Iceland's Seismic Activity: A Repeat Show for Atmospheric Ash? 69
In 2010, ash spewed into the atmosphere by the volcano beneath Iceland's Eyjafjallajökull glacier grounded European air traffic for days (and, partially, for weeks). As reported by The Guardian, a series of similarly situated earthquakes may herald a similar ash-ejecting erruption, and the country has raised its volcano risk to its second-most-severe rating (orange). From the article:
Iceland met office seismologist Martin Hensch said the risk of any disruptive ash cloud similar to the one in 2010 would depend on how high any ash would be thrown, how much there would be and how fine-grained it would be.
Bardarbunga is Iceland's largest volcanic system, located under the ice cap of the Vatnajokull glacier in the southeast of Iceland. It is in a different range to Eyjafjallajokull.
The met office said in a statement it measured the strongest earthquake in the region since 1996 early on Monday and it now had strong indications of ongoing magma movement.
"As evidence of magma movement shallower than 10km implies increased potential of a volcanic eruption, the Bardarbunga aviation colour code has been changed to orange," it said.
"Presently there are no signs of eruption, but it cannot be excluded that the current activity will result in an explosive subglacial eruption, leading to an outburst flood and ash emission." ...
Hensch said the biggest risk in Iceland itself was from flood waves from any eruption under the glacier. He said the area of Iceland mainly at risk of flooding was mostly uninhabited but that roads in the area had been closed.
Re:So I'm confused... (Score:5, Informative)
The roads are designed for flooding in Iceland (Score:5, Informative)
South of Vatnajokull is an area of gravel desert with little to no inhabitants. As there are frequent floods and ever changing "river" estuaries, all of the many small bridges in the region are specifically designed to be washed away easily. It's simply cheaper to build them new ones after every serious flood. The Icelanders know what they are doing!
Re:So I'm confused... (Score:5, Informative)
Actually, more to the point, that the ash cloud has dissipated so there's less of a threat. Because this was at the end of it and air traffic had been shut down for over a week and a half, so people were skeptical that things have changed so much that you couldn't fly yesterday, but you can today. (Plus, airline finances are such that if you're not flying them, you're losing money, so the CEOs were really desperate to get moving again and stem the losses).
Volcanic ash is still nasty stuff - it erodes surfaces and glasses up in engines, which causes them to fail. In fact we didn't know about ash clouds until the late 1970s when a 747 was barely able to land in Indonesia after all of its engines failed and won't restart (until the engines cooled to the point the glassed ash broke off AND they were below the ash cloud and could restore limited power). And on landing, they realized they couldn't see out the front windshield because the ash was like sandpaper to it.
The CEO show was basically to say that there wasn't enough ash to down your plane anymore and that it was safe to travel again. (Though I'm sure they probably called for extra inspections because of buildup could cause a failure later on down the line).
There is worldwide monitoring of ash clouds and all that because of that accident because it's still harmful. It doesn't happen TOO often that air travel has be diverted because of volcanic activity, but it's still something pilots avoid.
Re:So I'm confused... (Score:2, Informative)
No, that's not what happened. What they determined is better constraints on what ash concentrations are significant. There is still a hazard of engine shutdown and windshield frosting (decreasing visibility) if ash density is high enough, and besides those hazards, there were also questions about maintenance (i.e. not hazardous to the flight, but having a lot more wear-and-tear on the engines, meaning higher costs/maintenance). Starting out, regulators and airlines weren't sure where that threshhold was, and there wasn't much in-air calibration of what density was being picked up in satellite imagery. This all meant they had to err on the side of caution if any ash was present. Now that those threshholds and the image calibration are better established, the safety limit is set at a lower ash concentration than previously, which should make it easier to deal with. The aircraft will still have to avoid higher-density parts of the plume, and if the eruption is bigger than Eyjafjallajökull it might be a moot point.
Re:At least you can pronounce Bardarbunga (Score:4, Informative)
At least you can pronounce Bardarbunga.
It is a composite word: Bárður - A man's name. Bunga - In this context it means mountain or peak. So in English: "Bárður's Peak"