The Garibaldi Volcanic Belt in southwestern British Columbia is the northern extension of the Cascade Volcanic Arc in the United States and contains the most explosive young volcanoes in Canada . Like the rest of the arc , it has its origins in the Cascadia subduction zone . Volcanoes of the Garibaldi Volcanic Belt have been sporadically active over a time span of several millions of years . The northernmost member , the Mount Meager massif , was responsible for a major catastrophic eruption that occurred about 2,350 years ago . This eruption may have been close in size to that of the 1980 eruption of Mount St. Helens . Ash from this eruption can be traced eastward to western Alberta . It is also the most unstable volcanic massive in Canada , which has dumped clay and rock several meters deep into the Pemberton Valley at least three times during the past 7,300 years . Hot springs near the Mount Cayley and Mount Meager massifs suggest that magmatic heat is still present . The long history of volcanism in the region , coupled with continued subduction off the coast , suggests that volcanism has not yet ended in the Garibaldi Volcanic Belt . A few isolated volcanic centers northwest of the Mount Meager massif such as the Franklin Glacier Complex and the Silverthrone Caldera , which lie in the Pemberton Volcanic Belt , may also be the product of Cascadia subduction , but geologic investigations have been very limited in this remote region . About 5 – 7 million years ago , the northern end of the Juan de Fuca Plate broke off along the Nootka Fault to form the Explorer Plate , and there is no definitive consensus among geologists on the relation of the volcanoes north of that fault to the rest of the Cascade Arc . However , the Pemberton Volcanic Belt is usually merged with the Garibaldi Volcanic Belt , making Mount Silverthrone the northernmost , but an uncertain Cascadia subduction-related volcano
1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
Geology of the Pacific Northwest