Flash flood alert at Markárfljót and Fljótshlíð in Iceland.
The real flood is finally here...
Almannavarnir (Civil Defence Authority) in Iceland has issued a general urgent evacuation alert for Fljótshlíð - a scenic farming area southwest of Eyjafjallajökull due to major flooding.
Gígsjöull lets go - from visir.is
There were two previous flood surges yesterday, but it was known that the bulk of the ice cap was still in place, melting.
The few km3 of water had only two places to go - it could go up, as steam explosions carrying ash, or break out sideways and come down the mountain, either to the northwest or the south.
It has now let got - much larger flood is coming down this evening with large ice chunks.
The evacuation area has been significantly expanded with a "run now, to higher ground" alert issued. Highway 1 is virtually certain to be cut along the south coast, possibly for an extended period.
Levees protecting farms that held in the first floods have now breached.
This is getting interesting, what with the disruption to air traffic and moderate ash fall.
The good news is that if the water came down the mountain, there is less in the caldera to drive major phreatic eruptions - those are the ones that send the huge ash plumes up to the stratosphere and hence around the globe - they are basically cubic klick of lava flash vapourizing cubic klicks of water, with aerosolized rock carried up as ash.
With much of the water gone in the flood, there is less danger of further major ash eruptions to high altitudes, for now, and better chance of the ash raining out and leaving North Atlantic air corridors safe for transatlantic flights.
The ash is relatively rich in hydrogen fluoride - which is soluble and biomobile. The ash is acrid, and you don't want it on your skin, but significant ashfall can lead both to acute toxicity, and, more seriously, to uptake in crops and toxic levels in food and feed crops.
Fish are also being killed in significant quantity in nearby rivers.
With the breach of the roads along the south coast, Vík í Mýrdal, the largest village under the glaciers, has run out of food and other consumables, and groceries are being shipped in - it really is true, that towns only have 3 days of food storage on average.
I was very impressed with the air traffic closure - it is in fact a major rationale for the Icelandic sector of the North Atlantic Air Traffic, that they cover these contingencies, and I knew they had both general contingency plans and that they had developed specific contingency plans for these eruptions that were continuously updated, but they worked, and were actually implemented in a timely manner with compliance!
That is actually quite astonishing, that several hundred flights can be immediately diverted or turned, as well as future flights.
It is a lot less bother than to suffer a total engine shut down at 36,000 feet over the middle of the ocean.
Fljótshlíð during better days - glaciers in the background - from ismennt.is - Jónas Gunnlaugsson
Martkárfljót from wiki
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