Ape Cave Lava Tube

Duplicate Location

Ape Cave lava tube, which formed in one of these basalt flows ... (Cave Basalt flows about 2,000 years ago) ... is the longest lava tube (12,810 feet or 3.9 kilometers) in the conterminous United States (similar tubes are found in Oregon, California, and Idaho) and one of the longest in the world. The cave was constructed by a pahoehoe flow that crusted over, soon after, the molten lava on the inside drained away, leaving the outer crust in place. Lava stalactites and stalagmites and flow marks can be seen on the walls and floor of the cave. Lava stalactites, conical or cylindrical deposits of lava that hang from the ceiling of a tube, are formed by dripping, stalagmites are similar in shape and are formed on the floor of the tube by the accumulation of drips from the ceiling. Some time later, a sandy lahar flowed into the cave, possibly in A.D. 1480 or 1482 because the deposit contains white pumice granules that resemble W tephra. During the summer, a national monument interpretive naturalist leads tours through the lower part of the cave. Be sure to read the brochure (available at the cave entrance) to find out more about the cave and the equipment you will need if you plan to explore on your own. (Sturdy shoes or boots, warm clothing, and three sources of light are recommended.