California will “inevitably” be hit by a volcanic eruption – and the effects could be disastrous, a new report claims. The document by the United States Geological Survey (USGS) said the risks of damaging earthquakes – and their potential to wreak havoc – are widely recognised across the state. But volcanic eruptions are actually as common as earthquakes along the San Andreas Fault but attract far less attention.
John Parrish, former State Geologist of California, said last year: “California is the most geologically diverse state in the nation. We are known for our earthquakes, landslides, and flood hazards.
“But our nearly forgotten hazard is our volcanoes.”
There are currently seven ’watch list’ volcanoes ranked as moderate, high or of a very high threat in California.
And nearly 200,000 people “live, work or pass through a California volcanic hazard zone on a daily basis”, the report warns.
The eruption of volcanoes such as Mount Shasta and the Salton Buttes have the potential to affect hundreds of thousands of people in the event of an eruption.
The volcanoes are the watch list, include Medicine Lake Volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake Volcanic Field, Long Valley Volcanic Region in Mono County, Coso Volcanic Field and Salton Buttes.
The report states: “The largest populations are around Mount Shasta (103,885), the four volcanoes in the Long Valley volcanic region (63,523), Clear Lake volcanic field (17,910), and the Lassen Volcanic Center (9,888).
“Smaller populations fall within Medicine Lake volcano (5,209), Salton Buttes (2,518) and Ubehebe Craters (111) hazard zones.”
At least 10 eruptions have taken place in the past 1,000 years.
The most recent one was the Lassen Peak eruption of 1914 to 1917 in northern California and future eruptions are inevitable.
The report said: “Based on the record of volcanic activity over the last five millennia, the probability of another small to moderate-sized eruption in California in the next 30 years is estimated to be about 16 percent.
“This is similar to the forecast for a magnitude 6.7 or greater earthquake specific to the San Andreas Fault in the San Francisco Bay region, which is estimated to be about 22 percent probability in 30 years, starting from 2014.”
Other activity could include toxic gas emissions, ground movement and the emergence of hot springs and geothermal systems.
The USGS California Volcano Observatory (CalVO) monitors the potentially hazardous volcanoes to help prepare and respond to volcanic activity.
Researchers monitor GPS receivers, seismometers and multi-gas spectrometers for signs of impending activity.
Ground deformation, seismicity and gas emissions all point to a possible eruption.
However, the report added it is difficult to predict when the eruptions are going to happen and can have catastrophic outcomes.
The report said: “Although volcanic activity can sometimes be forecast, eruptions, like earthquakes or tsunamis, cannot be prevented.
“Understanding the hazards and identifying what and who is in harm’s way is the first step in mitigating volcanic risk and building community resilience to volcanic hazards.”