Two earthquakes, of magnitudes 5.3 and 5.1 on the Richter Scale, occurred in Iceland in the early hours of Sunday, the country’s Meteorological Office said, and a 6.0-magnitude earthquake hit Napa, Calif., in the middle of the storied wine country.
No deaths were reported from any of the weekend’s quakes, but about a hundred people were evacuated in Iceland and more than 120 injured in California. Several buildings and utility structures were also badly damaged in the Napa earthquake.
Iceland’s Bárðarbunga volcano
The country issued a red alert warning, which means an ash-emitting eruption may be imminent. The Bárðarbunga volcano is rumbling and sending out hot magma beneath about 100 to 400 meters of ice in the Vatnajokull glacier. It might never break through the ice to send ash into the sky. It’s hard to say at this point.
The current volcanic activity is the result of more than 1,200 small earthquakes that have rocked the area over the past week. With all the hot magma under the glacier, the risk of flooding is also considered high, the BBC reports.
Iceland sits atop the Mid-Atlantic Rift Zone, where volcanic activity is frequent. Eruptions are triggered by the movement of Earth’s tectonic plates and by magma from deep underground pushing up to the surface.
National Geographic recently wrote about the volcanoes under Iceland’s glaciers and the problems they create for aviators and Earth scientists, here. “Eruptions that happen under ice are often more explosive than those that happen on dry land. The meltwater and the magma interact to form small particles of ash that can be blown high into the air,” the authors write.
These more explosive eruptions happened before and could happen with Bárðarbunga in this case. In 2010, an eruption of Iceland’s Eyjafjallajokul volcano caused more than 100,000 flights to be cancelled around the world due to the ash cloud sent into the air. This year, just to be safe, officials have declared a 185 × 260-kilometer no-fly zone around Bárðarbunga.
The eruptions aren’t considered dangerous to people on the ground, though. First, Iceland has taken steps to prepare its residents for volcanic eruptions, since they’re so common. And second, Bárðarbunga is located in a remote area about 320 kilometers east of the capital of Reykjavik. Nobody lives there, so the evacuations have been mainly for hikers. The main concerns are flooding and any possible disruption to air traffic.
The strongest earthquake in the San Francisco Bay area in 25 years struck Napa, in the center of California’s wine country, in the early morning Sunday, the San Francisco Chronicle reports.
“A magnitude-6.0 earthquake struck the North Bay early Sunday, injuring more than 100 people, causing extensive damage to dozens of buildings in downtown Napa and Vallejo and sparking a fire that destroyed six homes,” the story read.
The quake also ruptured water mains and gas lines, which impaired the ability of firefighters to put out fires that broke out after the 3:20 AM quake.
Gov Jerry Brown declared a state of emergency for southern Napa County. The epicenter was about 10 kilometers south of Napa, and the shaking lasted 10 to 20 seconds, according to the United States Geological Survey.
The Napa Unified School District canceled classes for Monday and said students wouldn’t be allowed to return to schools until the buildings were checked.
The depth of the earthquake was just under seven miles, and was followed by numerous small aftershocks, the USGS said.