New ages confirm that the youngest Eagle Lake volcanic rocks erupted 130-125 thousand years ago

USGS scientists recently released a report about the age of the youngest volcanic deposits at Eagle Lake, CA, in which they concluded that three of the most recent lava flows erupted 130, 127 and 123 thousand years ago. The scientists used stratigraphic, paleomagnetic, and 40Ar/39Ar dating techniques to measure the ages.

Eagle Lake is one of 14 sites in California that was previously identified for potential future volcanism. Originally, geologic mapping was used to interpret the ages of the youngest flows at Eagle Lake. The interpretations from mapping led scientists to believe that eruptions there might have occurred in the Holocene (last 10,000 years). However, the new precise ages show that the flows erupted over a hundred thousand years ago in the Pleistocene. Geologists tend to consider only volcanoes with Holocene-age eruptions to be young enough to potentially erupt again, therefore the likelihood of volcanism from Eagle Lake in the future is extremely low.

Knowing the age of the most recent volcanic eruptions throughout the state helps the California Volcano Observatory (CalVO) plan for, and efficiently deploy, its volcano monitoring resources to locations that have the greatest potential for activity. As a result of the new research at Eagle Lake, CalVO scientists have reconsidered its priority as a location that needs monitoring equipment.