Big Bangs and Catastrophism on Tenerife

Last week I was fortunate enough to join my fellow Geology students in travelling to Tenerife (pronounced Ten-err-iff-AY apparantly) where we were to spend the week investigating the different deposits all over the western two thirds of the island. The reason for this trip was simple, we as Geologists had up until this point seen very little of effusive (above surface) volcanism and the deposits that they produced and although some of the students had done their independent mapping projects in areas of effusive volcanism, little instruction had been given.

Las Cañadas 'Caldera' - Photo Courtesy of Rachel Garnett

Caldera wall & rim, Montaña Blanca and A'a Lava flows (brown tongues) can all be seen in this image, as well as the 2ka Fissure Eruption fissure - trending to top right.

There is a large feature in the centre of Tenerife, which is known as the Las Cañadas caldera (word of latin origin, meaning a “cooking pot”) and despite there being two opposing models for the formation of this feature, over the course of the week, indeed in the weeks of lectures before the trip, it became apparant that none of the lecturers and demonstrators were particularly fond of one of the models that attempt to explain the formation of the “Caldera”.

The two models concerned are the Volcanological Caldera Collapse model, whereby beneath the present day caldera structure there was once a large magma chamber; with approximately the same footprint as the caldera, which evacuated explosively, then subsided creating the caldera structure seen today – this was the favoured model. The other model is the Sector Collapse model, which contends that somewhere beneath the palaeo-surface of the volcanic edifice (before the modern Mt Teide/Pico Viejo volcano formed) magma became trapped, only to be released later after a massive landslide (known as a Sector Collapse) took out most of the material capping the trapped magma, allowing the formation of the Mt Teide/Pico Viejo edifice. You may remember this model from the days when the newspapers said that half of La Palma (another Canary Island) was due to collapse into the sea and swamp the east coast of the USA!

Strangely, whilst there is good evidence for both Sector Collapse and Caldera Collapse having a part to play in the formation of the caldera, the Sector Collapse proponents seem to adamantly state that no volcanism of any kind had any part to play in the formation of Las Cañadas caldera, whilst the Volcanologists are willing to accept a more reasoned approach whereby both models are considered to have a role. Indeed I suspect it is the sheer adamant attitude of the Sector Collapse proponents is what is preventing the volcanologists from taking them 100% seriously.

There are also some compelling questions for both sides to answer, for the volcanologists need to be able to explain the existence of what are interpreted as sector collapse deposits to the north whereas the sector collapse people need to explain the existence of La Forteleza scarp to the north side of the caldera. As with a lot of the finer details of science, the more you learn, the more controversies you uncover and the fewer certainties you find.

Perhaps it would be good to get a really good, structured debate and discourse going between the two parties…. it may at least be interesting from an academic perspective.

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