Temporary Global Positioning Systems (GPS) stations are deployed to determine if uplift continues in the Three Sisters area. Since surface changes were discovered in 2001, the rate of uplift has decreased to less than 1.0 cm (0.4 in.) per year.
Multimedia
Images
Temporary GPS stations recording area deformation at Three Sisters, OR
Temporary Global Positioning Systems (GPS) stations are deployed to determine if uplift continues in the Three Sisters area. Since surface changes were discovered in 2001, the rate of uplift has decreased to less than 1.0 cm (0.4 in.) per year.
Three Sisters, OR simplified hazards map
Three Sisters, Oregon simplified hazards map showing potential impact area for ground-based hazards during a volcanic event.
Three Sisters, Oregon simplified hazards map showing potential impact area for ground-based hazards during a volcanic event.
Southeastward view across saddle between North and Middle Sisters. ...
In left foreground, ice-ravaged mafic edifice Little Brother is separated from North Sister by Little Ice Age trough of Collier Glacier. Both North Sister and Little Brother expose numerous oxidized scoria falls, whereas smooth black Middle Sister cone is cloaked by mafic lava flows.
In left foreground, ice-ravaged mafic edifice Little Brother is separated from North Sister by Little Ice Age trough of Collier Glacier. Both North Sister and Little Brother expose numerous oxidized scoria falls, whereas smooth black Middle Sister cone is cloaked by mafic lava flows.
Map showing one-year probability of accumulation of 1 centimeter
Map showing one-year probability of accumulation of 1 centimeter (0.4 inch) or more of tephra from eruptions of volcanoes in the Cascade Range.
Map showing one-year probability of accumulation of 1 centimeter (0.4 inch) or more of tephra from eruptions of volcanoes in the Cascade Range.
Middle Sister volcano's east face with shingled stacks of thin lava...
The east face of Middle Sister is 350 m (1150 ft) high. Ice-sculpted pile of lavas at right, variously called "Black Hump," "Prouty Point," or "Step Sister," has 190 m of relief and consists of at least five flows.
The east face of Middle Sister is 350 m (1150 ft) high. Ice-sculpted pile of lavas at right, variously called "Black Hump," "Prouty Point," or "Step Sister," has 190 m of relief and consists of at least five flows.
View northwestward of South Sister volcano and unforested "Devils Chain" rhyolite lava domes.
The "Devils chain" is a string of nearly contiguous, virtually uneroded rhyolite lava domes and flows aligned north-south along a 5 km (3 mi) stretch on the southeast apron of South Sister. The largest of these is the Newberry flow (right center, below South Sister), only 2.5 km (1.5 mi) from the summit of South Sister.
The "Devils chain" is a string of nearly contiguous, virtually uneroded rhyolite lava domes and flows aligned north-south along a 5 km (3 mi) stretch on the southeast apron of South Sister. The largest of these is the Newberry flow (right center, below South Sister), only 2.5 km (1.5 mi) from the summit of South Sister.
Videos
Tracking uplift near Three Sisters volcanoes, using semi-permanent GPS instruments
USGS geologist Dan Dzurisin is near Sisters, in Central Oregon, to set up portable GPS monitoring equipment to track something that's been going on for 25 years and still goes on today. It’s uplift, a subtle rise in the ground’s surface, in an area west of South Sister volcano.
USGS geologist Dan Dzurisin is near Sisters, in Central Oregon, to set up portable GPS monitoring equipment to track something that's been going on for 25 years and still goes on today. It’s uplift, a subtle rise in the ground’s surface, in an area west of South Sister volcano.