Mt. St. Helens Ape Caves

Get Outside in a Cave...Mt. St. Helens Ape Caves


The full experience at Mt. St. Helens Ape Caves includes the easy exploration of a spacious lava tube, followed by more difficult travel through a smaller, longer, and more rugged lava tube to an exit. Then, enjoy an easy return hike winding through shady forest and crusty lava formations.



Mt St Helen's Ape Caves

Before you go, make sure everyone in your party is aware of the restrictions and conditions: No food, pets, smoking, or rock collecting. Do not touch the walls, which harbor cave “slime”, a food source in the cave’s delicate ecosystem. The temperature is a constant 42 degrees F. The ceilings are drippy, and there may be puddles. Bring 2 or 3 light sources and spare batteries. No cave can ever be considered completely safe.

A short distance from the parking lot, enter the large cave entrance and descend two staircases to the floor of the cave and the signed junction between Upper and Lower. The data listed above for mileage and elevation gain exclude the lower cave, combining only the upper cave and the return trail. You may find that you hike more miles if you explore the Lower Cave as well.

Head into the Upper Cave. It's a 1.5 rugged miles one way, requiring significantly more time, caution, and some physical agility. It is a more interesting route though, with the lava tube shape, size, and geology changing frequently. Not far from the staircase, the passage encounters its first of many rock piles. You must climb up, over, or around the abrasive rocks, taking care not to twist an ankle or, in some places, bump your head.

At about 0.8 mile is the narrowest part of the passage, and the crux move: a slick, wet, 8-foot lava fall. Some people need assistance scaling it, as there is only one significant foothold.

Beyond the lava fall are a couple of rock formations that require some physical ability to climb over or to squeeze around. Then at about 1.2 miles is the Skylight, a hole in the ceiling which allows in the first natural light since the entrance. The Skylight is neither a safe nor legal exit.

The affixed metal ladder at about 1.4 miles is the Upper Entrance, and your exit. You may choose to continue the final 500 feet beyond to the natural end of the lava tube. The ceiling is only about 6 feet high in places, so take care. Then retrace your steps to the ladder and head up topside.

The return trail is marked for travel in snow. Simply follow the blue diamond markers affixed high on tree trunks. When snow not present, keep an eye out for other small caves and pockmarks in the rough lava. The trail drops gently the 1.3 miles back to the Main Entrance.

If the Upper Cave is a bit too rugged for you, consider exploring the Lower Cave. It's a broad lava tube that descends gently to its end. The floor is flat (though a bit uneven at first), then sandy later on, from a mud flow that filled the lower portion centuries ago. The end of the cave now is where the sand has filled in to within a couple feet of the ceiling. The Lower Cave is an easy walk, for a 1.5 mile round trip, that houses a popular geologic anomaly known as the Meatball.

Note: Some people hike the trail uphill, then enter the cave via the Upper Entrance. There are two concerns about this: Firstly, the lava fall is easier to ascend than to descend safely. Additionally, from the main entrance, you immediately experience climbing over and around rock piles, enabling you to decide whether the Upper Cave is more than you wish to attempt.

WTA Pro Tip: At 13,042 feet long (about 2.4 miles), Ape Cave is the third longest lava tube in North America. It is sometimes referred to as Ape Caves (plural) because the main entrance is between its two ends, referred to as the Lower Cave and Upper Cave.

Ape Cave was formed nearly 2000 years ago from lava streaming down the southern flank of Mount St. Helens. As the outer edges cooled into a hardened crust, the inner molten lava was able to drain away before it hardened, leaving behind a tube. After discovering the cave in approximately 1950, a logger told his spelunker friend. That friend explored the cave with his sons and their friends, who called themselves the Mount St. Helens Apes. Thus the name of the cave. poles are a big help for the knees. Depending upon the time of year, it is also possible to glissade down part of the mountain (but be cautious).




Driving Directions

From I-5 exit 21, travel north and east on State Route 503 (Lewis River Road). At 23 miles from the freeway, continue straight on Spur 503. At 31 miles, Spur 503 becomes Forest Road 90. Cross a bridge over a canal, then 2.6 miles later, turn left on FR 83. Travel 1.7 miles then turn left on FR 8303. Travel the final mile to the parking lot and Ape Headquarters Center. The parking lot has room for 50-60 vehicles, including bus and RV spots. There are vault toilets and garbage cans, but no drinking water. When it’s open, Ape Headquarters Center offers rental lanterns.

If the road is gated at the Trail of Two Forests junction (e.g. early in the season), you will have an additional half mile or so to walk, depending on how close you can park. A Sno-Park permit is required from December 1 through March 31, a Northwest Forest Parking Pass for the rest of the year.





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