For years, California has been preparing for the "big problem" – the magnitude 6.7 or more earthquake that is expected to have repercussions across the state this century. But there is another deadly threat that is almost as likely – and to which people can be much less prepared.
According to a report by the US Geological Survey (USGS) released Monday (Feb. 25), a small to moderate volcanic eruption could occur somewhere in California in the next 30 years. This forecast is based on 5,000 years of records of volcanic activity. About 200,000 people live or work in an area threatened by eruption, and millions of people visit each year, according to the report.
In comparison, there is a 22% chance that an earthquake at the San Andreas Fault, sometimes called "the most serious," strikes in that span of time.
"The risks of damage from earthquakes, landslides, floods, tsunamis and forest fires are widely recognized in California," researchers wrote. "The same can not be said of volcanic eruptions, even though they occur in this state as often as the largest earthquakes of the San Andreas Fault."
There are systems in place to detect potential volcanic eruptions – but it is important to understand the dangers in some parts of the state to reduce the damage and loss of life resulting from such events, they wrote.
According to the report, experts estimate that eight volcanic areas are "threatening" for people or property nearby. At least seven of the eight volcanoes are at the top of the magma and are therefore considered "active". [Countdown: History’s Most Destructive Volcanoes]
These include Mount Shasta, Medicine Lake Volcano and Lassen Volcanic Center in Northern California; as well as Salton Buttes near the southern border, have erupted over the past 3,000 years and are considered high to very high risk areas. The Long Valley volcanic region in the east has also erupted during this period, but is considered moderate to very high risk. And the Clear Lake volcanic field north of San Francisco is also considered high to very high risk, although it has not broken out in the last three millennia.
According to the report, a volcano can cause considerable damage, even if it is not unleashed. An erupting volcano can cause ballistic rock rains, rapid currents of ash or lava called pyroclastic flows and acid rain. However, even volcanoes that are not erupted can present risks: the lands around the volcano can be unstable and cause landslides, for example.
Although these effects are felt closest to the site of an eruption, landslides and floods can reach more than 80 km and even ash falls can reach areas 1,000 km (1,600 km). ), according to the report.
"Volcanic hazards are likely to be more than a local problem, confined to a single county or region," the report says. "A future eruption in northern California, for example, could have a negative impact on the natural resources and infrastructure important to our water, energy and transportation systems, and will certainly require some effort. Intervention involving multiple jurisdictions. "The eruption itself, which increases in intensity and declines over time, can last for months, years, or decades, as well as its sequelae.
Although volcanic eruptions can not be prevented, they can sometimes be predicted.
The USGS California Volcano Observatory uses GPS receivers to record soil deformations, seismometers to measure tremors and spectrometers to detect soil gas emissions. According to the report, an increase in activity on one or the other of these measures could be the first sign of the upcoming appearance of a volcano.
"Although eruptions can not be stopped, measures to limit exposure and strengthen tolerance can make society less vulnerable to their effects," they wrote. This includes evacuating areas of danger during an eruption, making the infrastructure more resistant to its effects, quick cleaning after the event, diverting lava or removing combustible materials from its path. In the event of ash falling, people can wear masks against particles, avoid driving, isolate buildings, shelter livestock and shelter on site.
Originally published on Science live.