Lahars

Mount Hood is an active volcano close to rapidly growing communities, recreation areas, and major transportation routes and therefore imposes heightened risk.

Lahars can be generated by hot volcanic flows that melt snow and ice or by landslides (debris avalanches) from weakened rock forming the steep upper flanks of the volcano.

Mount Hood, which has been active for at least 500,000 years, occupies a long-lived focus of volcanic activity that has produced ancestral Hood-like volcanoes for the past 1.5 million years.

When Mount Hood erupts again, it will severely affect areas on its flanks as well as locations far downstream in the major river valleys that head on the volcano.

Both eruptive and noneruptive processes at Mount Hood generate several types of landslides and water-mobilized flows that sweep the volcano’s flanks and surge down river valleys.

Glaciers and perennial snowfields on Mount Hood cover about 13.5 square kilometers and contain more than 300 million cubic meters of ice and snow.