Engulfed in darkness with tonnes of hardened lava pressing down from above, we lost all sense of direction. Our eyes searched desperately for something to cling to, but the darkness was overwhelming. I raised my hand and brought it to my nose, unaware of where it was in relation to my face. Just as our hearts started to flutter with fear of the unknown, voices began to echo off the tunnel walls. I let out a sigh, equal parts relief and disappointment; our end-of-the-earth illusion was effectively shattered. With a laugh, we flicked on our flashlights and lit up the cavern. This particular cavern was small, only a tiny taste of the two-mile long Ape Cave lava tube at Mt St Helens we were exploring. We continued on, excited to unlock Ape Cave’s secrets. There’s nothing quite like exploring tunnels in the depths of the earth.

History of Ape Cave

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 actually been active for roughly 40,000 years.

Her eruptions are often violent, pyroclastic flows that shoot hot gas into the air. However, 2,000 years ago fluid basaltic lava poured from her southern side, much like the Hawaiian volcanoes. 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 we 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 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 investigated it, where he found a large sinkhole. The sinkhole opened into a large, dark tunnel where an overhang and echoing cavern lay. Unable to continue on his own, he later brought 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.

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

Ape Cave, Mt St Helens

Ape Cave is one of our favourite adventures, 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. With no man-made infrastructure except for the entrances, 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 our skill – and it’s exhilarating!

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.

Accessing the lava tube

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! The Upper and Lower caves 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 to the side of the stairs and continuing behind them.

Preparing yourself for the Ape Cave lava tube

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 drips water, so it’s important to dress for the cool weather, even when it’s sweltering above-ground. It’s common to experience cold breezes in narrow sections of the cave, which will drop the temperature even further.

Staying safe in the lava tube

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. As such, sturdy footwear is absolutely necessary. A twisted ankle, or worse, would make your exploration of Ape Cave very unenjoyable.

There are absolutely no light sources in the cave, so you must provide your own light. It’s extremely dangerous to explore the cave without proper light because there are many obstacles, such as the aforementioned boulder piles, low ceilings, and sharp rocks. It’s recommended to have 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*.

*Pricing as of 2016

Adventuring in 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. As such, it’s usually well lit. In the beginning, the ground is a bit uneven but it quickly transitions into a flat, sandy bottom. Centuries ago a mud flow swept through the Lower Ape Cave; it left behind the sandy floors and blocked the end of the tunnel. I desperately wish we could explore beyond the blocked tunnel!

Despite being underground, the lava tube is broad and sweeping; the ceiling often soars to 30 feet, even in the narrow sections! The Lower Ape Cave is home two to impressive formations: the railroad tracks and the Meatball.

Formations in the Lower Ape Cave

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, 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. As I stood beneath it, I was sure the Meatball would fall at any moment! It’s an amazing formation that’s hard to miss.

Exploring a tiny chamber

The Lower Ape Cave ends in a tiny chamber that requires crawling through a tiny tunnel, so low that you’re reduced to sliding on your stomach. The tunnel is only wide enough for one and has brought out my claustrophobia on more than one occasion. 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).

I’ve always liked the Lower Ape Cave, particularly the challenge of the final chamber, but it’s not nearly as exciting as the Upper Ape Cave. Because it’s the easiest of the two sections, we were never alone; lights constantly flashed and voices echoed off the walls, which felt more like a night trip to an amusement park than a tunnel in the wild. The Upper Ape Cave though, that’s where the true adventure begins!

Spelunking in the Upper Ape Cave

There are two entrances to the Upper Ape Cave and the most common is the Main Entrance near the trailhead. The second requires hiking to the Upper Entrance. We’ve always started at the Main Entrance, but either entrance gives you an amazing experience. The Upper Cave is 1.5 miles of difficult hiking and takes about 2.5 hours. Sturdy shoes and good lighting are a must.

The Upper Cave is accessed by ducking beside the final ladder at the Main Entrance. As we left the ladder behind, we were amazed at how quickly the noise and lights disappeared. We were suddenly alone, an event we hadn’t yet experienced in Ape Cave, so we decided to experience total darkness. We stood close to one another and flicked off our lights. The walls devoured the light and we were engulfed in an eerie, thick darkness. With no sense of body, our eyes searched desperately for the light they craved. We stood in this darkness for only a few moments, but in those moments it was easy to imagine how people go mad in such stifling conditions.

Formations in the Upper Ape Cave

The Big Room, an 88-foot wide giant cavern, is located at the beginning of the Upper Cave. The ceiling expands high into the darkness, so high that our flashlights could barely reach it.

There are approximately 27 boulder piles throughout the Upper Cave, ranging in difficulty. 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.

Unlike the Lower Ape Cave, the Upper Cave greatly varies 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 on the Lower Cave, they do require some agility to navigate safely.

Scaling an 8-foot lava fall

About 0.8 miles into the hike is the smallest, and arguably the most difficult, section of the Lower Cave. The 8-foot lava fall appears as if out of nowhere and is quite slick, with 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. Often strangers will help one another up. The tunnel at the top is fairly small and quickly siphons into a tiny passage full of rock formations that require climbing over or squeezing around.

There are a few more rock piles after the lava fall, but after scaling the slick rock they are quite easy. At about the 1.2-mile marker there’s a skylight, the first sign of above ground since beginning the adventure. After hiking in the darkness for hours, the light from the Skylight is blinding and the foliage vibrant. Despite how tempting it is to leave here, exiting at the Skylight is neither legal nor safe.

Exiting the Upper Ape Cave

Only a short walk from the Skylight is the exit, the Upper Entrance. There is a permanently attached metal ladder here that quickly 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. The path passes beside small lava tubes and sinkholes, which are fun to explore. It soon enters the shade of a forest before passing by a ridge of lava with a clear view of Mt St Helens in the distance. It reenters the forest and 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.

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 writing on the walls has killed large amounts of this fragile organism.

White-Nose Syndrome and 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. As such, 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 WhiteNoseSyndrome.org.

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. 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:


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.


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.

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.

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
Pricing It’s free to enter the lava tube, but you must pay for a parking permit.

  • Bring two to three sources of light
  • Wear warm clothing, even in summer
  • Wear sturdy shoes
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