Could Gentle Caribbean Unleash a Devastating Tsunami?
The Caribbean usually conjures images of white sandy beaches and sparkling turquoise water, but beneath the sea's tranquil surface, powerful forces are at work.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 May 21, 2014
This one ported over by me from another thread on the same subject.
This one probably more informative than the news article @ the thread header.
Of note here is that the last major megathrust earthquake & tsunami here was approx 500Bp & was either immediately before, or immediately after the arrival of Columbus (1486 was issued as one date). The event affected the S. American& Caribbean plates & the S.Antilles backarc basin with relaxation of the crust on a SE vector and a tsunami (mapped) radiating through the S.Caribbean on a NW vector.
The area affected appears to run from N. of Martinique to S. of Grenada with Kick em jenny almost in the middle of the region affected. Magma filling fractures in the base of the relaxed crust from the base crustal magma discs has been squeezed into the volcanoes since the event. It is likely in fact that Kick em Jenny actually dates from that quake & has been the main active vent of the Grenadines volcano (a line of submarine & subaerial cones NNE. of Grenada) ever since.
Collapse of the volcano if it occurs will be relatively shallow skinned & will likely produce a local tsunami, big @ source & rel;atively small @ distance similar to the collapse of Ritter island in the Schouten islands which was a rather bigger volcano. The magma is basaltic andesite & being relatively new it will not produce a Krakatau type event anytime soon.
Of real interest is that the descending plate is rather busy with volume change earthquakes in the S. sector of the Antilles arc.
The N. sector of the Antilles arc by contrast is rather less busy with regards to the descending plate as a result of the last megathrust event there being ~1500Bp & rather bigger than the 500Bp event. That one was a result of crustal relaxation of the Antilles backarc basin over the descending N.American plate (the usual culprit) with an E. vector & a tsunami radiating W. across the Caribbean from the arc. There is still magma squeezing into the volcanoes on the N. & central part of the Antilles arc (will affect volcanoes all the way from Saba through to St. Vincent), with the last being the rather notable event chain @ Montserrat.
With the volcanoes still busy in the north & the descending N.American plate still descending, the next megathrust event there is still a while away but it will be big & will be very nasty.
A number of science papers have dealt with teletsunami from Antilles arc megathrust events on the Netherlands antilles N. of venezuela, but very few have documented palaeotsunami on the antilles arc islands themselves. It appears that on these islands the tsunami are erosive removing the pre existing palaeosols produced during the recompression interval time.
key word for a google search is [ palaeo tsunami "bonaire" ] which should fill in all the gaps.
Of more note is that the E.side of Hispaniola is also subducting the N.American plate & will also undergo a crustal relaxation megathrust event, probably during Antilles arc events vs. the N.American plate. which will make things interesting for Florida in particular. No megathrust palaeotsunami have been found here either (probably due to scour as in the Antilles arc due to the large tsunami size & steep slopes.
Have a nice day: Ag
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