Yellowstone geologist says recent earthquakes interesting but not dangerous

The 400 earthquakes that rumbled through Yellowstone National Park for a week through Jan.2 are nothing to fear said Yellowstone National Park Geologist Hank Heasler.

The so-called earthquake swarm that included earthquakes measuring 3.9 on the Richter Scale is not even as long and powerful as a similar swarm in 1985. But Heasler and his colleagues at the University of Utah and the U.S. Geological Survey spent several hours Friday on a conference call comparing notes and sharing their views on the latest geological event atop the largest known volcano in the world.

Yellowstone has several thousand earthquakes annually but this recent swarm is unusual. The park is under lied by a giant caldera from the last explosive volcanic eruption 40,000 years ago. If it were to happen again most of North America would be destroyed and the world would freeze under a shroud of ash for about two years.

So geologists like Heasler pay attention when the geothermal activity in the park becomes unusual.

“Looking at the data currently we don’t see any indication of volcanic activity,” Heasler told me Friday.

The last two explosive eruptions have come at 600,000-year intervals so some geologists say the next one is overdue. But there have been 30 relatively minor eruptions since then.

Most of the recent earthquakes have center around Yellowstone Lake, an especially hot and active geothermal region. Five miles below the lake lies a giant magma chamber, which scientists say has bulged upward about 60 feet over the last 50 years. But the latest earthquakes have not changed things noticeably, Heasler said.

“Scientists don’t currently see any indication of uplift,” Heasler said. “We’re not seeing a bulge at this time.”

The earthquakes triggered worldwide news reports because of the potential effects of a major volcanic eruption. But scientists expect the next volcanic eruptions in the park to be non explosive lava flows, which while destructive, would be likly limited to the park and perhaps surrounding areas.

Based on the observation of Heasler and his colleagues, authorities have kept Yellowstone’s volcanic alert level at green, which means they aren’t worried yet.

I remember the 1985 earthquake swarm. At around the same time Excelsior Geyser near Old Faithful, dormant since a steam explosion in the 1800s, came back to life. Pork Chop Geyser, exploded in 1989 and only came back to life in 2003.

The 1985 swarm lasted several months and the biggest earthquake was 4.5 on the Richter Scale, Heasler said. So we may be due for some more action before this one is over.

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Source: voices.idahostatesman.com