With a total length of more than 2 miles, Ape Cave is the longest lava tube in the continental United States. Located on the south side of Mount St. Helens, the site offers routes through both the upper and lower tubes of Ape Cave. Both tubes remain a constant 42 degrees throughout the year.
You will find an ample amount of informational and educational signs at the trailhead, at the mouth of the cave, and along the forest trail, all of which directs you to the cave of your choosing and back to your car. The easier of the two choices, the lower tube, is less than a mile long and can be hiked down and back in approximately one hour. The upper Ape Cave is 1.5 miles long and will take more than two hours to complete, which includes returning to the parking lot via an above-ground trail. The upper tube is clearly a more adventurous route, as this section of the cave requires scrambles over a number of boulder piles and ducking through some tight passages. No matter what the weather conditions are outside, the caves will always be a damp-and-dark 42 degrees, so be sure to bring warm clothing as well as a headlamp and/or flashlight with backup batteries.
The Ape Cave attraction is open year round, although winter access will require a hike in with snowshoes and an extra trek added to the 2-mile trip. Because of the snow levels, the roads in the winter are not plowed all the way to the Ape Cave Trailhead. Parking in the winter is at the Trail of Two Forests Interpretive site, which will tack and extra 0.8 miles from your car to the trailhead, each way. Even with the extra travel, the adventure is barely more than 3.5 miles round trip and is well worth the effort. It's not every day that you can snowshoe around on a recently erupted volcano and then descend into what will likely be the largest cave you've ever explored.
Winter backcountry adventures can be dangerous outdoor activities that pose significant risks as conditions affecting safety (i.e. weather, snowpack stability, avalanche hazard) are constantly changing. Prior to engaging in these activities each individual should get the proper training to make safe decisions and be equipped to use avalanche safety resources and tools. Please visit our Backcountry Skiing and Avalanche Safety post to learn more.