Volcanoes rarely follow human timescale and human planning. This time it is Þorbjörn that decided to ruin things just after Albert had published a truly nice read about Santa Maria.
Þorbjörn better do as told below, otherwise Albert will have words with the volcano in question for ruining his article scheduling.
In the last 4 years the Reykjanes Fires have kept us amused, and as Þorbjörn is getting closer and closer to erupting I thought we should begin with a short recap.
Before Fagradalsfjall erupted 3 times it all began with Þorbjörn suffering from a powerful earthquake swarm, and an intense inflationary period where it uplifted 80mm.
The magmatic intrusion stopped that time at around the 5km mark, and since then the magma has been sitting there in situ, waiting for better times, and instead we got the 3 Fagradalsfjall eruptions as the pre-show amusement.
The first of those was a pretty tourist eruption that continued for quite some time, the second one threatened to overrun the road, a couple of houses, and burial site. Thankfully none of this happened.
And the third one was fairly unremarkable as Icelandic eruptions go, but the tourists that got there in time got their money’s worth at least.
Last few weeks
During the last couple of weeks Earthquake activity resumed over at Þorbjörn, and that in turn developed into a proper earthquake swarm with magma-tectonic earthquakes. But, to muddle the waters a swarm also started toward the tip of the Reykjanes peninsula, but those earthquakes steadfastly remained tectonic in nature.
About a week ago rapid inflation set in as the intruding magma pushed up the area above, and this inflation can be seen well across the entire Reykjanes Peninsula. By now the inflation has reached 60mm, plus the 80mm that was intruded in the last seismic crisis, so in total the area has inflated 140mm.
The GPS gives this as 100mm in total, but that is due to subsidence caused by Fagradal, and due to the area naturally subsiding over time. But the area directly above the magma is 140mm higher than what is should have been compared to other non-affected areas, if you catch my rift (drift).
If we track the earthquakes that are larger than 2.5Mw we end up with them peaking at about 2.1km, those that are smaller are not well defined enough to be able to pinpoint depth enough to really be trustworthy, so let’s stick with the 2.5Mw as a good marker for what is a minimally trustworthy earthquake (no earthquakes are ever trustworthy…), and only if it has a 99 percent marker and is corrected by hand.
2.1km is at, or very near the border of where a volcano will become a runaway train in regards of erupting, due to buoyancy the magma will continue upwards if left alone, and 400 meters higher and it will start to nucleate out volatiles, and at that point nothing can stop an eruption from happening.
Regardless of this, the earthquake swarm is continuing due to magma building up the pressure, so it is not even left alone to its own devices.
At 00.04 Sunday morning the mountain suffered from a sudden strain increase at the same time as there was an earthquake doublet.
If it had been a drunkard outside a pub, this was the first dry heave before that type of eruption. And if we would state it with another physical human process, Þorbjörn had a contraction but the birthing canal was not dilated enough.
During that time there was a tremor episode also indicating that it was one of those “close, but no fish” situations.
But when contractions have started there will be a baby in the end. Yes, it may be a false contraction, and the baby will shoot out a few days later, but it is sort of assured that soon you will need a mountain of diapers at hand.
Now it depends on how fast the earthquakes breaks open the volcanic birthing canal, I do not think it will take a long time.
I would say that it is pretty close, at anything from a few hours, up to a couple of weeks. The Icelandic Met Office has it as within a year, but that statement came prior to the last 24 hours.
I would definitely take a bit of time to go out and grab some popcorn and find some nice webcams of Grindavik.
Volcanoes that have a fissure line like Þorbjörn are tricky to say where they will erupt specifically, but a good guess would be 3-5km from the town centre of Grindavik towards the Þorbjörn mountain itself.
This is a tricky spot since magma pouring out there relatively quickly would get to the town. There is also the potential that the dyke will propagate further south near the surface and pop up in someone’s basement.
I seriously hope that the last thing will not happen since it would be dangerous.
Þorbjörn is close to erupting now, and if it happens it will most likely impact the lives of the citizens of Grindavik. I do know that they are well informed and are ready to go within minutes of notice, and if it pops up at around where the earthquakes are heading, there will be time to evacuate.
I am not sure if the Icelandic authorities will try to save Grindavik by digging trenches and spray water on the advancing magma front like they did under Fagradal 2 and the Heimaey eruption respectively, but I would sort of assume that the Icelanders will have a go at it since they tend to fight their volcanoes.