A European research team, led by a Spanish scientist, shows for the first time how the Teide-Pico Viejo stratovolcano on the Canary Islands was formed and how long it took.

Until now there had been several hypotheses about how the depression in the Las Cañadas caldera was formed, in which the Teide (3,718 metres) and Pico Viejo (3,135 metres) volcanoes rose on the island of Tenerife.

A new study confirms that the caldera was formed as a result of a tectonic movement, and most of the Icod valley filling, which is the base of the stratovolcano, was produced in a period of 40,000 years.

"On a geological scale, this is a very short period of time" Vicente Soler, a researcher at the Volcanological Station of the Canary Islands and coordinator of the study that was published in Geomorphology, said. This new dating was possible because scientists have had underground access to the first lava emitted since the movement for the first time.

The team of scientists collected over a hundred samples to find out when the movement occurred, i.e., 180,000 years ago. According to the results, the system responded 160,000 years ago and the new volcano began to form 120,000 years ago.

The 'hole' in which the Teide arose

The movement caused a 'gap', which is the large depression in the caldera. In the same area of the Canary Island "the Teide volcano grew as a geological response" the researcher stated.

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During recent decades, the geological cause of this depression has sparked scientific controversy. Until now there were two plausible hypothesis of the origin of these depressions, both for the Cañadas del Teide and for the Güimar and Orotava valleys.

The first hypothesis attributes its formation to a sinking after an eruption that emptied the magma chamber, creating the gap in the caldera. After several investigations, the second hypothesis, that a landslide from the north of the island towards the sea was confirmed as the cause of the depression. The area is now surrounded by vertical walls (except for the upper part) which would be the "scar caused by the big movement," Soler confirmed.

As time passed, the big dip was filled and formed the Teide, which became the highest peak in Spain as a result of "nature's fanciful whim," an eruption "that occurred in the 14th century" the geophysicist forecast.

Dating Canary rocks

The study also tells us how long magma, originally basalt rocks, took to evolve into another type of material. "The age of the rocks has been deduced from their potassium and argon content, as the amount of the two chemical elements is proportional to the time elapsed since they cooled" Soler explained.

Since 120,000 years ago, magma has differentiated over time, giving the Teide area its current characteristics. The biggest differentiation is on Montaña Blanca, where there are pumice stones from an eruption that occurred 2000 years ago.

However, there are other rocks that are typical of the area, such as trachyte and phonolite, which stopped being basalt when they lost iron and their silicon dioxide content increased. Soler commented that the geochemical analysis of rocks tells us about the state of the magma system, what point it is at, and how it evolves.