{"id":659,"date":"2012-05-22T13:09:50","date_gmt":"2012-05-22T12:09:50","guid":{"rendered":"http:\/\/all-geo.org\/volcan01010\/?p=659"},"modified":"2012-05-22T13:09:50","modified_gmt":"2012-05-22T12:09:50","slug":"happy-anniversary-grimsvotn","status":"publish","type":"post","link":"https:\/\/all-geo.org\/volcan01010\/2012\/05\/happy-anniversary-grimsvotn\/","title":{"rendered":"Happy Anniversary Gr\u00edmsv\u00f6tn"},"content":{"rendered":"

Yesterday was the first anniversary of the 2011 eruption of Gr\u00edmsv\u00f6tn.\u00a0 Despite being the largest eruption in Iceland in 50 years, the day passed without much fanfare as the eruption had a relatively small impact compared to a certain other eruption the year before.\u00a0 To understand why, read my post from the second anniversary of that one: An Icelandic eruption 100x more powerful than Eyjafjallaj\u00f6kull<\/a>.<\/p>\n

In this post, I want to point out the interesting effects that wind patterns had on the tephra<\/a> dispersal from the Gr\u00edmsv\u00f6tn eruption, and to update you on the analysis of the samples.<\/p>\n

Where to go: Greenland or Great Britain?<\/h3>\n

The US National Oceanic and Atmospheric Administration (NOAA) have a webpage where you can have a go at running their HYSPLIT atmospheric dispersion model<\/a>.\u00a0 This uses information on wind speeds and directions to predict where particles in the atmosphere will travel.\u00a0 It works in forward or in reverse, so if you smell a bad smell, you can find where it came from and if you make a bad smell, you can see where it is going to go.\u00a0 Except on a global scale.<\/p>\n

The Gr\u00edmsv\u00f6tn 2011 eruption was interesting, because the final destination of the erupted material was controlled really strongly by the height that it reached in the plume.\u00a0 Check out these two plots for comparison:<\/p>\n

Material from 8ooo m goes north<\/h4>\n
\"\"<\/a>

HYSPLIT trajectory for particles released at 8000 m. These do not include particle settling, but give a good idea of wind direction. Material is carried north across Iceland, then across to Greenland.<\/p><\/div>\n

Material from 4000 m goes south<\/h4>\n
\"\"<\/a>

HYSPLIT trajectory for particles released at 4000 m. These do not include particle settling, but give a good idea of wind direction. Material is carried south across Iceland, then across to Great Britain.<\/p><\/div>\n

Where did the tephra go?<\/h4>\n

The plume from Gr\u00edmsv\u00f6tn reached 20 km in altitude, but it turns out that not all of this was tephra.\u00a0 Much of it was steam and volcanic gas.\u00a0 To see whether most of the tephra was in the upper or lower part of the plume, have a look at this photograph of the area south of the crater, taken on an monster-truck expedition to the crater<\/a> last August.<\/p>\n

\"A<\/a>

A black sandy desert. This is the tephra deposit from Gr\u00edmsv\u00f6tn 2011 on top of the Vatnaj\u00f6kull glacier. All this should be white ice and snow. Click the image to read my post about a trip to the crater last summer.<\/p><\/div>\n

It is clear from the deposits on the ground that most of the tephra from the eruption was carried to the south by low-level winds and was deposited from the lower part of the plume.\u00a0 There was very little tephra deposited to the north of the crater, but material from the upper plume was carried carried to the north and was detected over Greenland by satellites sensitive to the volcanic gas sulphur dioxide (SO2<\/sub>).<\/p>\n

This complicated dispersal of volcanic material is another reason why mapping volcanic ash clouds is HARD<\/a>.\u00a0 The main lessons that were learned are:<\/p>\n