Ape Cave
Descend into a pitch-black lava tube created by an ancient Mount St. Helens flow, choosing between a gentler lower passage and a strenuous scramble.
Artwork inspired by Doris Totten Chase
Ape Cave is a lava tube formed when the surface of a Mount St. Helens lava flow hardened while molten rock continued moving beneath it. The emptied conduit extends for more than two miles, preserving flow textures, breakdown, and places where the tube changed shape. The cool darkness is the experience; there is no installed lighting inside.
The Lower Cave is the shorter, less technical choice, while the Upper Cave requires boulder scrambling and climbing an approximately eight-foot lava fall before an overland return. Every person needs two dependable light sources, warm layers, sturdy footwear, and enough time. Avoid touching cave surfaces unnecessarily and clean footwear before and after to reduce ecological contamination.
- Setting
- Cougar, Washington
- Reservation
- Timed entry and a recreation pass are required in the managed season
- Allow
- 1–4 hours
Quick guide
- Choose the route
- Lower walk or strenuous Upper Cave scramble
- Bring
- Two lights per person, warm layers, and sturdy shoes
Read the lava tube
- Formation
- Look for a hardened roof above the former path of moving lava.
- Texture
- Notice flow lines, ledges, breakdown, and changing passage dimensions.
- Route
- Do not enter the Upper Cave unless the entire party can scramble and climb.
- Protection
- Pack out everything, leave rock in place, and clean gear between caves.
Good to know
Phone lights are not sufficient backups in a wet, uneven cave. The Upper and Lower routes differ sharply in difficulty, and the paved forest approach does not make the underground passage accessible.
Notice these
- long lava tube formed by a Mount St
- dark basalt passage and ceiling textures—not surface scenery
- 1–4 hours