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Ape Cave Hike

From Oregon Hikers Field Guide

Highlighting the Lower Cave (bobcat)
Upper and lower decks, Lower Cave (bobcat)
Crawling in a side passage, Upper Cave (bobcat)
The "Skylight" in the Upper Cave (bobcat)
Breakdown in the Upper Cave (bobcat)
Lava flow along the return trail from the Upper Cave (bobcat)
Approximate alignment of Ape Cave and the hiking trail (bobcat)
  • Start point: Ape Cave TrailheadRoad.JPG
  • End Point: Upper Ape Cave Entrance
  • Hike Type: Out and Back (Lower Cave); Loop (Upper Cave)
  • Distance: 2.0 miles (Lower Cave); additional 2.7 miles (Upper Cave Loop)
  • Elevation gain: 180 feet; 640 feet with Upper Cave
  • High Point: 2,485 feet
  • Difficulty: Easy (Lower Cave); Moderate (Upper Cave)
  • Seasons: all year
  • Family Friendly: Yes
  • Backpackable: No
  • Crowded: Yes



NOTICE: Exploring Ape Cave is now on a timed reservation system. Reserve your two-hour slot on Recreation.gov.

Ape Cave, at 2.5 miles, is one of the longest lava tubes in North America and also one of the most accessible long lava tubes although it was only discovered in 1946. The lava tube formed about 2,000 years ago in an unusual lava flow down Mount Saint Helens’ south flank. About 450 years ago, a lahar flowed through the tube and plugged Ape Cave at its lower end. Many visitors come to explore the cave, which can be done all year. (In winter, the road is open to the Trail of Two Forests, 0.8 miles below the Ape’s Headquarters.) However, not all are well-prepared. While most of the Lower Cave is an easy walk, the Upper Cave involves a great deal of scrambling over jagged lava blocks. There is also the option to crawl into several side tunnels along the way.

WARNING: Bring clothing layers: it’s 42˚ inside the lava tube. Wear rugged outer clothing, such as jeans, if you are going to crawl. Bring one headlamp and a spare flashlight per person; it is also advisable to rent a lantern at the Ape’s Headquarters ($5)—their lanterns have a wire mesh that protects the mantles, rather than glass, which could shatter in the cave. Wear protective gloves if you’re doing the Upper Cave. Camera lenses will fog over as you approach exits and vents. It takes about four hours to fully explore the entire lava tube.

A short trail leads to the information kiosk at the Main Ape Cave Entrance. Descend into the lava tube on two flights of stairs. Heading down the Lower Cave, you walk under 30-foot ceilings. The “railroad track” formations were created from the collapse of a small lava tube inside the larger one. Openings and crevices can be explored for some of the cave life, such as crickets, grylloblattids, and fungus gnats. The ‘Meatball’ is a blob of lava that dropped off the ceiling, floated down the running lava, and got stuck at a narrow section. Sand from the lahar that plugged the cave forms the floor at this point. The final section of the Lower Cave has two levels. If you can get a boost up, try the upper level, which forms its own tunnel for about 20 yards but involves some commando-style wriggling. On the lower section, you can crawl down as far as a human body can go and then it’s time to turn around.

To do the Upper Cave, go beyond the lower flight of stairs at the Main Ape Cave Entrance. The first major feature here is a 90-foot wide ‘room.’ After this, you will cross three large rock piles or ceiling collapses, know as ‘breakdowns.’ Negotiate these carefully as not all the rocks are stable and many are sharp. There are side passages and crawlways to explore in this area. From one, you will get a rush of warm air from a vent. Come to the first lava fall. This is a sheer eight-foot climb using footholds. There are a couple more rock piles and another lava fall. You will pass beneath the ‘skylight,’ with its walls coated with green moss and ferns waving at the opening. There are a couple more large breakdowns and another lava fall before you reach the second skylight, which has a ladder leading to the upper exit.

One more section of the lava tube is beyond the upper exit. The cave opens out and you need to clamber over a large breakdown. The floor of the cave here is a solidified lava flow. Unfortunately, the walls here have been disfigured by graffiti (2012). Soon reach the amphitheater at the end of the cave and return to the Upper Ape Cave Entrance.

After climbing out of the cave, head down hill on the Ape Cave Trail #239. The path passes small lava tubes and also lava sinkholes. It enters shady woods of mountain hemlock, silver fir, noble fir, Douglas-fir, and western red-cedar with a salal and huckleberry understory. Soon you walk below a ridge of lava glowing with vine maple in the fall. You pass through an open area rimmed with lodgepole pine, slog through a sandy lahar outwash area colonized by alders, and then enter cool, mature forest. There are two creeks, usually dry in the summer and fall, to cross and you reach the Lower Cave entrance and then Ape’s Headquarters.

At 2.5 miles in length, Ape Cave ranks 37th in the world, 20th in the U.S., 6th in the Western Hemisphere, and 3rd in the continental U.S.

The longest lava tube in the Western Hemisphere is the Ferrocarril-Mina Inferior in Mexico at 4.06 miles.

The longest lava tube in the world is the Kazumura Cave in Hawaii at 40.7 miles. (The top five and 22 of the world’s 50 longest lava tubes are in Hawaii.)

The longest lava tube in the continental U.S. is the Deadhorse Cave, home of the “Masochist Maze”, near Mt. Adams, Washington, at 2.74 miles.

Source: World's Longest Lava Tubes by Bob Gulden

During the winter, you can only drive as far as the Trail of Two Forests Trailhead (Sno-Park permit required). Hike, ski or snowshoe from there the 0.7 miles up to Ape Cave.

Fees, Regulations, etc.

  • Northwest Forest Pass (or America the Beautiful Pass) required
  • Timed reservations to enter the cave ($2 processing fee); see Recreation.gov
  • No dogs, food, or alcohol in the caves; go to the restroom before you go down; carry enough light; wear clothing layers


  • Maps: Hike Finder
  • Green Trails Maps: Mount St. Helens, WA #364
  • Green Trails Maps: Mount St Helens National Volcanic Monument, WA #332S
  • U.S. Department of Agriculture, Forest Service: Gifford Pinchot National Forest
  • U.S. Department of Agriculture, Forest Service: Mount St. Helens National Volcanic Monument & Administrative Area
  • National Geographic Trails Illustrated Map: Mount St. Helens - Mt. Adams

Trip Reports

Related Discussions / Q&A

Guidebooks that cover this hike

  • Hike It Baby by Shanti Hodges
  • Day Hikes in the Pacific Northwest by Don J. Scarmuzzi
  • 100 Hikes: Northwest Oregon by William L. Sullivan
  • Washington Hiking by Craig Hill
  • Pacific Northwest National Parks & Monuments: The Creaky Knees Guide by Seabury Blair, Jr.
  • Best Hikes Near Portland by Fred Barstad
  • A FalconGuide to Mount St. Helens by Fred Barstad
  • Pacific Northwest Hiking by Craig Hill & Matt Wastradowski
  • Day Hiking: Mount St. Helens by Craig Romano & Aaron Theisen
  • Take a Hike: Portland by Barbara I. Bond
  • Best Hikes With Kids: Western Washington by Susan Elderkin
  • Best Hikes With Kids: Western Washington & the Cascades by Joan Burton
  • 95 Virtual Hikes of the Gifford Pinchot National Forest and the Mt. St. Helens National Volcanic Monument by Northwest Hiker
  • Best Short Hikes in Washington's South Cascades & Olympics by E.M. Sterling & Ira Spring
  • Day Hiking: South Cascades by Dan A. Nelson and Alan L. Bauer
  • Washington's South Cascades' Volcanic Landscapes by Marge and Ted Mueller
  • Portland Hikes by Art Bernstein and Andrew Jackman
  • Exploring Washington's Wild Areas by Marge & Ted Mueller
  • Washington's Columbia River Gorge: Camping & Hiking by Tom Stienstra & Scott Leonard
  • Washington Hiking by Scott Leonard
  • Pacific Northwest Hiking by Scott Leonard & Megan McMorris

More Links

Page Contributors

Oregon Hikers Field Guide is built as a collaborative effort by its user community. While we make every effort to fact-check, information found here should be considered anecdotal. You should cross-check against other references before planning a hike. Trail routing and conditions are subject to change. Please contact us if you notice errors on this page.

Hiking is a potentially risky activity, and the entire risk for users of this field guide is assumed by the user, and in no event shall Trailkeepers of Oregon be liable for any injury or damages suffered as a result of relying on content in this field guide. All content posted on the field guide becomes the property of Trailkeepers of Oregon, and may not be used without permission.