Pues viendo el estado de la caldera y el post de Jón Frímann, el colapso es inminente. Veremos al final cuando colapse que pasa, hacia donde sale todo y sus consecuencias.
Este fragmento está sacado del blog de Jón Frímann,.
crosspatch:
September 14th, 2014 at 01:35
I do not have a good feeling about the signs I am seeing but there is always the chance that it will just stop short of anything major. That’s the odd thing about volcanoes, they almost always do the unexpected. That said, this one has potential to have severe impact on the people in Iceland and beyond in a worst case scenario.
Things that bother me: First is the deflation of the main caldera. This is apparently due to migration of magma in the system under it as it has apparently found a path out to the Northeast. There could be a combination of both the relief of pressure under the caldera and a softening of some of the rock immediately above the chamber going on, I don’t think anyone can tell exactly how much impact that might have. The migration of new material up from deeper levels might cause a remelting of older magma that had solidified or mostly solidified.
Second we see inflation in various places such as the dike going Northeast from the main caldera which indicates magma is entering that area at a greater rate than it is leaving. The worry on my part comes in the case of a fracture in the rock in the main caldera due to the collapse that might cause the magma to find yet an easier path up than the current dike path. This could cause all that magma that has inflated the dike to come rushing back and be erupted out the caldera area.
The third worry is that fractures in the rock can allow a lot of water to penetrate deeply into the area of the caldera, contact magma, flash to steam, causing a further opening of the rock or causing an explosion resulting in a very quick reduction in material (ice, mostly but also some rock) acting as a cap over the caldera area.
The third item will be sort of hard to do because luckily the caldera is under hundreds of meters of ice. This creates a lot of pressure and at those pressures, water can remain liquid at very, very high temperature. The first indication of water penetrating into hotter rocks would be some geothermal activity such as increased fumerole activity, appearance of new fumeroles where none existed before, or appearance of “cauldrons” where we see depressions forming from the melting of ice. We have seen the cauldrons but they do not seem to be increasing in size at any dramatic rate, at least not that I have read so far. So at the present time, we might be seeing some minor eruptions of magma under the ice but the hundreds of meters of ice above them are keeping a lid on things so far. To get some idea, imagine an undersea volcanic vent in several hundred meters of water. It generally will not (can not) erupt explosively because the pressure prevents a large amount of steam formation. It is the sudden volume change from liquid to gas that causes the explosive power to blow ice and rock out of the way. Under great pressure, that isn’t likely to happen. And luckily, the caldera is concave shaped which tends to keep the ice and water inside. The worst case scenario is a collapse of the center of the caldera into the magma chamber like pushing a cork into a wine bottle. That would be massive. It is quite possible we could already have seen rather spectacular eruptions inside that caldera were it not for the several hundred meters of ice keeping a lid on things.
A fourth worry is the inflation being seen in other areas. That says magma is still moving around and it could find a path to the surface anywhere at any time. Injection of fresh, hot material into a partially “slushy” old magma chamber could re-animate that system in a hurry. We see magma from the caldera area apparently moving Northeast filling the currently active dike system. This says that resistance in that direction was less than the resistance to going “up”. We might also be seeing some movement to the Northwest. Now it looks like we might be seeing some movement to the Southwest. This worries me because it implies that the break to the current dike was not enough to relieve the pressure and it has continued to find other directions in which to go. The earthquake activity can cause additional fractures to form and allow other pathways to form and completely change the nature of things at any time.
Or the whole thing can just stop. It could stop right now as I am typing this or tomorrow. Nobody knows. The POTENTIAL here is great for a large eruption but that is not to say there is a definite indication that there WILL be a large eruption. The continued deflation of the caldera likely means that material is leaving that area faster than it is entering but we don’t know how much of that collapse of the surface is ice melting and how much is the actual floor of the caldera subsiding. It is likely some combination of both judging from the cauldrons.
The warning sign that would flip my alarm switch is some major change in geothermal activity. If we see steam coming from the cracks in the glacier, existing fumeroles turning into geysers, new fumeroles appearing where none had been before, increased water temperature UPSTREAM from the current lava dam across the river outflow from the glacier, any of those would cause me serious concern as would a rather sudden increase in the number of large quakes in the caldera area.
As I type this I am noting that the rapid inflation at Grimsfjall has reversed and is now deflating. That would imply that magma has found another path someplace and is spreading out somewhere under the surface but that can reverse again at any time.
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