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Easy Hike, Moderate Hike, Washington

Ape Cave Lava Tube at Mt St Helens 

Imagine being engulfed in darkness with tonnes of hardened lava pressing down from above and losing all sense of direction. Your eyes search desperately for something to cling to but the darkness is overwhelming. You raise your hand and bring it to your nose but have no idea where it actually is. Just as your heart starts to flutter with fear of the unknown, voices echo off the tunnel walls. You let out a sigh and with a laugh, you flick on your flashlight and light up the cavern. This particular cavern is small, only a tiny taste of the two-mile-long Ape Cave lava tube at Mt St Helens you are exploring. You continue on, excited to unlock all of Ape Cave’s secrets. There’s nothing quite like exploring tunnels in the depths of the earth to get your heart pounding with excitement.

History of Ape Cave at Mt St Helens

Ape Cave lava tube is located in the Mt St Helens National Volcanic Monument in Washington state. Mt St Helens is most commonly known for her violent eruption in 1980, but the volcano has been active for roughly 40,000 years and created Ape Cave about 2,000 years ago.

Formation of Ape Cave

Roughly 2,000 years ago, fluid basaltic lava poured from Mt St Helens’ southern side, much like the Hawaiian volcanoes today. As the outer edges of this lava stream cooled, an insulated crust formed which allowed the inner lava to continue flowing. This fast-moving inner lava, which pulsed through the tube for months, created one channel which is the lava tube you can explore today.

The two-mile long lava tube is thought to be the longest on the continental USA and offers two paths to explore, the Upper and Lower cave.

Discovery of Ape Cave

Around 1947, a local logger named Lawrence Johnson discovered Ape Cave. 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 on his own, so he returned with the rest of his crew to investigate. However, no one wanted to lower themselves into the dark hole so he contacted Harry Reese, a local spelunker and scout leader, to investigate instead.

In the early 1950’s, Reese and his scouts were the first to explore the pristine lava tube. They extensively explored the cave and never found evidence of previous human exploration. The scouts named the cave in honour of their sponsor, the St Helens Apes.

There have also been accounts of “Bigfoot” roaming the area. Some people believe the lava tube was named after the large, ape-like creature instead of the scouts.

Explore Ape Cave at Mt St Helens

Ape Cave is one of our favourite adventures and is a must-stop every time we make it down to Mt St Helens. While other caves have more things to see like giant stalagmites, stalactites, and crystal clear pools, this lava tube is simply a great adventure. There is no man-made infrastructure in the cave except for the entrances, so Ape Cave feels like a tunnel to the center of the earth. Climbing the massive boulder piles and scaling the slick lava wall truly test your skill – and it’s exhilarating!

Ape Cave lava tube is open year-round and is a perfect adventure for every season. However, in the winter the parking lot, Ape Headquarters, and lantern rentals are all closed. The cave rests at about 5°C (40°F) all year and water drips from the ceiling, so it’s important to dress for the cool weather even when it’s sweltering above-ground. You’ll sometimes experience cold breezes in narrow sections of the cave which will temporarily make it even colder.

The parking lot is quite large, but during the summer it’s almost impossible to find parking. Luckily, additional roadside parking is available down the road. In the winter, the parking lot is gated and snowed in. Instead, park at the Trail of Two Forests and snowshoe in. The Northwest Forest Pass is required to park in the summer and the Sno-Park Permit in the winter. The Ape Headquarters, where you can buy souvenirs and rent lanterns in the summer, is located just off the parking lot. Washrooms are also available here.

Staying Safe in the Lava Tube

There are no light sources in the cave and you need to provide your own light. It’s extremely dangerous to explore the cave without proper light because there are many obstacles, such as boulder piles, low ceilings, and sharp rocks. We recommend having two to three strong light sources per person for maximum safety (no, your phone doesn't count). Lanterns are one of the best light sources available because the volcanic walls have a harder time absorbing their light than flashlights. Lanterns are available for rent in the summer at the Ape Headquarters for about $5*.

There are many large, jagged boulder piles (particularly in the Upper Cave) that have fallen from the ceiling long ago that can be quite difficult to traverse. Sturdy footwear is absolutely necessary. A twisted ankle, or worse, would make your exploration of Ape Cave very unenjoyable. You should only explore the Upper Cave if you’re physically able to navigate large piles of fallen boulders with little light.

*Pricing as of 2016

Begin Your Adventure in Ape Cave

A fully paved trail leads from the Ape Headquarters to the Main Entrance, which is the location of the large sinkhole Lawrence Johnson found in the mid-1900s. During the summer, Park Rangers educate people about the lava tube. Ape Cave is accessed by two sets of stairs at the Main Entrance; the first leads into the sinkhole and a few yards further the second stairway drops 18 feet into the main tube. The immediate drop in temperature is astounding!

There are two sections of the lava tube, the Upper and Lower Caves, that branch off immediately upon reaching the tunnel floor. The Lower Cave, the easiest of the two sections, is the most obvious and continues straight from the ladder. The Upper Cave requires ducking behind the stairs.

The Lower Ape Cave

The Lower Ape Cave is an easy 1.5-mile round trip that can be explored in about an hour. This section is the most heavily trafficked and is popular with families with young kids. Even though there are no built-in lights, this section is usually well lit due to the sheer amount of people exploring it.

In the beginning, the ground is a bit uneven but it quickly transitions into a flat, sandy bottom. Centuries ago a mudflow swept through the Lower Ape Cave and it left behind sandy floors and blocked the end of the tunnel. Despite being underground, the lava tube is broad and sweeping and the ceiling often soars to 30 feet, even in the narrow sections!

What to Expect from the Lower Ape Cave

The Lower Ape Cave is home two to impressive formations, the railroad tracks and the Meatball, as well as a tiny chamber. I’ve always liked the Lower Ape Cave, particularly the challenge of the final chamber, but because it’s the easiest of the two sections, you’ll never be alone; lights will always flash and voices echo off the walls.

Railroad Tracks

The railroad tracks are a formation of rock that runs along the side of the tunnel that resembles a track. They were formed as the lava drained and minerals along the side were left behind, trailing after the retreating lava flow.

The Meatball

The Meatball, which is arguably the most well-known formation in Ape Cave, is a ball of cooled lava that fell from the ceiling while lava flowed through the cave. It was carried on the surface of the lava before it became wedged in a narrow section and hardened. When you stand beneath it, it feels like it’ll fall at any moment! It’s an amazing formation that’s hard to miss.

Tiny Chamber

The Lower Ape Cave ends in a tiny chamber where the rest of the lava tube has been blocked by sand. To reach the chamber, you have to crawl through a tiny tunnel on your stomach. The tunnel is only wide enough for one and is both mentally and physically difficult to crawl through, especially if you’re claustrophobic. The final chamber is only large enough to crouch in and has a sandy floor; however, the airflow is very poor and often smells of ammonia (which can be mistaken for urine).

The Upper Ape Cave

There are two entrances to the Upper Ape Cave: the Main Entrance and the Upper Entrance. The most popular is the Main Entrance because it’s also the entrance to the Lower Ape Cave. To reach the Upper Entrance, you’ll have to hike up the mountain. The Upper Cave is 1.5 miles of difficult hiking and takes about 2.5 hours. Sturdy shoes and strong lights are a must.

If you start at the Main Entrance, the Upper Cave is accessed by ducking beside the last ladder. As you leave the ladder behind, you’ll be amazed at how quickly the noise and lights disappear. You’ll suddenly be alone and it’s a great time to experience total darkness. Stand close together and flick off your lights. The walls devour the light and you’ll become engulfed in a thick, eerie darkness. You’ll have no sense of body and your eyes will search desperately for the light they crave. 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.

What to Expect from the Upper Ape Cave

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


Unlike the Lower Ape Cave, the Upper Cave varies greatly in size. Some sections are so large you won’t be able to take it all in while other places are so narrow that you’ll feel the rocks 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 expands high into the darkness and it’s so tall that your flashlight will likely have trouble reaching the ceiling.

Boulder Piles

There are approximately 27 boulder piles throughout the Upper Cave, ranging in difficulty, that you’ll have to climb over. Despite how menacing the piles look, they have lain that way for hundreds of years. They were formed when the eruption that created the Ape Cave waned and the 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.

Lava Fall

About 0.8 miles into the hike is the smallest, and arguably the most difficult, section of the Lower Cave: 8-foot lava fall. It appears out of nowhere and looks quite daunting, especially knowing that you’ll have to climb it. The fall is quite slick and there’s only one significant foothold to assist in the climb. Sometimes a rope is present, but it’s quite dangerous to use and Rangers regularly remove it. If you’re not hiking in a large group, you’ll likely need the help of strangers to boost you up. The tunnel at the top is small and quickly siphons into a tiny passage full of rock formations that require climbing over or squeezing around.

Exiting the Upper Ape Cave

There are a few more rock piles after the lava fall, but after scaling the slick rock they’re quite easy. At about the 1.2-mile marker there’s a skylight which is 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, the Upper Entrance. There is a permanently attached metal ladder here that quickly and easily leads to the surface.

Upon exiting, the light is overwhelming and takes some adjusting to get used to. After the coolness of the lava tube, the heat above ground (in the summer) is stifling. A well-marked path leads back to the Main Entrance. You’ll pass beside small lava tubes and sinkholes that are fun to explore. You’ll soon enter the shade of a forest before passing by a ridge of lava with a clear view of Mt St Helens in the distance. After reentering the forest, you’ll pass over two creeks (which are usually dry in the summer), before meeting up with the Main Entrance.

Respect Your Surroundings

As you explore Ape Cave, help protect it by being a respectful visitor. By doing our part, the cave will stay beautiful for years to come and let future generations 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 white algae, commonly known as “cave slime”, that’s extremely important to the cave’s health. It acts as food for fungus fly larvae, which in turn are eaten by small bugs. However, when the algae are touched it dies and takes many years to regrow. Unfortunately, people have written on the walls which have killed large amounts of this fragile organism.

White-Nose Syndrome & Bats

Small-eared bats also live in Ape Cave. They rarely bother visitors, but they are very susceptible to disease people may carry. The most devastating disease is white-nose syndrome which is lethal to them. As of April 2016, the disease had killed 6 million small-eared bats in Canada and the USA. Ape Cave is currently free of the disease, but once 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 you’ve worn in other caves. To learn more about white-nose syndrome and what you can do, visit

Leave No Trace

While exploring Ape Cave, it's important to leave no sign that you were there. Bring only yourself, warm clothes, and lights. Leave your food, drinks, e-cigs, and pets at home; smoking, fires, rock collecting, and littering is prohibited.  We talk a little more about Leave No Trace in our hiking etiquette article

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

Recommended Gear

Ape Cave is a rugged natural cave with little human interference. As such, it’s important to be prepared when you enter the lava tube. You’ll need two to three strong light sources, warm clothing, and sturdy shoes.

From experience, we know that having a headlamp and a flashlight with high lumens make all the difference. There’s nothing worse than trying to navigate through a dark tunnel without ample light! A headlamp is crucial as it allows you full use of both your hands, which is especially important in the Upper Ape Cave as you scramble over the many rock piles. A handheld flashlight is great for the flat sections and for safely inspecting the walls and ceiling of the lava tube, which are actually quite colourful! We like the following products:

Recommended: Flashlight

This flashlight has more than enough power to bring you safely through Ape Cave. It has multiple settings for brightness, which lets you easily adjust for the large rooms and tiny chambers. It’s small enough to fit in your pocket when traversing particularly difficult sections.

Recommended: Headlamp

Headlamps are a lifesaver when you’re exploring dark caves, particularly when you’re climbing over the large rock piles in Upper Ape Cave. This headlamp has multiple brightness settings which allow you to adjust based on the size of the cavern you’re in.

Recommended: Sturdy Shoes

No matter which section of Ape Cave you decide to explore, it's important to have sturdy shoes to avoid injury. While we strongly recommend hiking shoes, we’ve only ever worn simple runners while exploring the lava tube.

Directions & Trailhead Location

From NF-90 (Lewis River Road), turn onto NF-83 and travel for 1.7 miles. Turn left (there are signs for Ape Cave) onto NF-8303 and then travel the final mile to the parking lot and Ape Headquarters.

The parking lot is quite large and has enough room for buses and RVs. Vault toilets and garbage disposal are available here, but no drinking water. In the summer months, Ape Headquarters offers lantern rentals. If the gates are closed in the winter, you can park at the Trail of Two Forests and hike about a mile in.

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

Distance• Lower Ape Cave: ~1.5 mi (2.5km) round trip
• Upper Ape Cave: ~3 mi (4.8km) round trip
• Total: ~4.5mi (7.2km)
Duration• Lower Ape Cave: ~1hr
• Upper Ape Cave: ~2.5hr
Difficulty• Lower Ape Cave: Easy
• Upper Ape Cave: Moderately difficult
PricingIt’s free to enter the lava tube, but you must pay for a parking permit.
• April 1 to November 30: Northwest Forest Pass
• December 1 to March 31: Sno-Park Permit
 Notes• Bring two to three sources of light
• Wear warm clothing, even in summer
• Wear sturdy shoes

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