A. Hansen

Eruptive and structural history of Teide Volcano and rift zones of Tenerife, Canary Islands

The Teide and Pico Viejo stratocones and the Northwest and Northeast Rifts are products of the latest eruptive phase of the island of Tenerife, initiated with the lateral collapse of its northern flank that formed the Las Canadas Caldera and the Icod–La Guancha Valley ca. 200 ka. The eruptive and structural evolution of this volcanic complex has been reconstructed after detailed geological mapping and radioisotopic dating of the significant eruptive events. A set of 54 new 14 C and K/Ar ages provides precise age control of the recent eruptive history of Tenerife, particularly Teide Volcano, the third-highest volcanic feature on Earth (3718 m above sea level, >7 km high), and unique in terms of its intraplate setting. The development of the Teide–Pico Viejo Volcanoes may be related to the activity of the Northwest and Northeast Rifts. Volcanic and intrusive activity along both rift zones may have played an important role in activating the gravitational landslide and in the subsequent growth, nested within the collapse embayment, of an increasingly higher central volcano with progressively differentiated magmas. The coeval growth of the central volcano with sustained activity along the rifts led to a clear bimodal distribution in composition of eruptive products, with the basaltic eruptions in the distal part of the rifts and phonolitic and more explosive eruptions in the central area, where the differentiated stratocones developed. Current volcanic hazard in Tenerife is considered to be moderate, because eruptive frequency is low, explosivity is modest, and the eruptive activity of the Teide stratocone seems to have declined over the past 30 k.y., with only one eruption in this period (1150 yr B.P.).

Reply to Comment on “Recent unrest at Canary Islands' Teide Volcano?”

Small-magnitude seismic episodes unrelated to a volcanic eruption have been a relatively frequent feature in all the Canaries without causing any significant public alarm. Conversely, great alarm was raised in May 2004 in Tenerife, when apparently numerous low-magnitude seismic signals were recorded, although only a few of them were actually felt in nearby villages. Public alarm was raised by (1) the publication on a Web site of imperceptible seismic signals as low as 0.6 on the Richter scale, most of which were not even adequately localized and yet were reproduced almost daily in the local and national press without further comment or explanation; (2) a Spanish national scientific committee being replaced by a local committee that was scientifically advised by a private company; and (3) publicity given by the media to the prediction made by members of the local committee of a potentially large scale explosive eruption in October 2004 (dubbed “the October volcano” by residents). Interestingly, obvious fumarole activity was absent in autumn 2004 during an inspection of Teide summit by three of us.