Study suggests past eruptions were more intense than earlier believed
EUGENE, Ore. (KTVZ) — A hiker’s pack usually gets lighter over time as they plow through trail mix and water, but Annika Dechert likes to joke that hers gets heavier.
As an earth sciences graduate student at the University of Oregon, she’s picking up clues to the eruption history of South Sister volcano in the Oregon Cascades, helping scientists better understand its possible future risk. Those clues: 10-pound chunks of crystal-studded rocks, ejected during past eruptions spanning 39,000 to 2,000 years ago and hauled off the volcano by Dechert and a team of volcanologists.
South Sister, which sits in a wilderness area popular for outdoor recreation, is classified as a “very high threat” by the United States Geological Survey. By analyzing crystals in volcanic rocks, Dechert and her colleagues have now found that South Sister was historically active with greater intensity over a shorter time window than previously believed. And they’ve shown two distinct periods of eruptions in South Sister’s past that appear to come from different sources.