Heed the warnings!
Long Valley is a super volcano, measuring 11 miles N-S and 20 miles E-W.
The movie, Dante's Peak, was based upon the monitoring of Long Valley, and I knew the volcanologist that consulted on the film.
It is also the sight of one of California's largest ski resorts, so real estate agents and town officials forced the U.S Geological Survey to stop issuing activity warnings. Nonetheless, carbon dioxide emissions are common, almost killing a U.S Forest Ranger several years ago. Micro earthquakes (a sign of magma moving underground) are also common.