Massive flank failures and tsunamis in the Canary Islands: Past, present, future

Abstract

Massive flank failures involving tens of km 3 are the most important process in the destruction of volcanic islands. They produce debris avalanches that may generate giant tsunamis when entering the sea, This paper presents a review and a preliminary methodology to assess the hazard of tsunamis induced by massive flank failures in the volcanic islands, applied in the Canary Islands. At least 14 massive flank failures occurred in these islands during the Quaternary. The methodology consists of the following steps: reconstitute the temporal and spatial distribution of the failures; determine the characteristics of the past failures, by comparing the characteristics of the submarine deposits with those of the scars; identify tsunami deposits and correlate them, if possible, with flank failures. Marine conglomerates on the west coast of Gran Canaria are interpreted as tsunami deposits. The Güímar sector collapse, on the east coast of Tenerife (ca. 800 ka) is the closest possible source for this tsunami. Nevertheless, the present-day hazard of massive flank failure and tsunami is very slight in the Canary Islands. The western islands of La Palma and El Hierro, where 65 % of the quaternary failures occurred, do not show any evidence of impending failures. © 2005 Gebrüder Borntraeger.