Like many other volcanoes in the Garibaldi Volcanic Belt, Mount Cayley has been the source for several large landslides. To date, most geological studies of the Mount Cayley field have focused on landslide hazards along with geothermal potential. A major debris avalanche about 4,800 years ago dumped of volcanic material into the adjacent Squamish valley. This blocked the Squamish River for a long period of time. Evans (1990) has indicated that a number of landslides and debris flows at Mount Cayley in the last 10,000 years might have been caused by volcanic activity. Since the large debris avalanche 4,800 years ago, a number of more minor landslides have occurred at it, including one 1,100 years ago and another event 500 years ago. Both landslides ultimately blocked the Squamish River and created lakes upstream that lasted for a limited amount of time. In 1968 and 1983, a series of landslides took place that caused considerable damage to logging roads and forest stands, but did not result in any casualties. Future landslides from Mount Cayley and potential damming of the Squamish River are significant geological hazards to the general public, as well as to the economic development in the Squamish valley.