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Ethiopian eruption: scientists on ground, shoes melt 13 July 2009

Posted by admin in activity reports, Africa, eruptions, Ethiopia, Manda Hararo.
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The first on-the-ground reports from the location of the recent eruption in the Manda Hararo volcanic field in Ethiopia have come from David Ferguson, a doctoral student in geology at the University of Oxford. He is reporting on his work on the volcanics of the Afar region in a series of blog postings for The Guardian.

Part 1 describes how he dropped everything and flew out there to take a look at what was going on, part 2 and part 3 (with photographs, including a wonderful aerial view of an eruptive fissure) see him reach the location courtesy of the Ethiopian Army, while part 4 (with more pictures) is an account of what he found once he got there with his Ethiopian colleagues:

As we reached the front of the lava flow one of our group, Dr Elias Lewi, walked out over its brittle surface, quickly turning back as his shoes begin to melt. Although only a few days old, the lava had a dark black crust and was deceptively similar to other, much colder flows. The real temperature was revealed by Talfan Barnie, a PhD student from Cambridge, who used a thermal infra-red camera to ‘see’ temperatures of up to 162C around the cracks and fractures across the flow surface.

We had to be very careful where we trod.

David Ferguson reports extensive (~10 square km) fresh lava flows from the eruption, about 3 m high at the margins, gas emissions, and a 5-kilometre fissure and central vent producing a small plume. There is more on Manda Hararo in the Global Volcanism Program’s Weekly Volcanic Activity Report for 1-7 July.

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Saudi tremors continue: return of evacuees delayed 25 June 2009

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The earthquakes in Saudi Arabia may have dropped out of the news recently, but the activity has been continuing. The return of residents evacuated from the Al Ais area of western Saudi Arabia has been indefinitely postponed following the occurrence of significant tremors over the past few days, reports the English-language Saudi daily Arab News:

The decision follows the relatively high intensity of tremors registered over the past two days, he said. According to an SGS bulletin issued yesterday, the National Network for Seismic Monitoring, a subsidiary of SGS, registered two tremors measuring 4.55 and 3.2 on the Richter scale in addition to several lesser tremors during the 24 hours ending noon yesterday.

Meanwhile an intriguing (if rather vague) story from the Saudi Gazette quotes a Saudi Geological Survey report that ‘geologists discovered the detachment of a large chunk of a mountain in Harrat Al-Shaqqah from the main mountain mass as the result of the widening of the faults in its base’, and gives the explanation of geology professor Dr Abdul Aziz Bin La’boon for the Al-Ais activity: ‘molten rocks under the ground tried to push their way to the surface through the channels used by old volcanoes that erupted earlier, but due to their old age the rocks had solidified, so the current molten rocks are trying to find a new way out’.

News
Earthquake threat persists in Al-AisArab News, 31 May 2009
SGS issues statement on Harrat Al-Shaqqah tremorsSaudi Gazette, 12 June 2009
Return of Al-Ais dwellers delayedArab News, 24 June 2009

Information
Global Volcanism Program: Harrat Lunayyir – information from the GVP on the area where the seismic activity has been located
Global Volcanism Program: Arabia – information from the GVP about the volcanoes of Arabia

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Yellowstone updates from the YVO 9 January 2009

Posted by admin in activity reports, calderas, United States, Yellowstone.
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The Yellowstone Volcano Observatory (YVO) has released two new statements on the earthquake swarm that rumbled its way through Yellowstone in late December and early January.

The 6 January 2009 YVO update reports:

About 500 earthquakes occurred between Dec. 26 through Jan. 1. Three hundred of the earthquakes (including all >M2.0) have been reviewed by seismologists. There have been 86 earthquakes with M > 2.0 and 16 earthquakes > M3.0. About 200 smaller earthquakes have yet to be reviewed. Depths are difficult to determine accurately. The best located earthquakes have depths on the order of 3 to 10 km (1.8 to 6.0 miles). From Dec. 26 through Jan 2, the earthquake hypocenters appear to have migrated northwards, starting southeast of near Stevenson Island, with many of the latest events occurring near Fishing Bridge.

The recent swarm is well above typical activity at Yellowstone. Nevertheless it is not unprecedented during the last 40 years of monitoring. Swarms are the typical mode of occurrence of earthquakes within the Yellowstone caldera, with magnitudes ranging to > 4.0. The 1985 swarm on the northwest rim of the caldera lasted for three months, with earthquakes up to M4.9 and over 3000 total events recorded.

Magnitudes of earthquakes in this swarm range from zero to 3.9.

A further summary statement on the swarm, with graphics, was released by the YVO on 8 January 2009:

About 900 earthquakes occurred between Dec. 26, 2008 and Jan. 8, 2009 in the Yellowstone Lake area. Five hundred of the earthquakes (including all greater than magnitude 2.0) have been reviewed by seismologists. There were 111 earthquakes with magnitudes greater than 2.0 (> M2.0)and 18 earthquakes > M3.0. About 400 smaller earthquakes have yet to be reviewed. The largest earthquake during the swarm was a magnitude 3.9 on Sunday, December 28, 2008. […]

The recent swarm is well above typical activity at Yellowstone. Nevertheless it is not unprecedented during the last 40 years of monitoring. Earthquake swarms within the Yellowstone caldera are typical, with magnitudes occasionally ranging above 4.0. The 1985 swarm on the northwest rim of the caldera lasted for three months, with earthquakes up to M4.9 and over 3000 total events recorded.

With analysis of earthquakes and of ground motions accompanying the swarm still in progress, this is very much a preliminary report. No conclusions as yet, then, about the cause of the swarm, only the important negative conclusion that ‘there is no reason to believe that magma has risen to a shallow level within the crust or that a volcanic eruption is likely’.

Full statement: Yellowstone Lake Earthquake Swarm Summary as of 8 January 2009.

There’s also a new USGS CoreCast featuring an interview with Dr Jake Lowenstern, Scientist-in-Charge at the YVO, who talks about what’s been happening at Yellowstone and the work of the YVO in monitoring activity and keeping people informed. Dr Lowenstern has this to say about the earthquake swarm:

This is a very energetic swarm, and probably the most energetic swarm since 1985. So, it’s not unprecedented, on the other hand, it’s an energetic swarm, people were feeling it, and it’s an area where there are thermal features, and anytime there’s earthquakes near thermal features we worry about explosions of the groundwater system.

Dr Lowenstern also has some interesting comments about the explosion of information and speculation about this kind of event made possible by the internet, and where this leaves professional scientists concerned that information is used in a responsible way:

One of the amazing things we see during these kinds of events is how many people are out there looking at the data and trying to interpret it on their own. Sometimes they do a great job of it, sometimes they confuse other kinds of signals like wind and snowmobiles and other features that might look like earthquakes but indeed might not be earthquakes. So it’s a challenge for us not only to keep up with the science, but to keep up with the sort of furore out there, of people who are trying to do their own interpretations on the side, and to keep everybody happy and everybody thinking about the real endgame, of making sure that people are safe.

The USGS CoreCast interview with Dr Lowenstern is  available through this page: Is Something Brewing in Yellowstone?

Information
Global Volcanism Program: Yellowstone – information about the Yellowstone Plateau volcanic field (1205-01-)
Yellowstone Volcano Observatory – monitors activity at Yellowstone
University of Utah Seismograph Stations – UUSS home page, including Yellowstone updates
Yellowstone Region seismogram displays – near real-time seismogram traces for Yellowstone
USGS earthquake list for Yellowstone – constantly updated earthquake data for Yellowstone

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