The best known and most documented eruption of the Mount Meager massif is a large explosive eruption that occurred about 2,400 years ago. This eruption, which likely reached 5 on the Volcanic Explosivity Index (VEI), was similar to the 1980 eruption of Mount St. Helens. It sent a massive Plinian column at least high into the atmosphere. Prevailing westerly winds carried volcanic ash from this explosion eastwards to as far as Alberta. Nearby areas were devastated by heavy pyroclastic fall when parts of the Plinian column collapsed. Later, a series of pyroclastic flows were erupted and travelled downstream. After this, a lava flow was erupted that repeatedly collapsed on the steep slopes of Plinth Peak, creating a thick, welded breccia deposit that blocked the Lillooet River. This created a lake just upstream which later collapsed to produce a massive outburst flood. Large boulders were carried downstream for more than , but the destructive floodwaters continued further. Later, a small dacite lava flow was erupted, which cooled into well-preserved columnar joints. The entire eruption cycle originated from the Bridge River Vent on the northeastern flank of Plinth Peak. This is the latest known eruption of the Mount Meager massif, as well as the largest known Holocene explosive eruption in Canada. However, it is unknown when this eruption ended.