Geothermal and Seismic Activity
At least four volcanoes have had seismic activity since 1985, including Mount Garibaldi (three events), Mount Cayley (four events), Mount Meager (seventeen events) and the Silverthrone Caldera (two events). Seismic data suggest that these volcanoes still contain active magma chambers, indicating that some Garibaldi Belt volcanoes are likely active, with significant potential hazards. The seismic activity corresponds with some of Canada's recently formed volcanoes and with persistent volcanoes that have had major explosive activity throughout their history, such as Mount Garibaldi, Mount Cayley and Mount Meager.
A series of hot springs adjacent to the Lillooet River valley, such as the Harrison, Sloquet, Clear Creek and Skookumchuck springs, are not known to occur near areas with recent volcanic activity. Instead, many are located close to 16-26 million year old intrusions that are interpreted to be the roots of heavily eroded volcanoes. These volcanoes formed part of the Cascade Volcanic Arc during the Miocene period and their intrusive roots extend from the Fraser Valley in the south to Salal Creek in the north. The relationship of these hot springs to the Garibaldi Belt is not clear. However, a few hot springs are known to exist in areas that have experienced relatively recent volcanic activity. About five hot springs exist in valleys near Mount Cayley and two small groups of hot springs are present at Mount Meager. The springs at Meager might be evidence of a shallow magma chamber beneath the surface. No hot springs are known to exist at Mount Garibaldi like those found at Mount Meager and Mount Cayley, although there is evidence of abnormal high heat flow at the adjacent Table Meadows and other locations. Abnormal warm water adjacent to Britannia Beach could be geothermal activity linked to the Watts Point volcanic zone.