Ape Cave Lava Tube

Mt St Helens National Volcanic Monument

Cougar, Washington

Follow the signs off Forest Service Rd 90, north of Cougar

Ape Cave is a lava tube on the south side of Mt. St. Helens. At 2.5 miles long, it is the longest continuous lava tube in the United States. It is open for hiking, but be prepared for loose rock, rough surfaces and darkness.

Lava tubes are unusual in the Cascades because the Cascades volcanoes are mostly stratovolcanoes and thus do not usually erupt with fluid rock (pahoehoe). Ape Cave's length is especially noteworthy for that reason.


ape cave entrance

Entrance to Ape Cave (O04A0259)


inside ape cave

Inside Ape Cave (O04A0263)
The flashlight that I keep in the car is not adequate for caving purposes, so I stayed near the entrance when I headed down into Ape Cave lava tube.

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