The Cascade Volcano Observatory’s instruments (CVO) detected an increased rate of local ground deformation in the Three Sisters volcano group located in the central part of the Oregon Cascade Range.
The significant change of the vertical deformation rate has been measured in the 20-km diameter area centered about 5 km west of the South Sister volcano. According to satellite radar images, the ground has been uplifted by 2.2 cm between June 2020 and August 2021 and continues to inflate to the present.
Phases of elevated uplifts have been observed in this volcanic area before and this is likely reflecting magma intrusion and migration under the surface, supported also by continued deformation of the surface. The elevated inflation appears to be a continuing period probably linked to accumulating magma in the shallow magma chamber (7 km).
During 1995 and 2020, the area has been uplifted by 30 centimeters.
A series of small earthquake swarms occurred in October 2021, December 2021 and January 2022. Most of shallow quakes were too weak to locate.
The alert level for the volcanoes remains at Level 1, which is no sign of an impending eruption.
Volcanic activity occurred frequently from various vents during the past 10,000 years, last about 1,600 years ago.
Source: Cascade Volcano Observatory volcano activity update 31 January 2022