Avalance lilies color the trail near Plummer Peak in Mount Rainier National Park.
Are the people of Washington inevitably doomed by an unexpected explosion of one of the most dangerous volcanoes in the world?
“What (studies) really show is lots of safe areas around Mount Rainier — we’re not all doomed,” said Pat Pringle, professor emeritus at Centralia College. “Really. The good thing about them is that we know where these lahars are going to go because they behave (according) to the laws of physics.”
Pringle’s reassuring comments were part of a comprehensive account and analysis of the geologic history of Mount Rainier and a discussion about whether state residents should be concerned about its impending eruption at a Sept. 24 History Pub gathering at Centralia’s McMenamins Olympic Club Theater.
Pringle referenced past studies, including the United Nations’ “Decade Volcanoes” project from the 1990s, while expounding on research efforts to achieve a better understanding of the 14,411-foot Cascade peak and highest mountain in Washington State.
“It takes decades to really get into the history of these volcanoes. This is sort of a snapshot view of what we know about Mount Rainier,” explained Pringle to an intimate crowd of fellow academics, researchers and college students.
“I’ll just talk a little bit about the hazards— the good and the bad news. So, the big idea here is that Mount Rainier is an active volcano and it’s uphill of many people,” said the 69-year-old geologist.
The UN’s undertaking prompted Pringle to go back and “take a second look” at Mount Rainier’s history left behind in its deposits.
What he and others learned by focusing on lahars (giant mudflows emanating from eruptions and non-eruptions) is that in its first 400-500 years, the 500,000 year-old mountain was pumping out “huge” lava flows before settling into a period of dormancy. About 200,000 years ago, however, the lava outbreaks returned. Since then, Pringle said, other active and inactive periods have come and gone over the past few centuries.
Pringle described how one of the mountain’s three major peaks, Columbia Crest was formed. The “cone,” he noted, was formed 5,000-6,000 years ago by an enormous lahar called the Osceola Mudflow. Should Mount Rainier experience an eruption, the lava “can go in any direction,” he said.
After flipping through images of entire forests of lahar-buried trees, the presenter and noted author of books on Mount St. Helens and Mount Rainier highlighted volcanic maps published by the U.S. Geological Survey that have identified numerous hazard areas.
“I’ve heard geologists on TV saying, ‘lahars are going to bury Seattle,’ ” he said. “People have to speak rationally about this and say that these flows behave like the laws of science, right? So, we have these maps that tell us about where future eruptions are likely to go; that’s called volcanic hazard mitigation.”
On that note, the featured speaker also mentioned monitoring devices— along with past history— are being used to measure the volcanoe’s vital signs and may very well be able to issue a prediction forecasting short-term expectations of activity.
The devices are acoustic flow monitors in the form of geophones that listen to the high frequency mud flows that typically measure between 50-80 Hz.
When asked about Mount Rainier’s last explosion in 1894, Pringle said the ash and pumice deposits were very thin, making them hard to find, and thus, leaving behind relatively few indicators of what transpired.
In fact, he went onto weigh in on the differences between Mount St. Helens and Mount Rainier, noting how the latter produces a different type of eruption that’s actually more of an explosion
Pringle concluded the evening session by delving into whether Mount Rainier is headed for an upswing of activity in the near future.
“You can’t tell, because I wouldn't trust the dormant intervals to tell us. The only way to tell you that it’s going to happen is (through) the vital signs … It’s not a cyclical phenomenon; it’s chaotic and I think that’s the key. We really just don’t see a pattern. It’s like my theory of the universe is lumpy. Every once in a while you come up to a cluster of matter and then nothing for a while,” surmised the local professor.
Pringle is the author of books on the roadside geology of Mount St. Helens and Mount Rainier, as well as many published papers and reports.
