Sulphur Works, Tophet Hot Springs
Sulphur Works, also on record as Tophet Hot Springs, is a roadside thermal area inside Lassen Volcanic National Park, Plumas County, about nineteen miles from Chester. The water is near boiling, 199 degrees in the record. It will scald on contact. Nobody soaks here. It is a place you stand back from and watch, on National Park Service land with open access.
Lassen Peak Highway runs within two hundred feet. Close to seven thousand feet up, and the snow numbers are enormous: more than seventeen feet in an average winter, on forty-six inches of precipitation. Averaged across the year the thermometer sits in the mid forties.
The record names midwinter as the best season, which sits oddly against seventeen feet of snow; check road status with the park. Manzanita Lake Group Campground is about six miles off. Do not approach the water; it is hot enough to cause severe burns in an instant. The USGS sample is from 1981 and reads slightly acidic.
The site goes by two names on file, Sulphur Works and Tophet Hot Springs. It lies within Lassen Volcanic National Park, and the U.S. Geological Survey sampled the water in June 1981.
Aircraft with laser scanners measured this ground to within inches. The scan strips out trees and buildings, leaving the bare shape of the land around Sulphur Works, Tophet Hot Springs.
Drag the handle to compare the two views. The orange dot marks the spring, in a frame about three quarters of a mile wide.
- Setting
- Hillside
- The spring sits on a steep slope that climbs to the west.
- Highest ground nearby
- 584 ft above the spring
- Within a quarter mile, to the west
A slice through the ground from northwest to southeast, about 0.6 miles end to end.
Elevation data: USGS 3D Elevation Program. Aerial imagery: USGS The National Map. Public domain.
That's about 1½ times the US average of 65. It's higher than at 41% of the springs on this site.
Heat flow measures the warmth working its way up through the ground from deep inside the earth. Where it runs high, rain and snowmelt that seep down through cracks in the rock come back up hot.
See every spring on the geothermal heat map →
Heat flow estimate: Stanford Thermal Earth Model (Aljubran & Horne, 2024), CC BY 4.0.
The water at Sulphur Works, Tophet Hot Springs is slightly acidic (pH 6.1) with 88 mg/L total dissolved solids.
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Overview Manzanita Lake Group Campground is located at the west end of Loop B in Manzanita Lake Campground, the largest campground in Lassen Volcanic National Park. It is within walking distance of scenic Manzanita Lake, a popular fishing and family destination, and offers impressive views of Lassen Peak, the largest volcano in the park at 10,457 feet.Recreation Manzanita Lake is popular with fly fishermen who enjoy the catch-and-release policy. Non-motorized boating is also permitted and kay...
Sulphur Works, Tophet Hot Springs sits at 6,932 feet above sea level, way above the mile-high mark. You may not feel the altitude strongly, but hot water still dehydrates you faster at elevation. UV is about 28% stronger than at sea level, so bring sunscreen and drink more water than you normally would.
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Sulphur Works, Tophet Hot Springs is road-accessible, so you can bring more gear. The water is dangerously hot, so bring water shoes and test pools carefully. Cold air temperatures make a changing robe or warm layers essential.
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