About
The Hat Creek basalt lava flow erupted about 24,000 years ago, near the present site of Old Station, California, and flowed along the Hat Creek Valley. It reached the vicinity of Rising River Lake, about 20 miles north.
The flow generated lots of lavatubes, in which flowing lava crusts over while still-molten lava underneath drains out to leave a void. Most of the resulting tubes were small, a few feet or so in diameter, but at least one was world-class: Subway Cave. The dimensions in its main passage range from 6 to 17 feet high, and often more than 25 feet wide. There is plenty of room for a person to walk upright.
Unlike many lavatubes, the cave is often wider than it is tall. This is because the floor itself consists of the top of a lava flow that flowed through the cave. Either the cave didn’t drain out completely, or a later flow came along. Both situations have been observed in other lavatubes.
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Know Before You Go
Subway Cave is easy to find. The turnoff is on California State Route 89 about 0.3 mile north of its junction with CA-44, and is well marked. There is a large parking area at the trailhead, and the path to the cave entrance is also well marked. Concrete stairways at either end, installed at natural entrances formed by roof collapse, mean no scrambling is necessary. There are no installed internal lights, however; you must bring your own. An electric lantern is useful because it throws out a broad beam, but a headband lamp, which keeps the hands free, is also useful. Be sure to bring a spare light, too. The distance between the stairways is about 1/3 mile, so you will need a light.
No crawls or rappels are involved, but hiking shoes are a must on the ragged flow top in the cave. A jacket may also be comfortable, as the cave temperature remains around 46° Fahrenheit year-round. The cave is open dawn to dusk, typically beginning in later April. Finally, please no pets.
Spattercone Trail makes an interesting sidetrip while in the area. This is the place where the Hat Creek flow erupted, and is marked by lots of volcanic features including the eponymous spattercones. To get there, go back south on CA SR-89 1.8 miles, past the turnoff to SR-44 and through the village of Old Station, to a turnoff to a trailhead and parking area on the left of the highway. It is well marked. The trail includes interpretive signs on the volcanic features.
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Published
February 4, 2025
Sources
- Turrin, Brent D. , L.J. Patrick Muffler, Michael A. Clynne, Duane E. Champion, Robust 24 ± 6 ka 40Ar/39Ar age of a low-potassium tholeiitic basalt in the Lassen region of NE California, Quaternary Research 68, 96 – 110, 2007.
- Anderson, C.A., 1940. Hat Creek lava flow. American Journal of Science 238, 477–492, 1940.
