Volcanic activity taking place in Madera County

July 1, 2013 12:00:00 AM PDT
On a clear day in the Central Valley you can see Mammoth Mountain. The peak on the east side of the Sierra Nevada Mountains is part of a volcanic range that stretches into Madera County. There hasn't been a major eruption in thousands of years, but the threat is still there.

From the top of Mammoth Mountain, the view is incredible, but we're focused on the Red Cones, about 2,000 feet below. These cinder cones are the two youngest volcanos in this chain. They last erupted about 9,000 years ago and they are just inside the Madera County Line.

Stuart Wilkinson explained, "The volcanic activity started with the eruption of the long valley caldera roughly 750 thousand years ago, and that was a cataclysmic eruption that sent ash as far east as Nebraska."

Wilkinson is a geologist with the U.S. Geological Survey; his job is to monitor the continuing seismic and volcanic activity in the caldera which encompasses the entire Mammoth Lakes area.

"In more recent times the structure of Mammoth Mountain was formed 150 to roughly 50 thousand years ago. And roughly 100 thousand years ago was when the Devil's Postpile formation was emplaced," said Wilkinson. "In more recent times we had activity beneath the flanks of Mammoth Mountain and gas emissions from that activity caused CO2 emissions to occur here in the Horseshoe Lake area."

Dead trees above ground are evidence something is going on underground. The volcanic activity is pushing carbon dioxide gas up into the trees killing their roots. You can't see it or smell it but if you laid down long enough it would likely kill you.

"CO2 is deadly so you do want to be careful," said Wilkinson. "You don't want to lay down in a gully or a low area because the CO2 is heavier than air and it will collect in gullies and what not."

In 2006 three members of the ski patrol were killed when they fell into a carbon dioxide vent on Mammoth Mountain.

The river water is heated to nearly boiling by molten rock five miles below the surface. It used to be a popular place to swim until people were scalded to death.

Action News spoke with a tourist, Michelle Erickson told us, "Well, that's the people who drink too much beer and get in right by the scalding waters."

Erickson has been coming here for years. She thinks the waters are safe if you pick the right spot. But after the water started getting hotter here a few years ago, they are supposed to be off limits to beer drinkers and anyone else. Volcanic pressures are heating water, releasing gas, and causing earthquakes.

John Cano said, "There may be 30 or 40 earthquakes a day in this area."

Cano is a longtime resident, and lived through the last big one here. He said, "I was here in the eighties they said it was a 7.0 they downgraded it to a 6.8 but I got tell you it scared the heck out of me."

The quake caused $2 million in property damage and several injuries but no deaths. Despite frequent small quakes, the town of Mammoth Lakes and especially Mammoth Mountain volcano are popular tourist destinations.

Wilkinson and other geologists with the U.S.G.S. volcano hazards program are keeping an eye on what's happening underground, just in case.

Action News asked, "Well what are the chances it's going to erupt again?"

Wilkinson replied, "Hard to say, chances of a significant eruption here are about one in one hundred, similar to the chances of a major earthquake on the San Andreas Fault near San Francisco."

Fear of the big one isn't keeping people away from the Bay Area, and the spectacular beauty in the Mammoth Lakes area, makes a visit to the volcanoes in our backyard a trip worth taking.


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