VUELCO

Further Reading for Mount Teide, Tenerife, Spain

Volcanic deposits

 

View of rocks at TeideThe construction of Teide and Pico Viejo stratovolcanoes derives from the interaction of two different shallow magma systems that have evolved simultaneously, giving rise to a complete series from basalt to phonolite. Thus, both edifices consist dominantly of mafic to intermediate products with volumetrically subordinated felsic products. Nevertheless, the latter predominate in the recent output of the Teide–Pico Viejo stratovolcanoes. Eruptions at both stratovolcanoes have occurred from their central vents but also from a multitude of vents distributed radially around their flanks in three preferential directions: NE, NW, and S. Mafic and phonolitic magmas have been erupted indistinctively from these vents.

 

The recent volcanic history (last 35 ka) of the Teide–Pico Viejo stratovolcanoes and its explosive activity indicates that the number of eruptions occurred during this period is rather important, including strombolian, violent strombolian and sub-plinian magmatic eruptions, as well as phreatomagmatic eruptions of mafic magmas. However, the total volume of magma erupted in this period (1.5–3 km3) is small compared to the total volume of the central complex. Phonolitic magmas represent the 83% of that volume whereas the remainder consists of magmas of mafic compositions. Phonolitic eruptions have been less frequent but much more voluminous than mafic eruptions and their eruption rate is progressively increasing in the period considered.

 

Although the recognized phonolitic eruptions from Teide–Pico basically develop domes and/or lavas flows with a wide range of thicknesses and extensions, in some cases recent field studies have allowed to identify the presence of ignimbrites and block and ash deposits associated with the recent (Holocene) eruptive history of Teide–Pico Viejo. Some of these deposits can be recognised at the northern side of both stratovolcanoes. The presence of these deposits, together with fall products indicates that it is necessary to reconsider the previous assumption that Teide–Pico Viejo are predominantly effusive volcanoes and do not represent a significant threat to their surroundings.

 

All the explosive eruption types that we have been able to distinguish from Teide and Pico Viejo during the last 35,000 years would today cause a serious impact on the infrastructure and economy of the island. Indeed they would probably affect the air traffic, and some of the main energy and water lifelines. Therefore, a hazard assessment programme should be conducted on Tenerife in order to quantify the future potential volcanic risk and to propose mitigation strategies.

 

From the analysis of past activity, it can be seen that even the smallest eruptions that are likely to occur on Tenerife (e.g., Strombolian eruptions from mafic magmas) would generate enough ash to impose a serious threat to the civil aviation, a basic need for the survival of the island. Eruptive activity from the central complex, a possibility that should not be ruled out at all, would however cause a more significant impact. Moreover, the possibility for Teide–Pico Viejo to evolve into a more complex phonolitic system, with a higher explosive potential, should not be discarded. The similarity in the evolution patterns shown by the previous cycles in the construction of the Tenerife central complex and that from Teide–Pico Viejo suggests that the most recent cycle has just started to generate phonolites and that the production of these magmas is likely to increase in the future.

 

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