As some has noted there has been quite a bit of activity in the last week at a volcanic feature that we have chosen to call Greip located north of Grimsvötn. We have previously written quite a bit about this feature and even gone so far as to state that it might be in a pre-volcanic state.
To recapitulate briefly what we know so far about Greip we first have to look at if there is something looking like a volcano on top of the point of interest, and we know that there is no edifice at the location. So, it has not erupted yet.
That being said, it was associated with the Holuhraun event in as much that the propagating dyke turned sharply to the north as it approached the northwest quadrant of Greip. At the least this means that the systematic pressure was to great for the dyke to proceed in that direction, some do though believe that Greip might have aided in the magma supply chain for the eruption.
Why do we think it is a proto volcano? This might be the simplest question to answer. Greip has since 2012 suffered from deep earthquakes indicating magmatic ascent into the system from depth. This activity has been incredibly persistent and narrowly defined into a clear deep feeder tube.
From 2012 onwards these earthquakes have slowly increased in numbers, and also moved on upwards from depths of around 35 kilometres to the current earthquakes between 20 and 12 kilometres. At the same time the general size of the earthquakes has increased about 20 percent, this might though be due to the magma pushing apart less hot and more brittle material causing more defined earthquakes.
In my last article I wrote that the magma slowly intruding under Greip had started to manifest itself as minor trackable movements in the GPS-trajectories, something that continued ever so slowly and minutely until last week.
A brief Bárðarbunga digression
During Holuhraun II eruption in 2014 we found that Bárðarbunga was not a triple-junction volcano as previously believed, instead it turned out that it is what might be the only meta-stable quad-junction volcano in existence.
From Langjökull running towards east via Hofsjökull and Vonarskarð you have the Mid Icelandic Belt, a volcanic rift zone that enters into Bárðarbunga from the west, Bárðarbunga itself is located on the western side of the East Volcanic Zone that is running in an SSW to NNE angle through Vatnajökull. This made Bárðarbunga into a triple-junction volcano.
But, as the Holuhraun II event started in 2014 we saw a clear path going towards east deeper into the East Volcanic Zone. We also know that this feature has been active at least once before, during Holuhraun I eruption in 1797 (this eruption was previously attributed to Askja).
Quad-junctions are inherently unstable and normally collapse into 2 different triple-junctions, this has not yet happened, so for the time being Bárðarbunga is a meta-stable quad-junction. The collapse will probably be caused by the Mid Icelandic Belt becoming defunct in the next 100 000 years or so.
What on earth did this now have to do with poor young orphaned Greip? Well, it makes it a triple-junction on the wrong end of Bárðarbunga since it is also sitting on what probably is the northern tip of the Grimsvötn Fissure Swarm. In other words, Greip has some violent parents.
The Week of the Living Greip
So, what then is the reason that we once more venture out into yet another article about a volcanic feature in Iceland that is not erupting when there are so many interesting volcanoes around the planet?
Well, as it turns out I have spent a few weeks reading up on and writing on an article about Monty Pythons favourite volcano, Kilimanjaro. In other words, not even I found Greip that interesting at the moment.
And like for all neglected puppies and babies throughout history there are two golden rules. One, if they are quiet you should assume that they are up to something bad. And, when you least expect it, they will manifest something really bad if you neglect them.
Puppies will chew up your handmade Italian shoes, and babies will inevitably find a crayon and redo your living-room walls into the Sistine Chapel. Volcanoes on the other hand will intrude glorious amounts of magma if you do not give them enough attention.
All alone under the ice Greip has suffered from six separate intrusive events in the last week. One can see them as smatterings of deep earthquakes ranging between 22- and 12-kilometres depth, but what is not seen is the extended periods of tremor that is accompanying those earthquakes.
The longest of those tremor periods lasted for slightly less than 4 hours, indicating that during the time frame there was freely flowing volcanic fluids. And at that depth it is not geothermal waters.
All of the earthquakes have been clearly defined inside the area that we have named Greip, so we know that it is not caused by any outside influence.
Greip and the GPS
Last time I wrote about Greip I explained how hard it was to separate Greip related signals from the other volcanoes in the area, but that it was possible and that there indeed had been inflation at depth.
This time around there is no need for careful data-analysis to see how Greip is affecting the general area, not when it is kicking stations about like it was playing football (not the American soft-rugby version).
GFUM (Grimsvötn) has been kicked 20mm south and 35mm up during the week. KISA (Bárðarbunga) moved slightly to the North-East and Up. The other nearby stations have also been moved around a bit while going up.
The sharp up-component will probably be temporary as the fissure swarm that Greip is situated on adjusts, so the trend should go down a bit, or at least slow down.
Greip and the future
Seeing a young volcano prior to its first eruption is in many ways a dream to research, because we have never seen how a volcano works as it is born. All we have are theories, and now finally we get to match them against real world instrumental data.
There is obviously quite a large risk that in the end Greip will fizzle out and never erupt, but it is allowed to hope for good things to come.
Currently there are four possible futures as I see it, five if you count the fizzle out possibility (but let us stay positive).
The first possibility is that as magma intrude, we will start to see more intense swarms as it gradually moves upwards due to heat-buoyancy, and that in a few years or decades our new little baby volcano will be born, wrinkled face and all.
If since it has done 23 kilometres in 7 years, I would say that it could erupt in about 5 years’ time at the going rate.
The second possibility is that Greip was helping out feeding the Holuhraun eruption. That means that it is quite possible that it might push magma northwards through the dyke towards Holuhraun, and that it will erupt there.
In my opinion this is not that likely since there is no remaining strain to rip apart a dyke in that direction.
The third option is that the magma will enter into the part of the dyke that is going between Greip and Bárðarbunga. This is not entirely impossible since Bárðarbunga is still under fairly low-pressure after the eruption in 2014.
Having hot deep gas-rich magma pushed backwards up through the wazoo of Bárðarbunga would probably become interesting. It would likely cause a fairly substantial caldera-eruption.
So far nothing seems to indicate that this is happening. There are no earthquakes in that part of the dyke, and Bárðarbunga is about as demure as it can be with its occasional Mw3s.
The fourth option is that the magma starts to move at depth along the Grimsvötn Fissure Swarm towards south feeding into the northern magma chamber of Grimsvötn. As of now we have not seen any substantial number of earthquakes indicating a rapid increase in magma influx into this volcano, so for now we can count this one out.
That being said, if magma started to move towards Grimsvötn we would rapidly see an eruption.
Whichever of the options that will manifest itself I am certain that we will start to see more vigorous and shallow earthquake swarms in anything from hours to a few months.