Scientia Marina, Vol 65, No S1 (2001)

Flank stability and processes off the western Canary Islands: a review from El Hierro and La Palma


https://doi.org/10.3989/scimar.2001.65s121

Roger Urgeles
GRC Geociències Marines, Universitat de Barcelona, Dept. d’Estratigrafia i Paleontologia, Spain

Miquel Canals
GRC Geociències Marines, Universitat de Barcelona, Dept. d’Estratigrafia i Paleontologia, Spain

D. G. Masson
Southampton Oceanography Centre, Challenger Division for Seafloor Processes, United Kingdom

Abstract


The morphological characterisation of the western submarine island flanks of El Hierro and La Palma differentiates four type-zones that may give new insights into the evolution of oceanic island slopes. The different type-zones result from the interplay between constructive volcanic processes, hemipelagic settling and volcano collapses. The latter results in massive debris avalanche deposits, which form large volcaniclastic aprons. In most cases, the headwall scarps are clearly exposed on the emerged part of the islands. The events that occurred in the youngest and westernmost islands of El Hierro and La Palma have vertical runouts exceeding 6,000 m and volumes that can reach several hundred km3. The landslide frequency for the entire Canaries is one major event per 90 ka. Triggering mechanisms are closely related to magmatic processes. The increase in the shear stress is directly linked with the forceful intrusion of magma along ridge-rift systems, while in the western Canary Islands it seems that the main process reducing shear resistance may be related to the rise in pore pressure due to hydrothermal circulation.

Keywords


landslides; debris avalanches; Canary Islands; El Hierro; La Palma

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