When we went camping last month, we decided to check out an area of Mount St. Helens we hadn't yet explored: Ape Cave Lava Tube.
At over two miles long, Ape Cave Lava Tube is considered the longest lava tube in the continental United States. What is a lava tube? Basically, as lava flowed long ago, the outer portion of the lava cooled and hardened creating tubes through which fluid lava continued to flow. The fluid lava drained away, leaving the empty tube behind.
If you like caving, Ape Cave is for you. The cave is long, and dark, and big, and did I mention dark?
Not a lot of photos here because... dark. But the kids had a blast exploring this huge tube. We just let the kids freely hike about while wearing headlamps and holding flashlights or lanterns.
A word of caution; the stairs and ladders can get a little slick, so I encourage the use of railings. Also, if you don't do well on uneven ground or in the dark, this activity if probably not for you. And keep in mind that if you go the whole two miles, you still have to get back. We didn't really think about that going into our explorations and we ended up with a couple of overly tired kids by the time we came out.
Fees: During the summer, a Northwest Forest Parking Pass is required - $5/day, $30/season
What to bring: Warm clothes, flashlights, water, a snack
Length of hike: Over 2 miles, one direction