Ape Caves Lava Tube at Mt St Helens

Let’s use our imaginations for a sec, okay? I’ll paint the scene: You’re engulfed in darkness and your eyes search desperately for something, anything, to cling to but they can’t. It’s pure darkness, unlike anything you’ve experienced before. And just when your heart starts to flutter with real fear, voices echo off the tunnel walls and the illusion is broken. You can’t help but laugh and flick on your light, illuminating the Ape Caves lava tube you’re exploring. Oh man, there’s nothing quite like adventuring in the depths of the earth to get your heart pounding!

Welcome to the Ape Caves lava tube at Mt St Helens.

You might also like to check out the Lava Canyon hike or Windy Ridge Viewpoint while you’re at Mt St Helens.

PS: This article contains affiliate links. I may earn a commission (at no cost to you) if you click them and/or buy a product; I only recommend products that I think will help you. Read my full disclosure statement here.

Trail Information

DifficultyLower Ape Caves: Easy
Upper Ape Caves: Moderate
LengthLower Ape Caves: 2.4 km, 1.5 mi
Upper Ape Caves: 5 km, 3.1 mi
Terrain StatsLower Ape Caves: Download PDF
Upper Ape Caves: Download PDF

Explore the Ape Cave Lava Tubes

Ape Caves lava tube is located in the Mt St Helens National Volcanic Monument in Washington state. It’s one of our favourite adventures in Washington and is a must-stop every time we visit Mt St Helens. Maybe it’s the nostalgia or maybe it’s because it feels like a tunnel to the center of the earth. Either way, we highly recommend the lava tube.

Fun fact: This lava tube is two-miles long. It’s thought to be the longest lava tube on the continental USA! C’mon, you know you want to explore it even more now.

Hiking in the dark Ape Cave lava tube at Mt St Helens
Girl explores in the very dark underground Ape Cave lava tube at Mt St Helens.
Man navigates boulders piles in the Upper Cave in the lava tube at Mt St Helens in Washington state.

Hiking at Ape Caves

Although there are no stalagmites, stalactites, and crystal clear pools in the lava tube, there are massive boulder piles and a slick lava fall to climb. They’ll test your adventurous side and it’s exhilarating! I’ve been in quite a few lava tubes and caves, and Ape Caves really does offer a unique experience.

Once you’ve gathered your lights, warm clothes, and sturdy shoes, it’s time to start exploring! There are two sections that you can hike: the Upper and Lower Caves. Each offers something unique to explore.


Regardless of which section you choose to explore, you’ll begin your adventure at Ape Headquarters which is a small building just off the parking lot. A fully paved trail leads to the Main Entrance and a staircase brings you to the tunnel floor. You’ll immediately notice the temperature drop.

When you reach the tunnel floor, the tube immediately branches into the Lower and Upper Caves. The Lower Cave, which is the easiest of the two sections, is the most obvious path and continues straight from the ladder. The Upper Cave, which is much more difficult, is accessed by ducking behind the stairs. It’s very easy to miss, so keep your eyes peeled.

During the summer, Park Rangers educate visitors about the lava tube at the top of the staircase. They talk about respecting the cave and the animals that live within (more info about that below).

The Main Entrance to Ape Caves lava tubes.
The staircase at entrance to the Mt St Helens lava tube.
Girl peaks out from the tiny, final chamber of the Lower Caves at Mt St Helens.

The Lower Ape Caves

The Lower Cave is a great way to ease yourself into exploring the lava tube. It’s an easy 1.5 mile (2.4 km) round trip that you can explore in about an hour. This section is also the best of the two for young kids or seniors.

It’s the most heavily trafficked of the two sections. Even though there are no built-in lights, this section is usually well lit because of the sheer amount of people exploring it.

What to Expect

At the beginning of the hike, the ground is a little uneven but it quickly transitions into a flat, sandy bottom. A mud flow swept through the Lower Cave centuries ago and left behind the sandy floor. The mud flow also blocked the end of the tunnel — if not for that mud flow, the tunnel would be much longer and rockier.

The Lower Cave is home two to impressive formations, the railroad tracks and the Meatball, as well as a tiny chamber. Despite being underground, the lava tube is broad and sweeping. In some sections, the ceiling soars to 30 feet!

I’ve always liked this part of the lava tube, but because it’s the easiest of the two sections you’ll never be alone. Lights flash and voices echo off the walls.

A map of the Lower Ape Cave.
Girl points to the Meatball rock formation in the Lower Ape Cave at Mt St Helens.
A man is dwarfed by a very tall section of the Lower Cave at Mt St Helens.

Railroad Tracks

The railroad tracks are a rock formation that runs along the side of the lava tube. It resembles, you guessed it, a railway track. The formation was created when lava drained from the tunnel and left behind minerals on the wall.

The Meatball

The Meatball is a ball of cooled lava that’s wedged between a narrow section of the lava tube. It’s perhaps the most well-known formation in Ape Caves. Back when lava flowed through the cave, the Meatball fell from the ceiling and was carried on the lava’s surface before it became wedged and hardened.

When you stand beneath the Meatball, it feels like it’ll fall at any moment! Don’ worry, though, it won’t. It’s been there for centuries. The Meatball is a pretty awesome volcanic formation that’s hard to miss.

Tiny Chamber

A tiny chamber marks the end of the Lower Cave. It’s only large enough to crouch in and has a very sandy floor. However, the airflow is very poor and often smells of ammonia which can be mistaken for urine.

To reach the chamber, you’ll crawl through a tiny tunnel on your stomach. The tunnel is only wide enough for one, maybe two people and isn’t even tall enough to crawl on all fours through. It can be both mentally and physically difficult to navigate, especially if you’re claustrophobic like I am. Luckily, though, you won’t have to crawl for too long.

It’s cool to say you’ve reached the chamber, but there’s not much to actually see. Of three times I’ve visited, I’ve only made it to the final chamber once.

Man crawls on stomach to reach the final chamber in the Lower Caves.
Man looks out from a tiny chamber in the lava tube.
The final chamber of the Lower Cave at Mt St Helens is very tiny and only large enough for one person.

The Upper Ape Cave

The Upper Cave is much more difficult than the Lower Cave. I want to stress that it’s not for everyone. You need to be physically able to climb over multiple large boulder piles and scale a slick, eight-foot tall lava wall in near darkness.

It’s a 1.5 miles (2.4 km) one-way hike and takes about 2.5 hours. The return trail is above ground and is very quick. Even though this section is the same length as the return Lower Cave trail, it takes over double the time to hike. It’s also much less popular and you’ll often explore the dark lava tube by yourself.

What to Expect

The formations in the Upper Cave are quite different than those in the Lower Cave. It’s full of caverns, large boulder piles, and even a slick lava fall.

There are two entrances to the Upper Cave: the Main Entrance and the Upper Entrance. The Main Entrance is the most common entry because it’s also the entrance to the Lower Cave. The Upper Entrance is located up the mountain and is also where the Upper Cave ends. If you start at the Main Entrance, the Upper Cave is accessed by ducking behind the bottom of the staircase. Few people will go this way and it’s easy to miss. You’ll be amazed at how quickly the noise and lights disappear.

When you’re alone, I highly recommend experiencing total darkness. It’s very eerie. You’ll become engulfed in a thick, eerie darkness with no sense of body. Your eyes will search desperately for any light. Even though you’ll stand in the darkness for only a few moments, it’s easy to imagine how people go mad in such stifling conditions.

Map of the Upper Cave at Ape Caves.
Sam and Jacob from Explore the Map selfie in a very dark lava tube.
A narrow, tall section of the lava tube.


Unlike the Lower Cave, the Upper Cave has a lot of variation in its size. Some sections are so large you won’t be able to see it all while other places are so narrow that you’ll feel the rock pressing in from every direction. While none of the areas are as small as the final chamber in the Lower Cave, they do require a certain agility to safely navigate.

The biggest cavern, aptly called The Big Room, is an 88-foot wide giant cavern and is located at the beginning of the Upper Cave. The ceiling is so tall you probably won’t see the top!

The "Big Room" in the Upper Cave at Mt St Helens is an 88-foot wide giant, underground cavern.

27 Boulder Piles

There are approximately twenty-seven boulder piles throughout the Upper Cave. You’ll have to climb over every single one and some are easier than others. Even though the piles may look delicate, just remember that they’ve lain that way for hundreds of years.

The rock piles were formed when the volcanic eruption that created the Ape Cave ended and lava drained from the tube. As the lava cooled, it shrank and cracked. The cracks weakened the walls which caused parts of them to collapse. These collapses formed the large rubble piles and the entrances to the lava tube. The rock piles are full of sharp lava rock, loose rubble, and large holes. Make sure to watch your step and ensure the rocks are stable before walking on them.

8-Foot Lava Fall

About 0.8 miles (1.3 km) into the hike is the most difficult section of the Upper Cave: an eight-foot lava fall. It appears out of nowhere and looks pretty intimidating. When we came upon it, we thought we’d gone the wrong way (sadly, we don’t have a picture because we were too concerned about climbing the fall).

The lava fall is slick and there’s only one significant foothold to assist in the climb. Sometimes there’s a rope, but it’s quite dangerous to use and the Park Rangers regularly remove it. If you’re not hiking in a large group, you’ll likely need strangers to help boost you up.

At the top of the lava fall, the tunnel quickly siphons you into a tiny passage full of rock formations. It can be awkward to navigate because you’ll need to either climb over or squeeze around them.

Hiking in the lava tubes at Mt St Helens in the summer.
A large boulder pile in the Upper Cave that fell hundreds of years ago after one of Mt St Helens eruptions.
Woman stands on top of one of 27 large boulder piles in a dark lava tube.

Exit + Return Trail

There are a few more rock piles after the lava fall, but after scaling the lava fall you’ll probably find them pretty easy. About 1.2 miles (1.9 km) into the hike, there’s a skylight. It’s the first sign of above ground since beginning your adventure. After hiking in the darkness for hours, the light from the skylight is blinding and the foliage is very vibrant. Despite how tempting it is to leave here, exiting at the skylight is neither legal nor safe.

Only a short walk from the skylight is the exit, which is also known as the Upper Entrance. A permanently attached metal ladder quickly and easily brings you to the surface. When you exit, the light is overwhelming and the heat above ground (especially in the summer) can be stifling. The exit is nothing more than a small hole in the ground that can be hard to notice.

A well-marked path will bring you back to the Main Entrance. You’ll pass beside small lava tubes and sinkholes that are fun to explore. You’ll even enjoy a clear view of Mt St Helens in the distance!

A metal ladder at the exit of the Upper Caves at Mt St Helens, Washington.
Women looks down at a small hole, which is the entrance to the lava tubes.
A large boulder pile in the Upper Cave lava tubes.


Mt St Helens is most commonly known for her violent eruption in 1980. However, the volcano has actually been active for roughly 40,000 years. In that time, she’s seen and created a lot of things!


About 2,000 years ago, the Ape Caves lava tube was formed.

Way back in about 0 CE, fluid lava poured from Mt St Helens’ southern side — similar to the Hawaiian volcanoes today. When the outer edges of lava cooled, an insulated crust formed which allowed the inner lava to continue flowing. The fast-moving inner lava pulsed through the tunnel for months and slowly created the lava tube we can explore today.


In 1947, the lava tube was discovered by Lawrence Johnson, a local logger. He noticed a tree growing at a strange angle and after investigating it, he found a large sinkhole. The sinkhole opened into a large, dark tunnel where an overhang and echoing cavern lay. He was unable to continue investigating on his own, so he came back later with his crew. However, no one wanted to lower themselves into the dark hole — surprising, right? Who wouldn’t want to do that? — so Johnson contacted a local spelunker and scout leader, Harry Reese, to investigate.

Reese and his scouts were the first to explore the pristine lava tube in the early 1950’s. They extensively explored the cave yet never found evidence of previous human exploration. Pretty cool, eh?

Why is it Called Ape Caves?

You can thank those adventurous scouts for the lava tube’s name! The scouts named the lava tube in honour of their sponsor, the St Helens Apes.

However, there’s some controversy around the name. Some people have reported seeing and encountering Bigfoot roaming the area. They believe the lava tube was named after the large, ape-like creature and not the scouts. Likely story? I’ll let you decide.

Hiking over a large rock pile in the Upper Ape Caves.
Girl climbs over a large boulder pile in a dark lava tube.
Man enters a small tunnel in the Lower Caves lava tube.


I’d be amiss if I sent you exploring the lava tube without providing some safety info first. I’m all about keeping you safe! In addition to the below tips, it never hurts to bring the ten essentials on your hikes, too.

Flashlights + Lanterns

First things first, there’s no light source in the lava tube. You’re 100% responsible for bringing your own light.

It’s extremely dangerous to explore the cave without proper light because there are many obstacles like boulder piles, low ceilings, and sharp rocks. We recommend having two to three strong light sources per person for maximum safety — and no, your phone’s flashlight doesn’t count.

Lanterns are one of the best light sources available because the volcanic walls don’t adsorb their light well. You can rent them at the Ape Headquarters in the summer for about $5.

Natural Obstacles

There are many large, jagged boulder piles — particularly in the Upper Cave — that fell from the ceiling long ago and they can be quite difficult to navigate.

You absolutely need sturdy footwear. Do not wear sandals. I repeat, don’t wear sandals. A twisted ankle, or worse, could easily make your exploration of the lava tube very unpleasant.

If you’re planning on exploring the Upper Cave, only do it if you’re physically able to navigate large piles of fallen boulders with little light. This is an important time to be real with yourself about your hiking abilities and to choose a trail that’s right for you.

Hiking in a large, cavernous section of the Ape Caves lava tube at Mt St Helens.
A piece of volcanic rock in the lava tube.
Checking out the railroad tracks rock formations in lava tube at Mt St Helens.

Respecting the Lava Tube

As you explore Ape Caves, remember to help protect it by being a respectful visitor. By doing our part, the cave will stay beautiful for years to come and future generations will be able to explore it.

Cave Slime

The lava tube is home to many living creatures, most of which are too small to see. The cave walls are covered in a white algae that’s commonly known as “cave slime”. This slime is extremely important to the cave’s health because it feeds small animals.

However, when you touch the algea it dies and takes many years to regrow. Unfortunately, people have written on the walls which has killed a lot of the fragile organism. When you’re in the lava tube, try very hard to not touch the walls.

White-Nose Syndrome + Bats

Small-eared bats also live in the lava tube. They rarely bother visitors, but they’re very susceptible to disease people may carry. The most devastating disease is white-nose syndrome because it’s lethal to them. As of April 2016, the disease has killed 6 million small-eared bats in Canada and the USA.

Ape Cave is currently free of the disease, but when a cave becomes infected it spreads like wildfire. If one bat is infected, within two years about 90% of its colony will be dead. Because of this, Park Rangers work relentlessly in the summer to educate visitors.

Protecting the small-eared bats is an ongoing process, but one of the easiest things you can do is ensure you don’t wear clothes in the lava tube that you’ve worn in other caves. To learn more about white-nose syndrome and what you can do, check out WhiteNoseSyndrome.org.

Leave No Trace

When you hike the lava tube, it’s important to leave no sign that you were there. Remember to bring only yourself, warm clothes, and lights. Always leave your food, drinks, e-cigs, and pets at home; smoking, fires, rock collecting, and littering is prohibited.  You can learn more about leave no trace practices in hiking etiquette article

As the old saying goes, “take nothing but pictures, leave nothing but footprints, kill nothing but time”.

Mt St Helens peeks out through some trees in the distance.
A women explore a small, collapsed sinkhole on the path back to the Ape Headquarters.
A sparse forest on the trail between the Upper Entrance and Ape Headquarters.

Packing Suggestions

Ape Cave is a rugged natural lava tube. It’s had little human interference over the years and because of this, it’s important to be prepared.

The most important thing to bring on your adventure are two to three strong light sources — we recommend both headlamps and handheld flashlights. Your phone’s flashlight doesn’t count. It’s also always a little chilly inside the lava tube, so warm clothing like base layers, vests, or sweaters are great. I also recommend wearing a backpack with a water reservoir because you’ll want your hands free as much as possible. And last but certainly not least, you need to wear sturdy hiking shoes.

The Ape Caves sign at Mt St Helens.

Final Notes


Ape Caves is free! Before you get super excited, though… it’s free to enter the lava tube, but you do have to buy a parking permit. From April 1 to November 30, you’ll need the Northwest Forest Pass, which is $5 for one day or $30 for a season. From December 1 to March 31, you’ll need the Sno-Park Permit (which you’ll need to buy ahead of time because it isn’t available on-site).

You can also rent lanterns in the summer for about $5 from Ape Headquarters.

PS: If you’re interested in taking an all-day, small group tour of Ape Caves and area, Viator has a great tour!

Open Dates + Parking

Luckily for you, Ape Caves lava tube is open year-round! It’s a perfect adventure for every season. Don’t be scared to visit in the winter. Just know that in the winter the parking lot, Ape Headquarters, and lantern rentals are all closed.

There’s a large parking lot at Ape Headquarters that has room for buses, RVs, and regular cars. In the summer the parking lot fills up quite quickly, but luckily there’s more parking available along the road. In the winter, the parking lot is closed. You’ll have to walk or snowshoe in from the Trail of Two Forests which is just over 0.8 mile (1 km) away.

Exploring the tiny chamber at the end of the Lower Ape Cave at the Mt St Helens lava tube.


The temperature inside Ape Cave lava tube rests at about 40°F (5°C) all year long. Water drips from the ceiling, so it’s important to dress for the cool weather even when it’s sweltering above-ground. You’ll also sometimes experience cold breezes in narrow sections of the cave which can temporarily make it even colder.

Ape Headquarters

The Ape Headquarters is a US Forest Service building near the lava tube’s entrance. In the summer you can rent lanterns, buy souvenirs, and enjoy guided walks from here. Vault toilets and garbage disposal are also available here, but there’s no drinking water.

The Headquarters are closed in the winter. It opens for weekends in May and in mid-June opens seven days a week for the summer.


Ape Caves is located to the south of Mt St Helens near the town of Cougar, Washington.

To get here, drive on NF-90 (Lewis River Road) and turn onto NF-83. Stay at NF-83 for 1.7 miles (2.7 km). You’ll begin to see signs for Ape Caves; turn left onto NF-8303 and then travel the final mile to Ape Headquarters and the trail head.

PS: Don’t forget to check out Windy Ridge Viewpoint and the Lava Canyon hike while you’re at Mt St Helens!

Similar Posts