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. Volcanoes like Mount Hood are very episodic in their eruptive behavior, and have periods with frequent eruptions over decades to centuries, separated by dormant periods lasting centuries to thousands of years. The volcano ended a long (~10,000 yr) dormant period about 1,500 years ago and has had two eruptive period of lava-dome growth in the past 1,500 years. A significant eruption of Mount Hood, such as an eruption of lava domes that collapse to form pyroclastic flows and lahars, would displace several thousand residents and cause billion-dollar-scale damage to infrastructure and buildings.
In addition to a large and growing nearby residential population, Mount Hood is a major recreation destination for skiing, climbing, hiking, camping, and other types of tourism. There are also significant elements of transportation and electrical power infrastructure in the area, all of which would be affected by future activity and cause major economic losses in the region.