Philippines Volcano Deaths Raise Climbing Questions
A surviving climber is carried on a stretcher by rescuers after the volcano a 20-person group was climbing erupted unexpectedly.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 May 8, 2013
This one was a fun one.
The mayon volcano is being fed via a long deep crustal magma filled fracture extending the bulk of the length of the philippine arc in S. Luzon.
The result has been periodic eruptions throughout the historic timescale.
The "fun" part for the volcanologists is that following a tectonic squeeze (fastest in S.of luzon) that squeezes a pod of magma into the base of the Mayon magma chamber, there is a spectacular eruption followed by a wind down as the inflated crust around the magma chamber subsides and squeezes up a relatively gas poor part of the residual magma in the upper part of the magma chamber. This magma then cools & crystallises in the upper part of the volcano with lots of minor earthquakes and lots of steaming.
This of course gives the usual volcanologic alerts where the volcano is deemed too dangerous to approach.
The deep part of the feeder pipe connected to the magma chamber at depth also cools, this time more slowly and forms a plug which eventually fills the fractures in the plug with low temperature minerals (high temperature hydrothermal minerals) which prevent the steam release from the cooling magma.
At that point the volcano stops steaming and is deemed relatively safe.
Introduce climbers & adventurers @ this point...
The problem in this scenario is that Mayon is fed from a deep long horizontal fracture which continues to be squeezed via tectonic convergence and will eventually splurge another pod of gas rich magma into the base of the magma chamber.
Insert general mountain climber noises somewhere about here...
The magma pod intruded into the base of the volcano is anywhere from 60 to 95 Km deep at the point of arrival & takes a while to exsolve gas & mix with the base of Mayon's near cylindrical thin magma chamber. The gas (mainly steam) finally reaches the feeder pipe for the eruptive activity, and accumulates behind the plug of sealed rock that marks the top of the feeder pipe for the last eruption, now cooled & fractured into large blocks.
More mountain climber noises about here...
The pressure of accumulated steam finally fractures the sealed part of the upper feeder pipe and blows out the upper part as a mix of steam, ash, and large blocks of the former congealed lava; @ that point the climbers & adventurers become local landcape features, and statistic history.
The activity then alters from hydrothermally dominated phreatic to magmatic as the newly intruded into & mixed magma reaches the surface, with increasing heat & gas emission followed by eruption of magmatic gas & lava. This may vary from minor strombolian activity through to sub plinian st vincent style pyro flows & clastogenic lava. The type of activity depends upon the amount of new magma intruded into the base of the magma chamber prior to the new activity. With a large intrusion, the magma erupted is gas rich and basaltic rather than the usual basaltic andesite in composition because its volume overwhelms the volume of the usual retained magma in Mayon's chamber.
Look out in near future for ash & lava from Mayon proper as this particular "pop" marks the start of the next eruptive episode.
Have a nice day: Ag
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