than pretty much any other spot on earth.
During this phase of volcanic unrest we got a lesson about the breakneck pace that Iceland can put in during a period of volcanic unrest. At other volcanoes we can at a sedate pace follow volcanic intrusions and magma movement counted in anything from 100 meters per day, to a kilometre, or so.
But, once more, we are talking about Iceland. And today we got that reminder as Iceland decided that 5 kilometres in about 4 hours is a good pace for magma to ascend. That is by all means a new world record.
This is also an intrusion that will give scientific data for the next few years, even if there will not be an eruption. The reason for this is that we have never seen a large powerful intrusion at a Mid Oceanic Ridge at such a well instrumented place. We already have accumulated more data today, than at all other places and intrusions put together at a Mid Oceanic Ridge.
We now know that the initial swarm rapidly transformed from tectonic earthquakes, via volcano-tectonic, to earthquakes consistent with moving magma in a surprisingly short timeframe. As such this is turning into a potential eruption, or a state of volcanic unrest.
This does not mean that it is certain that an eruption will occur, just that the conditions are there for an eruption, if the seismic crisis continues for a length of time. According to previous knowledge an eruption would still be days to weeks away, even for Iceland. But, today we learned that there is indeed a higher gear on occasion for Iceland to put in.
This means that we must shorten the timespan from the start of the intrusion to a possible eruption considerably, if it happens. The normal timespan is 2 days up to weeks, months, or even years. In this case it is though more likely that it would continue at speed.
As such an eruption could be just hours to days away. That being said. If the current unrest stops in the next few hours there will be no eruption, at least for now. In that case we would end up with a Herðubreið situation with continuous small swarms, that ever so slowly moves magma towards the surface at the weakest point.
My personal musings
Let me state that it is the Icelandic Met Office that will make the call, and then it is up to the police and the Almannavarnadeild ríkislögreglustjóra to communicate and enforce it. They are the authorities in charge. I repeat, those are the ones to declare officially what is happening.
That being said, it is time to write what I think is going to happen. Currently the intrusion may end without an eruption. But, at the intensity and force of the current seismic unrest it is likely that an eruption will occur if the seismic crisis is prolonged.
If the earthquake swarm continues at this level an eruption could occur at any time from 8 hours to 72 hours from now. But, remember the IF here.
If an eruption would occur it would almost certainly not be explosive, at worst a VEI-1 to VEI-2. Instead it would be effusive with a fissure opening that could be anything from 500 meters to several kilometres in length.
Lava fountains would be between 100 to 700 metres in height, but fairly rapidly the fissure would shorten to one or a few main craters. At the same time, the eruptive rate would diminish to something between 50 to 500 cubic metres per second.
Eruptions in this area are known to last for quite some time, so an eruption could cause problems for the road leading from the airport and nearby residents for a prolonged time.
If I was forced to put numbers to a likelihood for an eruption I would say that it is currently below 50 percent, but that number is increasing by the hour. If the hubbub is still going at this rate in the morning I would give a higher number.
We will be following this event closely if it continues, and we hope to publish new seismic plots tomorrow as IMO divulge new data.
Happy volcano watching unto all!