Little Earthquakes Shake Mount Hood

The mountains on our horizon are shaking. Should we freak out?

It seems like just last week that we reported that swarms of earthquakes were "recharging" Mount St. Helens (because it was). But now, it appears, the swarms are getting closer.

According to KATU, starting Sunday evening "the U.S. Geological Survey says there were nearly three dozen quakes recorded north of Highway 30, along the south side of the mountain."

The small earthquakes—the largest was magnitude 2.4—continued into Monday.

Reached by phone in Seattle, Joan Gomberg, Research Seismologist with USGS, isn't too worried.

"There is indeed a little swarm going on under Mount Hood," Gomberg says. "It's being watched carefully."

Earthquake swarms are basically just what they sound like: a lot of little earthquakes of similar size, without the shock-aftershock pattern of larger earthquakes.

Gomberg says that while these earthquake swarms aren't common, they aren't unprecedented.

"Swarms are pretty typical of volcanoes," she says, reminding us that the high Cascades contain many active volcanoes.

When asked whether the swarm at Mount Hood was related to the swarm at Mount St. Helens, Gomberg says, "There's certainly nothing we can measure that connects the two."

She adds that while the swarm at St. Helens is caused by recharging magma, the cause of the Hood swarm is less clear.

"Either magma is moving or gas has heated up or cooled down so that the pressure has changed," says Gomberg.

"It doesn't mean at all that it's getting ready to explode," she adds. "It's just telling us that the volcano is alive and well, but at this point there's no catastrophe on the horizon that we can tell."

No catastrophe on the horizon, just a shaking mountain.

"We'll just keep watching it," says Gomberg.

Yeah, and so will we.