Lava flows could be a reality in California
Hawaii eruptions remind us of our own volcanoes
Lassen Peak had been rumbling for days. Glowing hot rocks bounded down the slopes. Lava was welling up into a freshly created crater.
Then, on this day 103 years ago, it exploded in a way California would never forget. It created a gigantic mushroom cloud that reached an altitude of 30,000 feet, could be seen as far away as Eureka and Sacramento and sent volcanic ash as far away as 280 miles, reaching Elko, Nevada.
It was the first volcanic eruption in the contiguous 48 states since the founding of the United States, and the last until Mount St. Helens erupted on May 18, 1980.
And it was a reminder not only of how California is threatened by earthquakes, but how volcanoes are a part of life in a state that sits in the Ring of Fire. As the world focuses on the volcanic show in Hawaii, the Lassen Peak eruption offers a lesson of the threat closer to home.
“California is not just earthquake country. It is also volcano country,” said Margaret Mangan, the scientist in charge of the U.S. Geological Survey’s California Volcano Observatory. There have been 10 eruptions in California
over the last 1,000 years, and in any given year the chance of a major volcanic eruption in the state is about the same as the risk of a major earthquake on the San Andreas fault.
“Our nearly forgotten hazard is our volcanoes,” state geologist John Parrish once said.
Including the Lassen Volcanic Center, there are eight volcanic regions considered worth watching for future eruptions in California, according to the USGS, from the far north of the state to near the Mexican border. Most have been confirmed to have partly molten rock underneath them.
Some of California’s most scenic wilderness spots are threatened by volcanic activity. More than 190,000 Californians live within a volcano hazard zone; among them are people who live or work in the Long Valley region, home to Mammoth Lakes in Mono County, a favorite destination of skiers from Southern California, and areas in the shadow of Mount Shasta, such as the towns of Mount Shasta and Weed. Those cities are close enough to volcanoes that they may be in harm’s way in the next eruption, Mangan said.
Volcanoes in the Lassen, Shasta and Long Valley areas are capable of producing pyroclastic flows or surges when they do erupt — fast-moving flows of hot ash, rock and gas sweeping down the sides of mountains, of the type that killed 57 people when Mount St. Helens erupted in 1980.
Most of the volcanoes are far from California’s largest cities and several produce heat that’s used to generate electricity in what are
the world’s most productive geothermal power plants, such as the Salton Buttes 160 miles southeast of Los Angeles and the Clear Lake Volcanic Field 85 miles north of San Francisco, which powers the Geysers steam field.
But volcanic eruptions could have lasting repercussions that could affect all of California. Volcanic ash could bring down jetliners and disrupt hundreds of flights daily passing through Northern California or the Mammoth Mountain area. In 2010, the eruption of Iceland’s Eyjafjallajökull volcano forced the cancellation of 100,000 flights in a single week.
Volcanic ash, when wet, is conductive and can disrupt high-voltage lines that supply electricity to millions of California homes. Ash could A woman takes photos on a tour boat to view Kilauea volcano lava entering the Pacific Ocean as a steam plume rises, on Hawaii’s Big Island on Tuesday near Pahoa. disrupt travel on Interstate largest reservoirs 5, the main route between are close to the Shasta and California and Oregon, Lassen volcanoes. masking windshields and If there’s any good news, making roads slippery, even it’s that major volcanic activity impassable. And it could is usually accompanied contaminate water supplies by some warning to much of the state; California’s signs, and scientists have
become much better at forecasting major events before they happen, enabling authorities to sound warnings to reduce the chance of deaths.
“We aim to make that number zero,” said USGS volcano scientist Wendy Stovall.
Volcano scientists have done well so far at forecasting hazards associated with Kilauea volcano on Hawaii’s Big Island in recent weeks. After a lavacontaining crater collapsed, scientists tracked a pattern of earthquakes eastward, suggesting magma was on the move and would eventually come to the surface. It did so in the neighborhood of Leilani Estates, about 25 miles east of the volcano’s summit, where lava has destroyed dozens of structures. Scientists also correctly forecast the steamdriven explosions at the summit.
Volcano science has come a long way since the deadly 1980 eruption of Mount St. Helens, which is the most active volcano in the Pacific Northwest and is in a remote part of Washington state. Those who died generally had been within 15 miles of the volcano. There were signs that magma was moving underneath the volcano in the months before the eruption, but how it unfolded caught scientists by surprise.
California’s volcanoes were more prolific in prehistoric times. About 760,000 years ago, a super eruption occurred at what is now known as the Long Valley Caldera, erupting an astonishing 140 cubic miles of magma, covering much of east-central California in glowing hot ash and blowing ash as far away as Nebraska. (Mount St. Helens, by contrast, erupted only 0.05 cubic miles of material.) There is no sign that there is enough magma underneath Long Valley to cause another super eruption, Stovall said.
Sometimes it’s not the pyroclastic flows that prove so deadly; sometimes it’s the ice and snow quickly melting during the eruption that pose the greatest threat. The 1985 eruption of Nevado del Ruiz in Colombia killed 25,000 people — but was so deadly only because the melting water triggered mudflows. “They didn’t know it was coming. It happened at night,” said USGS volcano scientist Mike Clynne.
In the eruption of Indonesia’s remote Krakatau volcano in 1883, it was the top of the mountain caving in that triggered a tsunami that struck Java and Sumatra islands, killing as many as 36,000 people.