seismology

The Eyjafjallajokull Eruption Illustrated

As a companion to this post, there is a short google earth tour that will enable you to explore the eruption area in Iceland, and fly to other eruption sites of the past.

To access the tour, first download Google Earth, then download this KML file, and finally double click the video icon in the places menu.

There was significant volcanic eruption in this morning between the Eyjafjallajokull & Myrdalsjokull Glaciers in Southern Iceland. The eruption brought about a glowing, thick, viscous lava flow through the glacial ice and left a plume of smoke and steam more than a kilometer high.
The eruption forced a prompt evacuation of nearby villages, including farming villages Hvolsvollur, Vik, and Skogar. Skogar is a sleepy town of herders, which occasionally attracts wayward, glacier bound tourists, to the local folk museum, shown below. I’ve never seen a photograph, which did less to dispel those elvish stereotypes surrounding Icelanders.
This eruption will not threaten human lives. Abandoned livestock are the most at risk from the gases. It is the flooding that follows that will cause the most problems. The volcanic runoff and heat from the eruption could create spouts of hot water that may melt the glacier.
The biggest threat, in this scenario, would be is a subsequent eruption of the nearby Katla Volcano, a few miles to the northeast, underneath the Myrdalsjokull Ice Cap. Such an eruption would melt the cap and set off catastrophic flooding.
Hopefully, history will not repeat itself, but the odds are not in the Icelander’s favor. According to wikipedia: Over the past 1,100 years, Eyjafjallajokull has erupted three times: in 920, 1612, and between 1821-1823. Each of these incidents directly preceded a major eruption in the nearby subglacial volcano,Katla.[9]

 

The Hekla Volcano, above, is proof in itself why Iceland is such a captivating location for scientists and ecotourists, alike. These eruptions should only add to the mystique.















Our fingers here are crossed that Iceland can escape without a second eruption, and that this video is the worst of the damage. The Icelanders had a rough 2009, highlighted by the crash of their banking system. An eruption at Katla would make those problems seem as far off as Bjork’s time with the Sugarcubes.
Now, if they’d only stop selling whale at the supermarkets in Reykjavik…

This post was made possible by information from theSmithsonian’s Global Volcanism Program

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Geocurrents on Mars- A 3D Tour of the Red Planet in Google Earth

This weekend’s Google Earth adventure on Geocurrents will take us to a place colder than Svalbard or the Ross Ice Shelf, and dustier than the Namib, Nefud, or Taklaman Deserts.

With sweeping dune fields, seismic chasms, deep double impact craters, and a monolithic human face; Mars is a geographer, topographer, seismographer, hydrologist, and conspiracy theorist’s delight.

Provided for you, below, is a smooth, short narrated flyover tour of the red planet. The tour highlights the planet’s topographical features, including: the first man made object on mars, dune fields, polar ice caps, rover sites, canyons, dried riverbeds, and the captivating ‘Cydonia’ formation.


If you’re already comfortable with Google Earth,
download the video tour and waypoints here. Otherwise, instructions on accessing our Martian tour are provided below.

First, download and install a copy of Google Earth.

Once you’ve loaded the program, switch your Google Earth browser into Mars mode. You can do this by using the explore tab in the view bar, as shown below:

Next, download this file, which contains both the narrated guided tour, and our waypoints. To play the tour, double click the video reel in the sidebar. The tour is at its most awe inspiring when viewed in full screen mode with the sidebar disabled.


You may also explore the planet step by step by double clicking the waypoints to fly from feature to feature.

Make sure to stop and read the information linked to the featured landmarks. This information provided by NASA, Google, and the University of Arizona, will enhance your tour experience.

This tour marks giant leap for Geocurrents.info.

Happy flying!

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Haiti’s Quake History and Why the Dominican Republic Should Worry

Haiti sits between two massive seismic plates, the Gonave Plate, part of the larger North American Plate, and the Caribbean Plate to the south. The capital, Port Au Prince lies less than 20 km from the Enriquillio-Plaintain Garden Fault (EPGFZ), the a convergence point between the two plates.

This fault is a ‘strike slip fault,’ where there is a deep vertical fracture between the two paltes, and friction is accrued horizontally. The Haiti quake, was caused by the pressures from the eastward motion of the Caribbean plate, which moves as shown in the model below from Purdue University Seismologist Eric Calais.
This model, from Caltech’s Anthony Sladen’s source model, dramatically represents the what happened when these plates unstuck, by showing how the surface of the earth was displaced by the event.

The area has built up seismic tension, since the EPGFZ’s last series of quakes in the mid 18th century. There were three major seismic events in a twenty year span, as the seismic tensions was relieved through a series of quakes. Here is the recent seismic history of the region, via the University of Texas Jackson School of Geosciences.
Strangely enough, there quakes were predicted a year ago, yet there was little action taken. In 2008 Paper, presentation to the Caribbean Conference, Professor Calais predicted that Haiti was due for a magnitude 7 or earthquake, owing to the seismic pressure the Enriquillo Plantain Garden Fault had accrued a from ‘slip debt’ of over two meters. Take a look at this prediction from Professor Calais, who is earning a reputation as a seismological prophet:

We confirm that the oblique convergence between Caribbean and North America in Hispaniola is partitioned between plate boundary parallel motion on the Septentrional and Enriquillo faults in the overriding plate and plate- boundary normal motion at the plate interface on the Northern Hispaniola Fault. To the east, the Caribbean/North America plate motion is accommodated by oblique slip on the faults bounding the Puerto Rico block to the north (Puerto Rico subduction) and to the south (Muertos thrust), with no evidence for partitioning. The spatial correlation between interplate coupling, strain partitioning and the subduction of buoyant oceanic asperities suggests that the latter enhance the transfer of interplate shear stresses to the overriding plate, facilitating strike-slip faulting in the overriding plate. The model slip rate deficit, together with the dates of large historical earthquakes, indicates the potential for a large (Mw7.5 or greater) earthquake on the Septentrional fault in the Dominican Republic. Similarly, the Enriquillo fault in Haiti is currently capable of a Mw7.2 earthquake if the entire elastic strain accumulated since the last major earthquake was released in a single event today. (Source)


It is important that the world takes Calais’ warning about the Septentrional Fault, with a great deal of Urgency. The fault, which runs through the Northern Dominican Republic is due for a quake even larger than that which occurred in Haiti.
The Dominican Republic should learn all that it can from Haiti’s experience, as they are proverbially walking down a geological hallway with a large kick me sign affixed to their back.
Today’s 6.0 aftershocks, combined with the historical patterns of quakes appearing waves have raised suspicions that this only the beginning of a larger regional alleviation of seismic pressure. The aftershocks are shown below from the USGS’s nifty google earth quake tracker.

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