The Mount Meager massif is the most voluminous composite volcano in the Garibaldi chain and British Columbia , as well as the most recent to erupt . It has a volume of and consists of an eroded stratovolcano , ranging in composition from andesite to rhyodacite . Several dissected lava domes and volcanic plugs are present on its glaciated summit , as well as a clearly defined volcanic crater with a lava dome placed within it . At least eight volcanic vents compose the complex and have been the sources for volcanic activity throughout massif 's 2.2 million year history . A well-documented history of volcanism is present at the Mount Meager massif , with its most recent eruption about 2,350 years ago that was similar in character to the 1980 eruption of Mount St. Helens and the continuous eruption of Soufrière Hills on the island of Montserrat . This is the largest recorded Holocene explosive eruption in Canada , originating from a volcanic vent on the northeastern flank of Plinth Peak . It was Plinian in nature , sending an eruption column at least high into the stratosphere . As prevailing winds carried ash of the column eastwards , it deposited across British Columbia and Alberta . Subsequent pyroclastic flows were sent down the flanks of Plinth Peak for and were later succeeded by the eruption of a lava flow that demolished many times . This created thick agglutinated rubble that successfully blocked the adjacent Lillooet River to form a lake . Subsequently , the breccia dam collapsed to produce a catastrophic flood that deposited house-sized boulders more than downstream . After the flood took place , a small dacite lava flow was erupted that later solidified to form a series of well-preserved columnar joints . This is the last phase of the 2350 BP eruption , and subsequent stream erosion has cut though this lava flow to form a waterfall
1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
Garibaldi Volcanic Belt