Lassen Peak: The Last Time California's Volcanoes Fired

The forest you are looking at here is one hundred years old. Before it grew, this hillside was bare volcanic debris.

Between nineteen fourteen and nineteen seventeen, Lassen Peak erupted. Intermittently, over three years, with a major eruption on May twenty-second, nineteen fifteen, that produced a lateral blast powerful enough to level a wide corridor of old-growth forest, generate a mudflow that raced downslope destroying everything in its path, and send an ash column hundreds of miles.

An innkeeper and photographer named Benjamin Franklin Loomis had been watching the eruptions from his lodge on the north side of the mountain. He photographed the eruption column on May twenty-second, producing what became the primary visual record of the event. Those photographs made it to Congress, and in August of nineteen sixteen, Congress established Lassen Volcanic National Park. It was the same year Congress created the National Park Service itself.

Lassen remains the southernmost active volcano in the Cascade Range, the chain that runs from northern California through Oregon and Washington into British Columbia. Before Mount Saint Helens erupted in nineteen eighty, Lassen was the most recent volcanic eruption in the contiguous United States. The system has not stopped. Geologists describe Lassen as dormant, not extinct. There is a distinction.

Walk the Devastated Area trail. The volcanic rock underfoot is what the nineteen fifteen blast left behind. The young firs pushing up through it are the forest returning to terrain scraped to stone a century ago.