Mount Hood volcano, Oregon's highest peak, forms a prominent backdrop to the state's largest city, Portland, and contributes valuable water, scenic, and recreational resources that help sustain the agricultural and tourist segments of the economies of surrounding cities and counties.


Mount Hood has erupted episodically for about 500,000 years and hosted two major eruptive periods during the past 1,500 years. During both recent eruptive periods, growing lava domes high on the southwest flank collapsed repeatedly to form pyroclastic flows and lahars that were distributed primarily to the south and west along the Sandy River and its tributaries. The last eruptive period began in AD 1781 and affected the White River as well as Sandy River valleys. The Lewis and Clark Expedition explored the mouth of the Sandy River in 1805 and 1806 and described a river much different from today's Sandy. At that time the river was choked with sediment generated by erosion of the deposits from the eruption, which had stopped about a decade before their visit. In the mid-1800's, local residents reported minor explosive activity, but since that time the volcano has been quiet.


Date published: June 11, 2021

Mount Hood's June 5, 2021 Earthquake

Normal faulting? No change in volcanic hazard? Cascades Volcano Observatory geophysicists describe how they interpret earthquake data using the June 5, 2021 Magnitude 3.9 earthquake at Mount Hood as an example.

Date published: June 5, 2021

M3.9 earthquake and swarm occur at Mount Hood on June 5, 2021

The M 3.9 earthquake occurred at a depth of 2.7 miles below sea level. At this time, seismologists do not believe the earthquake swarm signifies a change in volcanic hazard at Mount Hood, and will continue to monitor the swarm and issue updates as the situation warrants.

Date published: March 2, 2021

Short-lived burst of earthquakes occur at Mount Hood, March 1, 2021

Burst-like swarms commonly interpreted to be caused by movement of hydrothermal fluids (water).

Find a U.S. Volcano