In a recent article, I covered how Bárðarbunga's caldera has dropped down over 15 meters since this event began 2 1/2 weeks ago, an average of 60 centimeters per day. This collapse not only represents an elevated risk of eruption, but also makes any potential eruption more dangerous by providing an area for a quarter cubic kilometer of water to pool under the glacier.

Well, the collapse is apparently still ongoing. Today's fight measured an additional 2.8 meters of subsidence in the calera since Saturday (from 15.8 meters to 18.5 meters), or an average of around 90 centimeters per day.

The obvious question - does this mean that it's going to erupt - unfortunately gets the same answer as last time when the collapse was first discovered: We don't know. A caldera can collapse without an eruption. A collapse can also trigger an eruption, driving out out magma at tremendous rates and to huge heights. A collapse can be in slow steady increments. It can also drop hundreds of meters at once. Regardless of the possibilities, seeing this kind of activity in a caldera is not a good thing.

Especially not a caldera this big:

Compared to its dozens to hundreds of cubic kilometers (only a fraction of which would be expected to erupt), the current outflow onto Holuhraun is quite little, about 100 million cubic meters (0.1 cubic kilometers), covering 19 square kilometers. But how big, exactly, is what we're seeing as it stands?

We've already covered the unprecidented nature of the earthquake swarm. In terms lava, this is already one of the biggest lava eruptions in Iceland since the start of the 19th century, and its lava is much gasier than other well studied volcanoes such as Krafla. Of course, one has to put the "19th century" cutoff because of that "little" volcano in the late 1700s known as Laki. How does this compare to his last major eruption? Here's a map where someone overlaid the area of Holuhraun's flow over that of Laki's:

Holuhraun's (now 19) square kilomters of flow is dwarfed by Laki's 565. However, Laki also erupted for 8 months, versus about 10 days for Holuhraun thusfar. The rate of land coverage is fairly similar. However, it should be noted that Laki emitted 10 cubic kilometers of lava, which is about three times the average volumetric flow rate of the current Holuhraun eruption.

Does that mean both of these comparisons will hold with time? Of course not. While there's a general consensus that the current event will go on "for a long time", we have no clue whether that will be weeks, months, or years. Likewise, it's almost inevitable that the flow rate will change with time, either accelerating (say, an eruption of the caldera) or decelerating (say, cessation of flow without an uncontrollable increase in pressure). The same occurred with Laki - at times the flow rate was nearly 5000 cubic meters per second, while at others, just a trickle.

In short? We have no clue what's going to happen.

So where is this lava going? As it stands, primarily northeast at about 100 meters per hour. It's been running into the Jökulsár á Fjöllum, but the river is just yielding to the east.

The flow is expected to continue chasing the river northeast and pushing it further to the east, up until it reaches Vaðalda. There, according to Þorvaldur Þórðarson, it's expected to widen, not extending more than 20 kilometers long in that direction. A quick look at a satellite map reveals that the river flows through a small canyon at that point, which would be expected to restrict the flow.

The dangers of working at the eruption site seem to keep multiplying, because now the eruption itself is making its own weather which changes rapidly. Three times today scientists established positions for work that they thought were far enough away to be safe, only to quickly become overwhelmed by the toxic gas plume and have to flee. The national protective services is especially concerned by the media on the site, who isn't as used to working in these sort of conditions.

Speaking of making your own weather... remember that "fire tornado" spotted on infrared the other day, well now it comes in an IR video form. :)



Plus, here's some of those new-fangled non-moving pictures:















Oh, and as always, don't forget to check out those lava fountains on Mila - they were putting on a nice show this evening. :)

Update, 9:45: Several pieces of concerning news from last night.

First, tremor activity has been up, mainly on Vonaskarð and to a lesser extent Grímsfjall, but not Dyngjujökull. This suggests the possibility of a small eruption most likely in the caldera, or at least lava-groundwater interaction. The tremor is still high, so this is still an evolving situation. More news when it comes.

Secondly, all of you who noticed the increasing height of flames and darkening plume on Holuhraun? You were right to be concerned. First off, the scientific team reported an increase in SO2 degassing from the vents and haze on site - as if that problem wasn't already bad enough. Secondly, the geologists experienced tephra fallout 7 kilometers northeast of the fissure, with pumice up to 4 centimeters. Not only does this represent an increasing danger to their shelter at Dreki, but it also means increasing risk of an ash cloud that could interfere with air traffic; I'm going to have to start monitoring this aspect. I don't expect serious problems yet, but the situation could evolve further.

The mobile radar which you've all nicknamed R2D2 may get its opportunity to prove its worth soon.

Concerning earthquakes, since 6 AM Sunday we had a 5.4, a 5.2, a 5.0, a 4.8, a 4.6, a 4.5, a 4.3, a 3.8, and a 3.7. Most of these in the past 24 hours.

And just to top it all off? There's a new sigkatli in Dyngjujökull. Thankfully this one is closer than the other two to the foot of the glacier, 2-3km vs. 6km and 10km, respectively.

Lastly, I just wanted to mention something that I and the met office have noticed for the past couple days. It's not concerning at this point, but bears mentioning: there's been a small but consistent earthquake storm in Herðubreið - nor Herðubreiðartögl, but the tuya itself. I don't see any cause for worry at this point, but I do think it's worth mentioning - it's funny because the stress on the Askja system has been down for quite a while, so I'm not sure why it'd pick now to start rumbling.

Update, 11:30: Having trouble keeping up with all of the news. Rifting is progressing northward at Bárðarbunga. Also, the first pseudocrater eruptions have begun from the lava flow interacting with the river. Speaking of rivers, when the lava flow gets to the Jökulsár tributary Svartá, it's expected to dam it and likely destroy the waterfall Skínandi ("shining"). Map here. Picture of the likely-doomed waterfall here. A new lagoon is expected to form, which would either fill this winter or next summer.

Tremors continue at Vonaskarð and Grímsfjall. There's now a small uptick at Dyngjujökull.

Update, 14:30: And so I have to raise the question in bold: Why on earth is the airport at Egilsstaðir still open?