The World’s Hottest Hydrothermal Fumarole
Feel the breath of an active California volcano.
The Wonder Fumaroles are fissures in the Earth’s crust that spew steam and volcanic gas. Scientists measured the temperature of the steam jetting from Big Boiler, the largest fumarole in California’s Lassen Volcanic National Park, at 322°F, making it one of the hottest vents in the world.
The Way Start at Lassen’s Bumpass Hell parking area, 2.5 hours northeast of Sacramento. From the trailhead, you’ll climb 500 feet in the first mile, then descend .5 mile into the most thermally active area in the park. Big Boiler is easy to spot with its steam plume rising 30 feet skyward. You’ll catch the smell of rotten eggs, too–that’s hydrogen sulfide, a gas released by the magma below. Burbling mud pots and bright yellow crystalline sulfur deposits line the trail. nps.gov/lavo