Mass wasting in the Western Galapagos Islands

Oceanic island volcanoes such as those comprising the Hawaiian, Canary and Galapagos Islands are known to become unstable with the passage of time, resulting in failures of the subaerial and submarine portion of the volcanic edifices. These mass wasting events appear to be the primary source of destruction and loss of volume of many oceanic islands, but our knowledge of mass wasting in seamount and island chains is still rudimentary. To better understand mass wasting in the western Galapagos Islands, multi-beam bathymetry, backscatter and sidescan sonar data were used to examine topography characteristic of mass wasting. Observations show that mass wasting plays an important role in the morphological development of Galapagos volcanoes. While volcanic activity continues to modify the submarine terrain, the data show that several types of mass wasting can be found in this archipelago. The steep upper slopes of the north and west flanks of Fernandina Island and the north and southwest flanks of Isabela Island are characterized by slump sheets. The lower slopes on the north and west flank of Fernandina and the southwest tip of Isabela Island are characterized by debris flows. The northwest tip of Isabela Island is characterized by chaotic slumping and detached blocks originating from the sector collapse of Volcan Ecuador. Unlike the giant landslides documented by GLORIA imagery around the Hawaiian Islands, the western Galapagos Islands appear to be characterized by small slumps and debris flows. Nevertheless, this study indicates that submarine mass wasting is widespread in the western Galapagos Islands and is an important component of erosion of these volcanic edifices.