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Wednesday, 25 February 2015

Volcano cross-section


The island of La Gomera is essentially a single very large volcanic peak which has had a complex history of eruptions.  There have not been so many huge catastrophic events here as on other islands, so there are no large calderas (as there are on Gran Canaria, for example.) 

The above photo shows part of the cliff above the beach of La Playa, Valle Gran Rey, more or less at the western tip of the island.  At the base of the cliff there are assorted basalts, grey ashes and ignimbrites, then above those we see a series of ash beds -- some of them grey but others red and buff in colour.  These beds have been disturbed / consumed by several intrusions, and we can see the basalt dykes pushed right through them, causing major disruptions in the bedding.  On the right we can see some of the huge rockfalls from slope collapses as the cliff has been eaten away by the sea.

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