Askja Is Stirring, But… (March 21, 1636 UTC)

Update, March 21, 2023, 9:36 a.m., Pacific: No news is good news. As far as I know, Askja’s big lake remains frozen.

Last Friday, the 17th, boffins held a meeting (Icelandic).

Here is the summary, in tweets:

Update, March 13, 2023, 12:05 p.m., Pacific: Ice has formed again on the crater lake, but…:

…She says it is no surprise that the surface of the lake is now frozen, but says it is exciting to watch what happens next.

“There is evidence that the geothermal heating has increased recently. We will see in the coming days whether it was a passing phase or whether it will continue. We will see whether this ice is allowed to remain in peace or not.”

She states that if the ice melts, scientists will get a better indication of what is happening at Lake Askja.


Original post:

It is more accessible in summer. (Image: Oleg Senkov/Shutterstock)

Those satellite images (Source) show the main news about this Icelandic caldera complex: one of its crater lakes has gotten warm enough to melt the ice covering it despite current winter conditions there.

And no one really is sure why.

That’s the only solid information I’ve been able to verify about this news since first hearing about it last month on Twitter.

At that point, the Icelandic Met Office website described the situation but saw no other precursors (my interpretation — BTW, that link should autotranslate the original Icelandic, but you might need to do that yourself after refreshing the page).

Then, in the past week, a well-known and, I think, reliable volcanologist has been telling the local media that he expects an eruption, but doesn’t know when it might occur (here is today’s story).

And he’s the only one saying this.

So, I’m curious, but it isn’t easy to get more information online.

This 2014 news story was interesting, but no Askja eruption followed.

In 2021, I did a post on it; no follow-up was needed because, again, things stayed quiet.

In this part of Iceland, you can stand on the North America-Eurasia tectonic plate boundary! (Image: Scoundrelgeo via Wikimedia, CC BY-SA 4.0)

So today I read that interview with the volcanologist linked earlier and then unsuccessfully looked for additional reliable information via Google, Twitter, and YouTube.

The lack of public comment by the various boffins I follow interests me more than the hysteria (all undocumented) on YouTube.

Scientists and other responsible people keep quiet and observe when something interesting is going on and they don’t yet understand it.

When it is clear to them, they LOVE to talk about it — witness all the pre-eruption excitement at Fagradalsfjall, for example — both times.

So let’s assume that something interesting is going on at Askja (here’s its Global Volcanism Program page).

It’s clear to Þorvaldur Þórðarson what’s going on, but other experts apparently aren’t yet sure.

As for us, let’s take a run out there to get acquainted with a volcano that’s worth our keeping an eye on it for a while.

“Accessible” has a different meaning in Iceland. From this video, it looks like Askja might be almost right on the plate boundary between North America and Eurasia — no wonder it’s complicated.

Last October, the folks at Volcano Cafe came up with an explanation for the crater lake warming that doesn’t require an impending magmatic eruption:

During the last year Askja has inflated with more than 40 centimetres locally inside the caldera. This has led many people to state that an eruption is close. I seriously doubt that it is the case due to what is missing in the picture.

It can be summed up in a single question. Where are the earthquakes? After all, Icelandic volcanoes are famously noisy prior to eruption with two glaring exceptions to the rule, Grimsvötn and Hekla. But they are very special exceptions caused by an open constant feeder mechanism from the mantle that is held open due to them frequently erupting and that they have a steady supply of fresh magma slowly entering the system.

Askja on the other hand is as far as known more episodic, with large intrusions happening, and after that follows diminishing eruptions of ever more stale magma due to lack of influx. Other such volcanoes are quite noisy prior to eruption.

There is also a lack of deep earthquakes and no clearcut deep feeder that is visible on the earthquake data from the MOHO up to the magma reservoir.

What has been detected is though a deep accumulation of magma below the crust trying to find its way upwards, this was especially evident in 2013 prior to the eruption at Holuhraun. This caused a broad and widespread movement upwards of the entire volcanic system of Askja.

Instead, we have a highly localized spot that is inflating quietly at a depth of 2.5 to 3 kilometres depth.

Let us now look at the caldera inside the caldera rim. We know that it has suffered from at least 3 major calderification events, ranging from a mid-sized VEI-5 up to a good sized VEI-6. These eruptions did not directly cause the formation of the caldera due to massive explosive eruptions, or technically it is calderas in plural.

Instead, the void created by profuse effusive eruptions caused the roof to crack and fall into the magma reservoir in the form of blocks of rock. Unlike Bardarbunga that is acting like a piston due to the depth of the magma reservoir, it is easier for Askja to just drop down piece by piece.

This has created a complete mess down to the shallow magma reservoir of crushed up rocks, and crushed rocks are fairly aseismic. It has also created a good ground for water to percolate down through.

We also know that there is a lot of ground water at Askja, we know this from the two caldera lakes inside the volcano. We also know that Askja is hydrothermally active.

So, let us now toy with the thought that water has slowly percolated down through the jumble of rocks until it came near the magma reservoir. Here the rocks are more stable and can create a non-permeable lid.

Under that local lid the water would happily expand as it converts into supercritical fluid and lift the lid upwards. Water that is not under the lid will just move upwards as ordinary geothermal water and heat up the area at the surface, something that we know has happened at the lake.

The lake used to freeze over, now not so much. So, we know there is an increase in hydrothermal water circulation.

This is how you get a mysterious quiet large uplift without any trace evidence of fresh magma intruding into the magma reservoir.

Potentially in the end we might end up with a Maar formation, and those can indeed be spectacular in their own right, but we will need quite a bit more inflation before that happens.”

Even a maar eruption at something the size of Askja would be awesome.

Well, let’s get some popcorn and wait for the next development!

This is also the Sunday Morning Volcano post, one day early. I’m still working on the Merapi chapter revision. Don’t laugh: the ones on Vesuvius and Etna took all of last summer and a sizable chunk of spring and fall, too!

I will never approach such a big project so lightly again — but I will probably take on more such projects. 😍


Meanwhile, among the weirder videos about Iceland this morning…

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