Sorry about the lack of posts - the holiday and "real life" had stepped in the way.
On with the news!
Mayon Volcano in the Philippines with Legazpi City in the foreground.
Mayon, one of the most active volcanoes in the Philippines, is causing concern due to increasing signs of activity. Renato Solidum, the director of PHIVOLCS (Philippine Institute of Volcanology and Seismology), said that there has been increasing seismic activity and "glow" at the summit of the volcano near (~20 miles / 45 km) Legazpi City. However, even after this sense of increasing activity, the alert level (1) has not changed, but local residents were altered to the new activity. This means that there is low-level unrest with slight increase in seismicity. The last notable eruption in 2006 at Mayon (oddly called a "silent eruption" in the linked article) produced a lava flow. There were also minor phreatic explosions in 2008.
Mayon seems to be one of the steepest and picturesque volcanoes that I have ever seen.
It is good that the local residents in the area were alerted - because in the event of a major eruption - we don't want them to become âalteredâ too much!
Does anyone know why Puerto Rico always has so many earthquakes? Will the steep subduction zone off the coast produce a volcanic eruption in the area?
As an attempt to answer Thomas' question about Puerto Rico:
The tectonics in the Caribbean basin are really complex. You can see in the map below that there is active subduction along the West Indies that produce volcanism in places like Montserrat and Martinique. Puerto Rico is to the north and west of the West Indies, along an area where the plate boundary of the Atlantic Plate and Caribbean Plate are behaving more like a transform boundary. This might be the reason why there are so many earthquakes near PR rather than any volcanism.
Caribbean tectonic map: http://upload.wikimedia.org/wikipedia/commons/4/49/Caribbean_plate_tect…
You can really see how PR is bounded by transform faults on this map:
There is some more info on the PR area and the related tectonics over on Clastic Detritus: http://clasticdetritus.com/2008/02/03/sea-floor-sunday-10-puerto-rico-t…
I found the links helpful Erik.
The mystery though is now even deeper for me. If the area to the east of Puerto Rico appears to be a transform boundary - then why is there such a big trench there? Aren't subduction zones associated with trenches? - Or is there another explanation? A link from one of the links that you provided - adds to the mystery - the scientists seem baffled about something.
They write about the area, â...scientists have so far failed to explain the deformation of this complex region in a coherent and predictable picture, and this has hampered their ability to assess the seismic and tsunami hazards. It is as if we would try to assess earthquake hazards in California without knowing of the existence of the San Andreas Fault system and its rate of motion.â
I wonder if a deep, large magma source could be forestalling the subduction at this time? The Yellowstone hotspot exerts pressure that overrides local faults.
I am not arguing that it is at all likely that this is the case at Puerto Rico. But since the scientists can't account for the current âdeformationâ of the area with the normal theories they need to re-examine their assumptions, consider new ideas - even volcanism.
If this area has not been prone to volcanism in the past - and if this is volcanic pressure building deep below - an eruption here would be very dangerous.
Unless I am missing something - this picture of the Puerto Rican trench not subducting - is very, very wrong - or very dangerous.
From the link provided by Erik,
âThe Puerto Rico Trench reaches water depths greater than 8 km making it the deepest part of the Atlantic Ocean (the Marianas Trench gets to 11 km in case youâre wondering). The North American Plate is subducting underneath Caribbean Plate.â
Nothing like the unseen hand of large volcanic forces to throw a monkey wrench into what might otherwise be a simple subduction zone.
Is this a valid hypothesis? That the zone was subducting - but right now pressure from magma is deflecting the subduction forces and causing them to instead move like a transform fault?
Some thoughts are too terrifying to state as likely. However, has there been any analysis of the speed that earthquake waves travel through the area? Slow speeds correspond with magma.
I just want to make clear that I am not asserting that there is any volcanic stirrings under Puerto Rico - but the deep trench off of Puerto Rico leaves me wondering how it formed. Are there any oceanic trenches around the world that are not associated with subduction and volcanism?
I would like to be able to rule out any emerging magma system under Puerto Rico. Is there any way to prove that there is not a deep magma source rumbling deep under Puerto Rico? The earthquakes in the area plus the subduction zone makes me wonder.
Perhaps there is just a complex buckling of plates and parts of tectonic plates that is accounting for all this. Still, I'd like to figure out why is there a deep trench off of Puerto Rico. Am I reading the map wrong? If there is a subduction zone - are there any rules or principles that pertain to whether or not volcanic activity will develop.
I just now found that there is âa probable extinct mud volcanoâ in the deep off of PR. (Is the extent of PR volcanism?) See point âBâ on this map.
I appreciate you all putting up with my wrestling with a variety of volcanic issues.
I'm still learning from you, but I'm trying to achieve my goals. I certainly enjoy reading all that is written on your website.Keep the stories coming. I enjoyed it