What Magma Moving Beneath Oregon Volcano Tells Us About Future Eruptions

Magma beneath land close to the South Sister volcano in Oregon has caused an uplift in the area, the United States Geological Survey (USGS) said, offering potential clues to future volcanic activity.

The uplift was detected by satellites used by the USGS to monitor the region. The data they collected showed an uplift of about 0.9 inches occurred between the summer of 2020 and August 2021 across a space 12 miles in diameter, roughly three miles away from South Sister.

Magma uplift can indicate volcanic activity below the surface of the Earth. A research paper published in Frontiers in Earth Science in January 2021, which examined the Three Sisters Volcanic Center in Oregon (where the South Sister volcano is), found that changes to the uplift behavior in the area could be considered an important indicator of future volcanic activity.

However Jon Major, the scientist-in-charge at the USGS Cascades Volcano Observatory, said that the activity did not have scientists overly concerned about a possible imminent eruption at the site.

"The current uplift at Three Sisters is small and progressing very slowly, so we do not expect an eruption soon. We infer that emplacement of magma at depths of about 4 miles below ground is responsible for this uplift. If that magma was to work its way closer to the surface and possibly head toward eruption, we would expect to see other signs indicting as much," he told Newsweek.

"As magma got closer to the surface we would see more rapid uplift, possibly focused in a narrower area. The magma would break rock to make pathways to the surface and so we would see increased numbers and sizes of earthquakes as well as a shallowing of earthquake source areas. Magma would also release its stored gasses, and we would see an increase in gas output. These are among the typical signs we look for before an eruption; we see no such signs at present," Major said.

South Sister last erupted over 2,000 years ago, spewing ash and thick viscous lava flows down its flanks. These impacts are still visible today.

Major said that the most recent uplift at the site occurred during the mid-1990s and continued for more than 25 years, bringing a series of earthquakes with it that were so small most could not be felt by humans.

The scientist said that if the most recent uplift reported by the USGS followed the same pattern, it would likely slow down.

"Small bursts of episodic earthquakes may occur as the crust adjusts to magma input... if the magma started working its way to even shallower depths and approached the surface, we would expect to see increases in earthquakes, uplift, and gas release," he said.

Stock image of South Sister volcano
Stock image of South Sister volcano. The volcano last erupted around 2,000 years ago, the USGS said. RobertCrum/Getty Images