Ape Cave: Ancient Lava Tubes, a Winter Wonderland

Upper Ape Cave exit in winterIt’s December and I really want to go for a hike. I want that feeling that being surrounded by nature and being outside give you. Unfortunately for me, the weather has not been good here in Portland, but I’ve never been one to stay in because of a little rain. There are very few places a true Pacific Northwest hiker can’t go if they have the equipment, but when there is nasty weather and it’s cold outside, I find caves to be the perfect answer.

Caves, by nature, have special qualities about them. Most have constant temperatures that don’t change even when it’s cold or hot outside. Many caves are created by water; have geological formations of crystals, stalagmites, or stalactites in them; and are homes to millions of creatures like the bat, olm, and cave crayfish to name a few (LEARN MORE). This is where Ape Cave, in Gifford Pinchot National Forest just South of Mount St. Helens in Washington, is unique. Yes, it has a constant temperature of 42 degrees year-round. Yes, it has some stalagmites and stalactites forming, too, but because of regular human disturbances this cave is no longer home to local bat populations. The most abundant living thing in Ape Cave is “cave slime”.

Ape Cave Shape, hiker glowThis cave is home to many living creatures. “Cave slime” is an algae-bacteria that grows on the walls and ceiling. If you touch it in any way, it will die. Cave slime plays an important role in the cave. It is food for fungus fly larvae. The fly larvae are eaten by small predatory bugs, known as grylloblatids. You may see a shimmering when you shine your light on the cave walls. It is the cave slime having lunch on the reflective water beads! [link]

Lava flow formationsApe Cave was formed by the volcanic actions and underground lava flows of Mt. St. Helens. It’s what scientists call a lava tube. Lava tubes are a type of lava cave formed when active lava flows develop a continuous and hard crust, which thickens and forms a roof  and walls around the still-flowing lava. These types of caves form in two ways: by the crusting over of lava channels, and from pahoehoe flows where the lava is moving underground.

Lava Falls at Ape Cave

As the longest continuous lava tube in the continental United States, it is at least 13,042 feet (3,975 m) long. That’s just under 2.5 miles long. The tube itself is fairly straight and for the most part is large and roomy throughout. There are two options when you arrive on the cave floor: the easy .75 mile path to the deeper levels of the cave, and the “difficult” 1.6 mile section that slowly rises closer to the surface as you travel up the tube. The “difficult” section is pretty rough terrain. You will need to scramble over large piles of fallen ceiling debris and tall lava falls, the tallest reaching just over eight feet high.

mt-st-helens-bigfoot-print_tnWhat was most intriguing to me was the story behind the cave’s name. I originally thought the cave was named because of the abundant “big foot” sightings noted in the area, but in fact it was named for the local Boy Scout troop who called themselves the Mt. St. Helens Apes. The Apes were the first group to explore the caves, but not the first on record for its discovery. That honor goes to Lawrence Johnson, a logger, who noticed strange sink holes and found what is today’s main entrance to the cave more than 65 years ago.

Meatball formationMost caves have intense cave formations, but that really isn’t what Ape Cave is most famous for. The only striking formation other than the shapes of the lava flow surface and the opening in the ceiling is “Meatball” – a block of cooled lava which broke free from the lava tube ceiling while hot lava was flowing below. It was carried along by the lava until it became wedged in a narrow spot above the cave trail.

The cave’s constant 42 degree temperature means that cave explorers should dress warm, have strong-soled hiking shoes that can grip the rough lava, and should come equipped with a head lamp or lantern for exploring. Hiking shoes with good ankle support, durable gloves and a whistle are a few extras that I recommend  to help cavers safely explore the more difficult sections of the cave.

While you can hike the cave year-round, hiking Ape Cave in the winter is truly amazing! The visitor center is closed during the winter months, so lantern rentals are not available, and the upper parking area is often closed because of snow making the road impassable. In this case, I recommend snowshoes for the mile-long hike to the entrance. The cave can be very wet during this time of year, so waterproof shoes are the best.

You can hike the cave during the summer and fight the crowds in this popular cave, but there is nothing quite like being nearly alone in such a remarkable geological formation.

Driving Directions:

From Cougar, drive east on Forest Road 90 just 1 mile beyond the Swift Dam, and turn left (north) onto FR 83. Drive 2 miles on FR 83 and turn left onto FR 8303. Continue for 1 mile on FR 8303 to the trailhead on the right.

For more information about this hiking area please check out mountsthelens.com/ape-caves.

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Ape Cave Map


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