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Cumbre Vieja and the San Juan eruption of 1949 (an historical view of the volcano thing)
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Original Message
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Interesting. Read this, and you'll be like the old wise man in the science fiction movies educating the huddled masses about what just happened to them after it's over.
Cumbre Vieja and the San Juan eruption of 1949
Héctor Sacristán / 2 hours ago
The volcano Cumbre Vieja in the island of La Palma has been showing signs of unrest. The question on everyone’s mind is, will there be an eruption? Maybe, or maybe not. This is always hard to know.
The Spanish National Geographic Institute reports inflation, a total of 10 cm of deformation. As such it is evident that there is magma on the move under Cumbre Vieja, it has intruded underneath the volcano.
[link to www.ign.es (secure)]
There have been multiple swarms of earthquakes since 2017 in Cumbre Vieja, a total of nine. Previous swarms were probably magma intrusions too, but which did not reach the surface. The recent swarm however is more shallow and more intense than its predecessors which raises the possibility that the outcome may be different.
The current swarm started on September 12. A total of 4530 earthquakes have been detected at depths of mainly around 10 km, although there are a few which have been very shallow. The swarm commenced under the summit of Cumbre Vieja, where a magma conduit probably exists which is supplying the intrusion. Earthquakes have propagated to the northwest.
This probably represents the propagation of magma filled fractures, possibly sills, radially from the centre of Cumbre Vieja. However the earthquakes only show a but a blur of what is going on down there. The exact shape and pathways used by the intrusions cannot really be known with much precision. It is somewhat similar to the prelude to the eruption of El Hierro in 2011 which also seems to have commenced with a sill that later propagated a crack towards the seafloor.
lots more
[link to www.volcanocafe.org (secure)]
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