Mount Hood is currently hit by a swarm of small earthquakes. As of now, about 29 quakes hit the active stratovolcano in the Cascade Volcanic Arc.
The largest quake was a M2.8 and hit on October 17, 2021 at 7:42PDT (October 18, 2021 at 2:42am UTC).
The tremors hit at a depth between 0.25 miles (0.4 km) and 1.99 miles (3.2 km), with most of the tremors (23) occuring between 1.30 miles (2.1km) and 1.68 miles (2.7 km). Most of the earthquakes occurred about 15 hours ago, but the swarm is continuing! The seismic activity was low during the last 30 days and picked up about 16 hours ago. There is clearly something going on at Mount Hood right now!
Future eruptions at Mount Hood, Oregon
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.
Much of the Mount Hood edifice is formed of lava flows, but eruptive activity during the past 30,000 years has been dominated by growth and collapse of near-summit lava domes to produce broad fans of pyroclastic flow deposits.
Similar deposits were probably formed in Mount Hood’s past but were largely eroded, especially during ice ages, and are poorly represented in the geologic record.
The last two periods of eruptive activity occurred about 1,500 years ago and in the late 18th century.
In addition to Mount Hood, other volcanoes scattered through the nearby area have erupted during the past 500,000 years. In contrast to the long-lived activity at Hood, each of these regional volcanoes was active for a relatively short period of time. The youngest such volcano is the 7-km-long Parkdale lava flow whose vent lies about 12 km north-northeast of the summit of Mount Hood.
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.
By the way, a new study suggests that the magma sitting 4-5 kilometers beneath the surface of Oregon’s Mount Hood has been stored in near-solid conditions for thousands of years, but that the time it takes to liquefy and potentially erupt is surprisingly short – perhaps as little as a couple of months. So be prepared for the next blast! [PNSN, Volcano Discovery, Oregon State University, USGS]