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Lava Flow Hazards at Mount Adams

Lava flows are the most likely type of future eruptive event, but they do not pose as much of a hazard as landslides or lahars because they move slowly (a person can out run a lava flow) with relatively predictable flow pathways. The most recent lava flows extended 7 to 12 km (4 to 7 mi) from the summit to the base of the volcano. They typically travel less than 20 km (12 mi) from vents, but in rare cases during Mount Adams history more voluminous flows reached lengths of 25 to almost 50 km (15 to 30 mi). The annual probability of lava flows affecting one of the small communities south of Mount Adams is very low and estimated to be 0.001 to 0.0001 percent. Communities at risk from lava flows would depend on their proximity to the erupting vent. A lava flow originating on any side of the volcano may impact the road system encircling Mount Adams.