There is evidence of at least three major gravitational landslides that have affected El Hierro in the last few hundred thousand years. The most recent of these was the 'El Golfo' landslide that occurred about 15 thousand years ago, involving collapse of the northern flank of the island. The landslide formed the El Golfo valley and created a debris avalanche with a volume of 150-180 km3. Turbidite deposits related to this landslide have been recognized in drill cores from the Agadir Basin to the north of the Canary Islands. Detailed analysis of these deposits suggests that the slope failure did not occur as a single event but a series of smaller failures over a period of hours or days. Local tsunami are likely to have been triggered by these landslides but no evidence has been found to confirm this. Tanganasoga formed near the top of the El Golfo landslide headwall, on the upper part of the north-facing scarp slope.