Volcanic mountains

Geologists are closely monitoring rising magma beneath the Three Sisters volcanic region

PORTLAND, Ore. (KOIN) — The Pacific Northwest is well known for its stunning peaks and many peaks, but do the mountains move?

In one USGS Hazard Notification Monday statement, Cascades Volcano Observatory announced that their scientists had tracked an increase in the rate of ground uplift in the Three Sisters volcanic region.

Using satellite radar images and GPS units, USGS scientists tracked an increase in the rate of uplift for a region 12 miles in diameter, 3 miles west of South Sister Volcano. According to the USGS, data suggests the ground rose 0.9 inches (2.2 cm) from June 2020 to August 2021.

Scott Burnsprofessor of geology at Portland State University, told KOIN 6 News while episodes of increased uplift have already been observed in this region, the cause is what local scientists are excited about.

“The Three Sisters area is an area we’ve been studying for 25 years,” Burns explained. “It’s very exciting because magma is rising under the volcano…the last major volcanic eruption in Oregon 2,000 years ago occurred in this area.”

Although the catalyst for the current uplift is unconfirmed, geologists have been able to attribute earlier ground changes at the South Sister location to small pulses of magma accumulating about 4 miles below the earth’s surface.

According to Burns, increased uplift is not the only thing impacted by the observed magmatic intrusion.

Interferogram image made from InSAR monitoring, showing ground uplift from 1995 to 2001 in the Three Sisters. Courtesy of USGS

“We think the magma is rising about four miles below the surface. And, and so coupled with that, you’ll often have very small earthquakes,” Burns said. “In December and January, we had a series very small earthquakes, showing that there is a movement of magma. The question is what type of magma will it be and what type of volcano?

Prior to the recent surge, the USGS said the uplift rate at the South Sister location had would have slowed down since scientists first recognized the phenomenon in the mid-1990s.

“From 1995 to 2020, the area has increased about 12 inches (30 centimeters) at its center,” the USGS said in a recent statement. “Although the current rate of uplift is slower than the peak rate of about 2 inches per year measured in 1999-2000, it is significantly faster than the rate observed for several years prior to 2020.”

Despite the excitement, the USGS and Burns said the public was not in immediate danger. The volcano’s status is currently listed as “green” and there are no signs of an imminent eruption.

“While any magmatic intrusion could eventually lead to a volcanic eruption, an eruption would likely be preceded by detectable and more vigorous earthquakes, ground movement (deformation), and geochemical changes,” the USGS said. “In general, when magma moves upward during an intrusion, it causes continuous or accelerated uplift, fractures rock to generate earthquake swarms, and releases significant amounts of volcanic gases, such as carbon dioxide. We are not currently detecting any of these signs.

Burns told KOIN 6 News that a team of scientists from the Cascades Volcano Observatory will continue to closely monitor uplift at the site and be ready if a threat is detected.

“We have great maps for the whole Three Sisters region,” Burns explained, “So if he[the volcano] comes back to life, we will know which people will have to step aside and prepare for it.

He continued: “The good news is that we are prepared for it… We are still ‘green’, but things are coming back to life now. Mother Nature is writing her own history book, so it will be interesting to see what she comes up with this time.