remain. Tephra The largest threat from volcanoes in the Garibaldi chain would likely be due to tephra released during explosive eruptions. Mount Meager massif in particular poses a major long-distance threat to communities throughout southern British Columbia and Alberta because of its explosive history. It is estimated that over 200 eruptions have occurred throughout the entire Cascade Volcanic Arc in the past 12,000 years, many of them in the United States. Many eruptions in the western United States have sent large amounts of tephra in southern British Columbia. However, all major cities in southwestern British Columbia with populations more than 100,000 are located west of the Garibaldi Volcanic Belt and prevailing winds travel eastwards. Therefore, these communities are less likely to have large amounts of tephra. In the Lower Mainland, a thick layer of volcanic ash can deposit once every 10,000 years and once every 1,000 years. More minor amounts of volcanic ash can be expected more commonly. During Mount St. Helens' eruption in 1980, of tephra was deposited from southeastern British Columbia to Manitoba. Even though all major cities in southwestern British Columbia are located west of the Garibaldi chain, future eruptions from Mount Garibaldi are expected to have significant impacts on the adjacent townships of Squamish and Whistler. An eruption column released during Peléan activity would discharge large amounts of tephra that would endanger aircraft. Tephra may also melt the large sheets of glacial ice east of Garibaldi and cause floods. This could later endanger water supplies from Pitt Lake and fisheries on the Pitt River. An explosive eruption and the associated tephra may also create temporary or longer-term water supply difficulties for Vancouver and most of southern British Columbia. The water reservoir for the Greater Vancouver drainage area is south of Mount Garibaldi. Landslides and lahars Several landslides and lahars have occurred throughout the Garibaldi Belt. At the Mount Meager massif, considerable landslides have occurred from Pylon Peak and Devastator Peak in the past 10,000 years that have reached more than downstream in the Lillooet River valley. At least two significant landslides from the southern flank of Pylon Peak 8,700 and 4,400 years ago dumped volcanic debris into the adjacent valley of Meager Creek. More recently, a large landslide from Devastation Glacier buried and killed a group of four geologists on July 22, 1975. The estimated volume of this landslide is . A considerable landslide as large