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|November 21, 2017|
With 8 threatening volcanoes, USGS says California deserves close monitoring
With the world's top volcanologists heading to Portland, Ore., on Aug. 14 for the first international volcanology assembly held in the U.S. since 1989, the many famous, prominent and dangerous volcanoes of the West Coast will be the subject of field trips and much discussion.
Throughout the Cascade Range to Southern California, the West Coast is home to most of the country's highest-threat volcanoes, as ranked by the United State Geological Survey. And California has its share.
While Mount Shasta unsurprisingly tops USGS's list of very-high threat volcanoes in California, there are seven other volcanic areas in the state that are also young, nervy, jacked up on magma and "likely to erupt."
Scientists know from geophysical and geochemical research that these volcanoes have molten rock, magma, "in their roots," said Margaret Mangan, Scientist-in-Charge at the California Volcano Observatory. "I call them the watch-list volcanoes."
As listed by the California observatory, the eight fall into three danger categories:
· Very-high threat: Mount Shasta, Lassen Volcanic Center and Long Valley Volcanic Region
· High threat: Clear Lake Volcanic Field, Medicine Lake Volcano and Salton Buttes
· Moderate threat: Ubehebe Crater and Coso Volcanic Field
In 2005, a national team led by John Ewert, a volcanologist with the USGS Cascades Volcano Observatory, established a system for deciding which of the United States' 169 young volcanoes are the most dangerous and most in need of monitoring. In the "Framework for a National Volcano Early Warning System," Ewert's team identified 57 priority volcanoes in the U.S.
Among the 18 "very high threat volcanoes," 11 are along the Cascade Range in three states (Alaska and Hawaii have the others):
· California: Lassen Volcanic Center, Long Valley Caldera, Mount Shasta
· Oregon: Crater Lake, Mount Hood, Newberry, South Sister of The Three Sisters
· Washington: Baker, Glacier Peak, Rainier, St. Helens
"We live on a fascinating planet," Ewert said of the likelihood of eruptions along the West Coast, "and one of the reasons it is fascinating is that it is dynamic. The entire surface of the Earth is in motion and sometimes people have a hard time wrapping their head around that. We have big earthquakes. We have volcanic eruptions, tsunamis. All these things happen."
Pulse of the volcano
The volcano threat list was created, Ewert explain, not simply to alert people that the Earth is petulant but too set a foundation for determining which of the country's volcanoes need extensive monitoring.
He said the team used 25 factors to determine a volcano's danger status: What has the volcano done in the past? What's its modus operandi? When does it tend to erupt? What kind of phenomenon does it produce? Lahars (mud slurries of ice, rocks and other debris)? Pyroclastic flows (hot gas, rock and other stuff out of the volcano)? Is it a highly explosive volcano? How active is the volcano right now? Are there seismic swarms? Is it emitting hot volcanic gases? Is the edifice changing its shape (deformation)?
In addition to the geophysics of a volcano, the team examined how many people live or work near it, plus the amount and type of infrastructure has been built up around it ... power generation, port facilities, etc.
The team also considered, What is the aviation exposure? How many flights a day pass through the volcanic airspace?
"If it is an explosive volcano," Ewert said, "we asked how close is it to an airport and what is the daily passenger load of the airport? Recall in 2010, the eruption of the Eyjafjallajökull in Iceland shut down European airspace for over a week. That ran up about a $10 billion impact cost. Given the fact that an explosive eruption can put an ash cloud up to cruise altitude in five minutes or less, that volcanic airspace is an important thing to take into consideration."
Mangan said California had plenty to worry about in this regard as well.
"Over the northern California volcanoes, the data from FAA suggests that there are a couple hundred jumbo jets on flight-lines that pass over those three volcanoes on a daily basis," she said. "And, likewise there are a couple hundred jumbo jets that are flying over Long Valley Volcanic Region as well."
For all these reasons, Mangan said, the eight riskiest volcanoes in California need monitoring.
"... so that we can forecast eruptions, essentially keep our finger on the pulse," she said. "The best network, the optimized network that we currently have, is in the Long Valley Volcanic Region. It is arguably one of the best in the nation. It is also one of the most restless volcanic areas currently."
Michael Clynne, with the U.S. Geological Survey's Volcano Science Center and considered the world expert on all things Lassen, said the most recent volcano to erupt in the state, Lassen Peak, sits in the middle of a region ready to blow.
"The Lassen Volcanic Center is active and it will erupt again," he said during a public lecture published on YouTube. "It's only a matter of time. The Lassen Volcanic Center has had at least 13 eruptions in the last 100,000 years. That doesn't sound like very often. It's a recurrence interval of about 7,500 years. However there have been three eruptions in the last 1,100 years ... So the eruptions are not evenly spaced in time ... Volcanic activity is episodic.
"So, Lassen will erupt again. And maybe if some of us are lucky, it will be in our lifetime." (Source: The Chronicle)
Story Date: August 14, 2017