Mount Hood is an active volcano close to rapidly growing
communities, recreation areas, and major transportation routes
and therefore imposes heightened risk. Potential hazards include
collapse of growing lava domes and generation of pyroclastic
flows, which in turn melt snow and ice to form lahars that flow
far down valleys; the long-term adjustment of river channels to
the large quantities of volcanogenic sediment dumped into
valleys that head on the volcano; and landslides of
hydrothermally altered material from steep upper slopes of the
volcano that spawn debris avalanches and related lahars. The
most likely widespread and hazardous consequence of a future
eruption would be for lahars to sweep down the entire length of
the Sandy and White River valleys. Modest production of tephra
would also pose chiefly non-life-threatening hazards to nearby
communities. Future eruptions of Mount Hood could seriously
disrupt transportation (air, river, and highway) and
hydroelectric power generation and transmission in n