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Costa, Roberto

Nom
Costa, Roberto
Affiliation principale
Email
roberto.costa@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/149

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  • Publication
    Accès libre
    Multiple caldera collapses inferred from the shallow electrical resistivity signature of the Las Cañadas caldera, Tenerife, Canary Islands
    (2008)
    Coppo, Nicolas
    ;
    Schnegg, Pierre-André
    ;
    Heise, Wiebke
    ;
    Falco, Pierik
    ;
    Costa, Roberto 
    The Las Cañadas caldera of Tenerife (LCC) is a well exposed caldera depression filled with pyroclastic deposits and lava flows from the active Teide–Pico Viejo complex (TPVC). The caldera's origin is controversial as both the formation by huge lateral flank collapse(s) and multiple vertical collapses have been proposed. Although vertical collapses may have facilitated lateral slope failures and thus jointly contribute to the exposed morphology, their joint contribution has not been clearly demonstrated. Using results from 185 audiomagnetotelluric (AMT) soundings carried out between 2004 and 2006 inside the LCC, our study provides consistent geophysical constraints in favour of multiple vertical caldera collapse. One-dimensional modelling reveals a conductive layer at shallow depth (30–1000 m), presumably resulting from hydrothermal alteration and weathering, underlying the infilling resistive top layer. We present the resistivity distribution of both layers (resistivity images), the topography of the conductive layer across the LCC, as well as a cross-section in order to highlight the caldera's evolution, including the distribution of earlier volcanic edifices. The AMT phase anisotropy reveals the structural and radial characteristics of the LCC.
  • Publication
    Accès libre
    Structural pattern of the western Las Cañadas caldera (Tenerife, Canary Islands) revealed by audiomagnetotellurics
    (2008)
    Coppo, Nicolas
    ;
    Schnegg, Pierre-André
    ;
    Falco, Pierik
    ;
    Costa, Roberto 
    ;
    Burkhard, Martin
    The local and regional structural pattern of volcanic edifices strongly controls the space distribution of electrical resistivity. Here we report on the structural context of the western part of the Las Cañadas caldera of Tenerife (LCC) thought to have initiated the formation of the caldera. Using a new dataset of 11 audiomagnetotelluric tensors we emphasize the resistivity distribution of Ucanca caldera and propose a major revision of its extension. We find that Ucanca caldera has a limited westwards extent and that El Cedro sector is a depression margin of the caldera. According to the extent of hydrothermalized rocks at the base of the LCC wall and the distribution of Pico Teide – Pico Viejo vents, we constrain the location and size of Ucanca caldera. The interpretation of these results also constrains the extension of the Icod Valley and proposes a headwall located below the Pico Teide – Pico Viejo Complex.