Gabbro B-Sides

I went camping this weekend in a natural disaster waiting to happen. Seven hundred and sixty thousand years ago, a volcano went off in Eastern California, covering the western United States with ash and leaving behind a 15 km x 30 km caldera. That volcanic system is still active - there’s a slowly-growing bulge in the middle of the caldera, which indicates the presence of an expanding magma chamber. As the magma loses some of its dissolved gasses, a gentle CO2 breeze wafts up from the rock on nearby Mammoth Mountain, to the great misfortune of the mountain’s trees and a couple of skiers. And of course, as magma shifts around, it creates frequent earthquakes.

Most importantly, though, there are hot springs. Late Holocene anthropogenic bioturbation has created comfortable soaking pools throughout the valley. Occasionally, these springs will kill you - more than a dozen people have been fatally scalded at Hot Creek since 2020, and the area has been closed to swimmers since it resumed geysering in 2020. Other hydrothermal sites, however, are less fatal and less closed.

Bizarrely, the news that Long Valley is an active volcano has been downplayed by the local tourism bureaus. The emergency evacuation route from Mammoth Lakes has been labeled a “scenic loop”. Business suffered in the early 2020s, after the USGS issued an eruption warning. Sure, the area is at risk; although the next eruption is likely to be small, continuing the string of little cinder cones that run from Long Valley to Mono Lake, a smaller eruption would be bad enough. Ski boom or no ski boom, I’m not scrambling to invest in mountain real estate. But as a tourist, the odds are very low that an eruption will occur during the weekend you happen to be visiting. And did I mention there are hot springs?

I shouldn’t make the area sound too enticing, though, or the tubs will fill up. Long Valley is a large and explosive volcano. It will kill you. Stay away.