It hasn’t been peaceful recently on the holiday islands of the Canaries. Repeated small earth tremors have grown in size with the largest to date being an M4.9 which struck on 31 March 2013, Easter Sunday. What are the possible implications of this series of tremors for the volcanic island of El Hierro?
El Hierro Volcano and the Canary Islands
Most volcanoes are associated with the boundaries of the Earth’s tectonic plates – either at subduction zones, where the earth’s tectonic plates collide and one is subducted beneath the other, subjecting rocks to immense pressures and temperatures which cause them to melt, or at rift zones where the plates move apart and molten rock rises through the stretched crust.
But what about volcanoes such as those in the Canaries (or Hawaii) which occur at a distance from such boundaries? Sometimes a plume (or hot spot) of molten rock rises to the surface from within the Earth’s core and volcanoes occur at the surface. Although there is some discussion as to the origins of the Canaries, it is distinctly possible that they may be the result of hotspot volcanism.
El Hierro: Past Volcanic Eruptions
Whatever their origin, the Canaries are unquestionably volcanic – and, as a result of that volcanic activity, still evolving. The islands’ listing in the Smithsonian Institute’s Global Volcanism Program includes six volcanoes, although not all are currently active. Although the listing gives the most recent major eruption as 1971, and the last known for El Hierro as over 2,000 years ago, the latter has in fact been more recently active.
Looking more closely at the GVP’s records for Hierro shows that the volcano may have erupted three times since then, in 1677, 1692 and 1793. After that, things remained quiet until the organisation’s monthly reports indicate eruptive activity in 2011; the website Volcano Observatory also indicates eruptive activity in the 2012.Decoded Science
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