Magnetotelluric study of the Teide (Tenerife) and Timanfaya (Tanzarote) volcanic areas

The application of a magnetotelluric surveying method, developed specifically for detection of strong conductivity contrasts, has permitted interpretations of the deep structure of two important volcanic formations in the Canary Archipelago: the Timanfaya (Lanzarote) and Teide (Tenerife) volcanoes. Beneath the Timanfaya volcano, a highly conductive body (p ≤ 1 Ω m) has been detected, which is interpreted as a shallow magma chamber associated with the eruption which took place between the years 1730 and 1736. The core of this intrusion, still largely molten, would be located at approximately 4 km depth and would still maintain temperatures in excess of 900 °C.In the Telde caldera the asymmetry of the apparent resistivity components indicates a double depression; furthermore, a highly conductive level encountered in the centre of the eastern part of the volcanic complex has been attributed to the persistance of relatively high temperatures in the root of the last salic dome, extruded inside the caldera. In both zones, the deep limiting horizon is a highly conductive layer corresponding to the mantle (15 km in Lanzarote and 13 km in Tenerife), whereas other, more superficial, discontinuities have been related to local structures.