Monday, February 27, 2012

El Hierro Eruption Continues At Low Level

While the harmonic tremor readings are nearly flat, and visuals on the surface of the ocean have been few and fr between, the El Hierro submarine eruption is continuing at a low rate. For the last few days, the "jacuzzi" and stain area have made faint appearances, and water temperatures over the vent are still high enough to generate a steamy haze over the vent area. Today the jacuzzi area is a bit stronger, even though harmonic tremor is about the same as it has been for the last week or so.

The earthquakes to the West of the eruption zone have been continuing, varying from up to 20 quakes per day, down to a low of about 7. They are getting shallower in this area, indicating the possibility of more magma movement possibly to a different area. This could explain why "Bob" (the unofficial name for the submarine volcano) has shown minimal activity, because magma may be finding another route through the crust. It could also be that "Bob" is simply re-pressurizing, and the renewed jacuzzi and heat activity could indicate that the cone itself is heating up again and getting ready for another round of eruptive activity. Only time will tell. This could simply be underwater cooling and degassing, but this would not account for the activity today (the ocean is a GREAT heat sink, especially for cone building events such as this).

There have been regular scientific expeditions to the eruption area, with several scientific vessels taking bathymetry readings, and sonar scans of the ocean floor. From what I've read on Earthquake-report.com (they are fortunate enough to have a local reporting for them and taking daily photos), an ROV missions is planned in the near future to take direct video of the vent area, however due to currents and sometimes bad weather, they haven't had much luck getting the remotely operated vehicle deployed yet (they are insanely expensive, so they will always err on the side of caution when it comes to this equipment).

So until we have direct observations from the sea floor, it is hard to tell what the state of the eruptive cone is in at this time. All we can infer from tremor, and surface observations is that this eruption is continuing at a low level as it has been for the past week or so. This could change at any time.

In a previous post about El Hierro, I pointed out the similarities between El Hierro and the Hawaii island chain. While Earthquake-report.com picked up on this idea as well, they erroneously compared this eruption to that of Kilauea, instead of its newer and less active neighbor, Loihi. The surface eruption on Hawaii's Kilauea volcano is unimpeded by ocean water, and is able to create stable channels for lava to flow onto the surface. Loihi (first detected in eruption in 1996) is a submarine volcano SW of the Kilauea summit, and has periods of activity followed by long periods of dormancy, and has a lot of the same characteristics of the El Hierro submarine eruption.

While it is my belief that El Hierro, like Hawaii, is a "hot spot" type volcanic system, the dynamics are different from Hawaii. The chemical makeup of the lava is different, the location is certainly different, and instead of an underwater shield volcano (like Loihi), this seems to be a mere cone building event not separate from the main volcanic system at El Hierro.

Hot spot volcanic systems like the Hawaiian and the Canary islands can have long period of eruption like Kilauea, or short periods of strong activity... really the range of activity these spots are capable of is huge. El Hierro might be entering a phase of long term activity given the quakes, their locations, and the duration of what people thought was probably going to be a very small event. This is a volcano still worth watching, and is of great scientific interest.

*****UPDATE 2/27/2012*****

Activity at El Hierro is unchanged. Low and almost nonexistent harmonic tremor, coupled with light degassing and small jacuzzi visible. Probably the actual eruption of "Bob" the underwater cinder cone is over. However GPS data indicates uplift of the island of El Hierro itself, and quakes are clustering at the northern end of the island. El Hierro appears to be inflating, and it is not unreasonable to think that another cone building event, possibly on the island itself, may occur in the future. When is impossible to say.



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