Submarine landslides around the Canary Islands

The morphology and structure of the submarine flanks of the Canary Islands were mapped using the GLORIA long-range side-scan sonar system, bathymetric multibeam systems, and sediment echosounders. Twelve young (<2 Ma) giant l andslides have been identified on the submarine flanks of the Canary Island s up to now. Older landslide events are long buried under a thick sediment cover due to high sedimentation rates around the Canary Islands. Most slide s were found on the flanks of the youngest and most active islands of La Pa lma, El Hierro, and Tenerife, but young giant landslides were also identifi ed on the flanks of the older( 15-20 Ma) but still active eastern islands. Large-scale mass wasting is an important process during all periods of majo r magmatic activity. The long-lived volcanic constructive history of the is lands of the Canary Archipelago is balanced by a correspondingly long histo ry of destruction, resulting in a higher landslide frequency for the Canary Islands compared to the Hawaiian Islands, where giant landslides only occu r late in the period of active shield growth. The lower stability of the fl anks of the Canaries is probably due to the much steeper slopes of the isla nds, a result of the abundance of highly evolved intrusive and extrusive ro cks. Another reason for the enhanced slope instability is the abundance of pyroclastic deposits on Canary Islands resulting from frequent explosive er uptions due to the elevated volatile contents in the highly alkalic magmas. Dike-induced rifting is most likely the main trigger mechanism for destabi lization of the flanks. Flank collapses are a major geological hazard for t he Canary Islands due to the sector collapses themselves as well as trigger ing of tsunamis. In at feast one case, a giant lateral blast occurred when an active magmatic or hydrothermal system became unroofed during flank coll apse.