Ape Cave is a lava tube located on the south side of Mount St. Helens volcano in Gifford Pinchot National Forest in Washington state. The cave was discovered in 1947 by Lawrence Johnson, a logger, when his truck fell into a sinkhole which opened into the cave. A Boy Scout troop under the leadership of Harry Reese performed the first exploration in 1950. They named the cave for their sponsor, the St. Helens Apes, a local group made up of mostly foresters.
Ape Cave, the third longest lava tube in North America, is a unique geologic environment since lava tubes are an unusual formation in this region: volcanoes of the Cascade Range are mostly stratovolcanos and do not typically erupt with pahoehoe (fluid basalt). Ape Cave is a popular hiking destination with moderate to difficult terrain. The lower cave is an easy trail to “Rail Road Tracks” and “Meatballs”. The upper cave is a more difficult hike with some narrow sections and climbing is required in certain segments. The upper cave trail leads to “The Big Room” (88ft width), “Lava Falls” (8ft height), and moss-covered skylight. Visitors to the cave need to be prepared for constant 42 degree F temperature, pitch black conditions and uneven and sometimes slippery surfaces.
Ape Cave History
Ape Cave formed about 2,000 years ago, but it wasn’t discovered until 1947 by a logger named Lawrence Johnson. In 1951, a local youth groupd led by Harry Reese extensively explored the cave. Leaving footprints where no one ever had, these lucky early explorers were able to travel through a pristine lava tube full of amazingly shaped and fragile formations.
The youth group dubbed themselves the St. Helens Apes, in memory of a 1924 hoax perpetrated by two boy scouts. The scouts decided to throw large, lightweight pumice rocks into a canyon. Unbeknownst to them, there was a cabin below with two miners inside. Seeing what looked like small ape like figures high up the canyon, making ape noises and hurling big rocks, the miners reported that apes attacked them. From this legend, Ape Cave received its name.
Ape Cave marks an unusual part of Mount St. Helen’s eruptive history. It was the only time in its 40,000 year existence the volcano erupted red, hot flowing lava, like Hawaii’s volcanoes. Eruptions of fluid lava, called basalt, are rare in the Cascade Mountain Range because magma rising below the Cascades have high silica content. The more silica in the magma, the less fluid it becomes. Thicker magma with suspended gases in it make eruptions much more explosive.
About 2,000 years ago, fluid basalt lava poured down the southern flank of the volcano and entered a stream channel. As the lava flowed, its surface cooled, creating a hardened crust. This crust insulated the molten lava beneath, allowing it to travel a great distance. The flowing lava beneath the crust melted and carried away rock and soil below it. This “thermal erosion” deepened and widened the channel, forming the cave walls. The level of lava in the tube rose and fell as the eruption surged and slowed. When flows stabilized for a period of time, lava built up on the walls, making ledges that reveal the depth of the flow. Hot fluid lava pulsed between the walls and ceiling for months, possibly up to a year, until the eruption subsided and lava drained from the tube. A spectacular 13,042ft (3976m) long lava tube, the third longest in the United States, was created as a result of this rare eruption.
Ape Cave Hiking Trail Map
Map – how to get to Ape Cave
Exact location of Ape Cave Lava Tube parking lot / trailhead is indicated by Green Arrow on the following map (click EXTERNAL LINK below to view map). From late June to early September, ranger-guided cave tours are available. Lantern can be leased out at a fee of US $5 plus tax at the ranger station of Ape Cave hiking trail head.
Lower Cave (Shorter and Easier Route)
From the main entrance the cave is divided into two sections. The 3/4 mile (1200m), one-hour round trip lower portion is easier to traverse. Interesting features include the meatball and railroad tracks.
The railroad tracks are the remnants of the collapsed walls of a miniature lava tube that formed inside the main tube.
The meatball is a round ball of lava that is actually a piece of breakdown that fell from the ceiling while lava was still flowing through the cave. It floated on the surface of the lava flow and was carried downstream until it got wedged in a narrow spot 12 feet (4m) above the floor.
The sandy floor found in the lower cave formed when volcanic ash, pumice, and other debris were washed into the cave flollowing an eruptive episode 450 years ago. Debris from this event causes the lower section to gradually narrow until the passage is completely blocked. Cavers must return to the main entrance to exit.
Upper Cave (longer and more difficult route)
The 1.5mi (2100m), upper portion is difficult to walk and young children are NOT recommended. Cavers must climb over 27 large breakdown boulder piles and scale an 8 foot (2.5m) high lava fall. there is a surface trail leading back to the parking lot—allow 3 hours round trip.
The rock piles, called breakdown, formed when the eruption subsided and lava drained out, leaving an empty tube. As the walls and ceiling cooled, they shrank, causing them to crack. Sometimes the cooling and cracking process weakened the walls and ceilings, causing them to collapse. The entrances to Ape Cave, called skylights, were in fact caused by breakdown.
other features include the 88 foot (27.5m) wide Big Room and a skylight in the floor where a small lava tube formed inside the Ape Cave tube. There are two skylights near the end of the upper section. Exit through the skylight with the ladder. Do not attempt to exit using the skylight without the ladder, serious injuries have occurred here.