{"id":787,"date":"2011-04-06T04:45:29","date_gmt":"2011-04-06T02:45:29","guid":{"rendered":"http:\/\/icelandgeology.net\/?p=787"},"modified":"2011-04-07T02:18:52","modified_gmt":"2011-04-07T00:18:52","slug":"deep-earthquake-in-hofsjokull-volcano","status":"publish","type":"post","link":"https:\/\/icelandgeology.net\/?p=787","title":{"rendered":"Deep earthquake in Hofsj\u00f6kull volcano"},"content":{"rendered":"

Among the most quiet volcanoes in Iceland is Hofsj\u00f6kull volcano<\/a>. It has not erupted in at least 12.000 years from it’s main crater (far as I know). But minor fissure eruptions have taken place in the last 12.000 years in the area around Hofsj\u00f6kull volcano. But they are undated far as I know. Because of that it is now known when the last eruption took place in Hofsj\u00f6kull volcano. In terms of Icelandic volcanoes, Hofsj\u00f6kull volcano is more complex then most. South of it lies the Kerlingafj\u00f6ll volcano. A volcano known for it’s heavy hydrothermal activity. But Kerlingafj\u00f6ll volcano has not erupted in historical times in Iceland. But they might have erupted in the last 12.000 years without me knowing about it. In the case of Hofsj\u00f6kull volcano looks are deceiving. According to a geological map that I have of Iceland, in the case of Hofsj\u00f6kull volcano it has a second magma chamber and a central volcano inside the SW part of it. That volcano is unnamed for oblivious reasons. That volcano might well behave differently then Hofsj\u00f6kull volcano it self. But I would theorise that this intergrated central volcano inside Hofsj\u00f6kull volcano is going to be active when Hofsj\u00f6kull volcano is.<\/p>\n

The icecap in Hofsj\u00f6kull volcano is deep. At it’s deepest point it is 650 meters deep at the most. The deepest points of the icecap are in the main caldera of Hofsj\u00f6kull volcano. If Chait\u00e9n volcano<\/a> in Chile has teaches geologist anything. It is that a long dormant volcanoes don’t need a long time to go from dormant to active eruption. That is why I find it worrying that deep earthquakes have started to appear in Hofsj\u00f6kull volcano, even if they are extremely rare so far. <\/p>\n

Over the past ten years or so there has been a slight increase in earthquake activity in Hofsj\u00f6kull volcano along with increase in hydrothermal activity. But so far it has just been a minor earthquakes. The strongest ones getting up to ML3.0 at the strongest. No earthquake swarm have ever been recorded in Hofsj\u00f6kull volcano to my knowledge (since recording begin in Iceland).<\/del>. Last earthquake swarm was recorded in Hofsj\u00f6kull volcano in the year 1999, then a earthquake swarm of 22 earthquakes took place, all of those earthquakes where just minor earthquakes. Besides being one of Iceland largest volcanoes, its location also makes it extremely dangerous. As it is located in the middle of Iceland, and a glacier flood from it could go many different ways down to the ocean and over large populated areas in Iceland. The increase in hydrothermal activity started in Hofsj\u00f6kull volcano in the year 1994 or about that time. It was at least first documented in that year. A sulphur smell was recorded when the homoeothermal vent was checked out that year in Hofsj\u00f6kull volcano. Increase in hydrothermal activity in Hofsj\u00f6kull volcano is interesting as it is followed by a slight increase in earthquake activity over a long period of time.<\/p>\n

\"\"<\/a>
\nLocation of the two earthquakes. The deep earthquake is the one closer to the caldera. This picture is from Icelandic Met Office web site. The copyright of this picture belongs to them.
\n<\/em>
\nThe earthquake that started me to get worrying about Hofsj\u00f6kull volcano is the earthquake that took place 10:11 UTC on 5. April 2011. That earthquake had the depth of 27.6 km. It’s size was ML1.4, so it was a small earthquake. I do not believe that this depth is a result of a error in the SIL system (can happen sometimes). A second earthquake took place at 10:13 UTC, its size was ML1.6 with the depth of 1.6 km.<\/p>\n

Whatever that is happening in Hofsj\u00f6kull volcano is worth watching. Even if it not going to erupt just yet. It is also my opinion that Hofsj\u00f6kull volcano is not part of Western Iceland Rift Zone<\/a> (pdf). But its is the most southern part of a failed rift zone often called Skagafj\u00f6r\u00f0ur volcanic zone<\/a> (pdf). It is a failed volcanic zone that is mostly extinct, only Hofsj\u00f6kull volcano and Kerlingarfj\u00f6ll volcano remain active in that volcanic zone at the most southern end of it.<\/p>\n

Other information.<\/p>\n

Jar\u00f0hiti \u00ed Hofsj\u00f6kli<\/a> (T\u00edmarit.is, Icelandic, 1996, pdf) – Article with picture of where the hydrothermal vent was found in Hofsj\u00f6kull glacier.
\nHofsj\u00f6kull<\/a> (Wiki, english)<\/p>\n

Text updated at 18:11 UTC on 6. April 2011. Minor fixes in the text.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Among the most quiet volcanoes in Iceland is Hofsj\u00f6kull volcano. It has not erupted in at least 12.000 years from it’s main crater (far as I know). But minor fissure eruptions have taken place in the last 12.000 years in the area around Hofsj\u00f6kull volcano. But they are undated far as I know. Because of … <\/p>\n

Continue reading “Deep earthquake in Hofsj\u00f6kull volcano”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10,29,32],"tags":[],"class_list":["post-787","post","type-post","status-publish","format-standard","hentry","category-earthquakes","category-hofsjokul","category-volcano"],"_links":{"self":[{"href":"https:\/\/icelandgeology.net\/index.php?rest_route=\/wp\/v2\/posts\/787","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/icelandgeology.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/icelandgeology.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/icelandgeology.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/icelandgeology.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=787"}],"version-history":[{"count":10,"href":"https:\/\/icelandgeology.net\/index.php?rest_route=\/wp\/v2\/posts\/787\/revisions"}],"predecessor-version":[{"id":798,"href":"https:\/\/icelandgeology.net\/index.php?rest_route=\/wp\/v2\/posts\/787\/revisions\/798"}],"wp:attachment":[{"href":"https:\/\/icelandgeology.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=787"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/icelandgeology.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=787"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/icelandgeology.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=787"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}