Tuesday, April 20, 2010

More About the Volcanic Cloud

Which is more unpredictable:

Eyjafjallajökull or

The human reaction to the ash in the air?

The airlines started complaining. Some airlines made empty plane trips, some at low altitude through areas where the cloud exists. No obvious damage.

So the European flight controllers said they would designate the airspace above the continent into three zones — one closest to the volcano where air traffic would be completely restricted, another zone with partial flight restrictions, and a third zone, free of ash, where flights could resume completely.

They no sooner made announcements about opening up a United Kingdom airport in Scotland, with the possibility of more airports in Wales and England, when the volcano in Iceland burped, and the situation for the airports in Northern Ireland was changed to "uncertain".

The official prognosis for Dublin Aiport was:

"Limited flight operations from Dublin Airport on Tuesday 20th April

The Irish Aviation Authority(IAA) have advised us that they expect to resume some air traffic services on a phased based from 05.00 , Tuesday 20th April. The IAA have also indicated that normal operations are not expected to be in place for up to three or four days."

But then after the volcanic burp, the announcement came out:

"06:30 hours: Latest on flight disruptions at Dublin Airport

The IAA have advised us that following a renewed eruption of the Icelandic volcano yesterday afternoon and prevailing weather conditions plans to open Irish airspace have been dashed.

The IAA have also advised us that Ireland is now at the centre of a contamination zone up to at least 1300 hours today, Tuesday 20th April.

This effectively means that no flights will land or take off at Dublin Airport today.

Passengers are advised to consult with their airline or airline’s website BEFORE coming to Dublin Airport."

Now my trip isn't for 2 weeks, but...I am beginning to wonder.

I didn't think about why Iceland is volcanic until recently. Iceland is on the mid-Atlantic ridge. The tectonic plates are moving apart, thinning the crust. This allows lava to reach the surface. Iceland has more than 100 volcanoes, of which over twenty five have erupted in recent history. Iceland is so active with volcanoes, approximately a third of the lava erupted in the last 500 years has erupted there.

This eruption is considered sub-glacial, or under glacial depth ice. Iceland has 83 percent of the worlds sub-glacial eruptions.

This present eruption converted into a sub-glacial eruption. When a volcano happens under a thick layer of ice, interesting things happen.

The one that matters with regard to this cloud is that the ice turns to water and the ice and water become shallow enough to erupt explosively. Not the kind of eruption where the whole top of the mountain is thrown in the air, but where the magma (really hot lava) cools rapidly, forming a kind of glass, and the magma cracks allowing the water to penetrate further. The process starts to feed itself - more water - more cracks. The magma is cooling but since it started out so hot, it has plenty of heat to turn a whole lot of water to steam in a hurry. This steam escapes in a hurry carrying loose ash it picks up with it, sending the ash high in the sky.

A competing theory is that there is "explosive thermal contraction of particles under rapid cooling from contact with water." I'm not sure how that works because contraction implies shrinkage, not expansion, but most geologists think both happen anyway.

Since water is consumed in the process, I don't see how this can go on too long. But if new areas of ice are contacted, or fresh volumes of magma rise...

So we sit and wait while the volcano reminds us we live at the mercy of forces beyond our ability to influence or control.

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