As the three remaining readers may have noticed, I've been a bit too busy to blog for a couple of weeks.
But other blogs go on, and right now, over on SciBling "Eruptions" there is a fascinating live discussion in the comments on the possibility of an imminent eruption in Eyjafjallajökull.
Increasing signs of activity at Eyjafjallajökull in Iceland
Click to embiggen
From Fosshotel - stay there, it is nice
See also aerial view from snorrason.is
Eyjafjallajökull is a small glacier just west of the medium sized Mýrdallsjökull which hosts the better known volcano Katla.
Eyjafjallajökull has its own, smaller, caldera which last erupted almost 200 years ago, and seems to have erupted every couple of hundred years ago in the last millennia.
The magma system is part of the fissure running from Heimaey up to Katla and on north, and is very active.
Since the volcano is sub-glacial, any significant eruption will be accompanied by flash melting and shattering of the ice cap, and associated jökulhlaup - the wall of water coming down as the eruption starts, which can be tens of meters high and scour a strip many kilometers wide, with peak flow levels larger than the Mississippi in full flood.
To make things more exciting, the magma system may be tightly enough coupled to Katla, that eruptions pair - Katla is bigger and meaner, and historically erupts a couple of times per century. It last erupted 92 years ago.
A couple of time per 100,000 years Eyjafjallajökull seems to undergo major explosive eruptions.
There has been a series of small earthquakes on the last few days, several hundred in the last couple of days. This is suggestive of a magma intrusion into fissures and chambers under the mountain.
Cumulative earthquake count (all magnitudes) From hraun.vedur.is
The earthquakes started at a depth of about 10km, but seem to have moved up in the last few days, pausing at about 7km, with some recent earthquakes about 2km down.
The spectral characteristics, sizes and time series are indicative of subsurface magma flows.
The earthquakes swarm died off a bit over the weekend, but anecdotal reports suggest it is starting up again.
Plot your own earthquake history at the Icelandic Meteorology Office
This could die off now, just a bit of subterranean rearrangement, but it could also be the immediate, and exquisitely recorded, precursor of an eruption.
GPS locators have shown significant surface swelling and shift, and pressure is definitely building up under the ice.
No word on whether acidity or sulphur content in the rivers flowing out from under the glacier has changed.
Almannavarnir.is have gone to "condition uncertain", lowest stage of alert, cautioned travelers and closed the road going up to the glacier (it is popular for extreme skiing and snowmobiling, last I heard).
Jón FrÍmann is blogging it, in between the political ruminations all Icelandic bloggers are currently indulging in,
he runs his own seismometer, interestingly close to the epicenter.
Hopefully this will be a big nothing, or at most a nice little "tourist eruption", suitable for overcharging geotourists to circle the caldera in small planes, and camp out on the west side of the glacier admiring the plume.
A real eruption is the last thing Iceland needs right now.
Next couple of days should be telling.
- Log in to post comments
More like this
"I'm just trying to think who the other two are."
Errm, Should those of us on the West coast of Ireland be looking at Tsunami preparations ?
Just to be clear, I do not mean, "OMG the world is about to end". I mean, who has a working Tsunami model of the North Atlantic you can check ?
If a radio station phones up the physics dept. and says "10 minutes ago there was an eruption in Iceland; should we worry about a tsunami?", is there an established tsunami forecast system we can check?
Alastair: I'm not an expert, but I don't see a mechanism that would produce a tsunami. To do that you need something that suddenly displaces a volume of seawater. The eruption itself, being on land, can't do that. If the mountain were close enough to the shore that the resulting landslide could fall into the ocean, that could produce a tsunami, but I gather from Steinn's description that the site is well inland.
I'm not aware of any working tsunami model in the Atlantic Ocean, mainly because tsunamis there are much rarer than in the Pacific. There was the one in Haiti that nobody noticed for several days after the fact, and I have heard of one produced by a landslide in the Canary Islands, but those are the only two I can think of offhand.
Wiki has the Tsunami warning centers:
http://en.wikipedia.org/wiki/Tsunami_warning_system
I don't think there is anything formal for the North Atlantic.
Eyjafjallajokull is not very big, not that steep and a good bit of sand (over 10 km wide strip, as I recall, though it varies a bit) between it and the sea.
Any southward explosion big enough to displace cubic km into the North Atlantic would probably get western Ireland directly, no need to wait for the sea.
I know Los Alamos did simulations of sea intrusion into suboceanic magma chambers (in the context of the 1973 Heimaey eruption) - can't have been very sophisticated, but they did conclude the displacement tsunami would take out west Ireland, and north east US/Canada.
There is a high repose unstable slope on the side of the Canaries, with a volcano behind it, if that goes, the east coast of the US is in bad shape, an also probably caribbean, don't know if diffraction or rebound would get Ireland/west Europe/Mediterranean.
I know Los Alamos did simulations of sea intrusion into suboceanic magma chambers (in the context of the 1973 Heimaey eruption) - can't have been very sophisticated, but they did conclude the displacement tsunami would take out west Ireland, and north east US/Canada.
I was looking for details of this earlier on. Wasn't there some sort of plan to divert the lava flow from Heimaey that turned out to risk blowing up the whole of Iceland and flooding New York into the bargain? I could find plenty of stuff about the lava cooling exercise, but I think this involved an explosion of some sort.
Hm, funny that - I got told the whole story in person one winter at the Aspen Institute - from the horse's mouth.
The cite is: "Dynamic mixing of water and lava" by S.A. Colgate and Th. Sigurgeirsson 1973, Nature 244, 552
Ãorbjörn Sigurgeirsson was a senior Icelandic geologist, he directed the ultimate "lava cooling" project, where basically high capacity water pumps hooked to fire hoses tried to cool edges of the lava flow to slow and redirect the flows, in order to save the critical harbour entrance at Heimaey.
Now, the officer in charge of the US base at Keflavik provided logistical support for this, and he and Colgate were buddies.
A previous suggestion to ameliorate the eruption had been to blow a whole in the side of Eldfjall and quench the lava directly. Probably using a smallish nuke.
The US was quite keen to try this.
Colgate, and I think Ãorbjörn independently realized that this was a bad idea, due to the above mentioned dynamic mixing.
Colgate, for reasons we don't need to go into, had been experimenting with the fizz-bang properties of alkali metals in water, and how the burning front went from a steady propagating coherent front to strongly mixed cascade where the interacting surface grew rapidly.
They realized this would probably also happen with water and lava leading to prompt disassembly of the island, and some hundreds of cubic km undergoing prompt displacement, under water.
That would be not good.
So they called off the operation.
And wrote a Nature paper, as one does.
Los Alamos revisited the Atlantic Tsunami issue in connection with the "Double Impact" movie scenario.
I want to say Jack Hills was involved in that, which suggests to me he was also involved in the original calculations in the '70s.
Some of their stuff is here:
http://t14web.lanl.gov/Staff/clm/tsunami.mve/tsunami.htm
yup, Mader and Hills.
Others have also done this of course, but I think Mader did a lot of the pioneering work.
I hadn't realised they were thinking about a peaceful nuclear explosion (best oxymoron evar!). That puts it into World of Charlie Stross Lovecraft/Cold War Modern territory (now what were they *really* worried about - under the sea...?)
It's a solution to the Icesave issue, I guess...
Imagining Stirling explaining that story in person is cracking me up!
I like the use of the word "interaction" in that link, as in:
The interaction of a May 23, 1960 tsunami wave with current Hilo, Hawaii tourist hotels.
Of course, in SF terms that's Ballard rather than Stross, especially the bit about tourists.
Also, try explaining it without using the phrase "earth-shattering kaboom":-)
It was an interesting evening.
Both Stirling and I were wounded in action, as it were, and had been skiing the lower gentler parts of Highlands, where we bumped into each other and skied together for a bit.
Conversation turned to what happens when you drop Na or K in water (why he did that is another story, involving a swimming pool and the difficulty of getting kg lots of alkali metals), and then Heimaey - over dinner at the Meadows.
Very interesting evening.
Ãorbjörn died too soon, it would have been interesting getting that group together for the 25th anniversary or something.
i thought that it would be about cats. there were no 'cats' mentioned in this artical!!! what is up with you guys lying!!!!! i want to know about cats!!!
There's cats, and there's Cats, and there's CATs
Plenty here. Even the occasional feline domesticus
Since Susie insisted: http://phoenixwoman.wordpress.com/2010/04/16/friday-cat-blogging-161/