The Bridge River Vent is a volcanic crater in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada.

The vent rises above the western shoulder of the Pemberton Valley and represents the northernmost volcanic feature of the Mount Meager massif.

The interface between the Juan de Fuca and North American plates remains locked for periods of roughly 500 years.

[3] The Bridge River Vent was formed during an onset of eruptive activity about 2,350 years ago that ended a long period of dormancy at the Mount Meager massif.

[2][5] They are exposed in cliff sections near the 209 km (130 mi) long Lillooet River and comprise the Pebble Creek Formation.

[2] At the start of the eruption, a large Plinian column rose above the Bridge River Vent, creating its bowl-shaped volcanic crater.

This explosive eruption might have been followed by the collapse of a former lava dome based on the existence of a thick cover of welded vitrophyric breccia.

Another grain, consisting of extremely rounded but glacially dissected quartz monzonite, is another small but widespread element of the pyroclastic fall deposit.

[2] Strong high-altitude winds carried material east-northeasterly from the Plinian column to as far as Alberta, 530 km (330 mi) away from the vent to produce a large volcanic ash deposit.

These features might represent the first evidence of water reaction during the eruption and are mainly located near the 23 m (75 ft) high Keyhole Falls along the Lillooet River.

Fine-grained volcanic ash, crystal and rock fragments comprise the matrix of the second major pyroclastic flow deposit.

[2] A second hot welded block and ash flow erupted off the face of an advancing lava dome into the Lillooet River valley, forming a pyroclastic dam at least 100 m (330 ft) high.

Infrequent welded breccia grains in the thickest portion of the block and ash flow deposit adjacent to Keyhole Falls include grey spherulites and lithophysae.

Large volcanic blocks derived from the pyroclastic dam were carried downstream for 3.5 km (2.2 mi) where they were deposited in the water-saturated debris.

The flood was significant enough to leave volcanic blocks 30 m (98 ft) above the pre-existing valley floor 5.5 km (3.4 mi) downstream of the dam failure.

Apparent absence of biotite and occurrence well to the south of the Bridge River Ash likewise favour a separate identity.