Ape Cave lava tube, is the longest intact
stretch of
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.
Named by members of an outdoor group called the Mt. St. Helens Apes,
this cave has two different exploration routes: the upper cave
and the lower cave. The lower cave is a relatively easy 0.75
mile hike that takes 1 hour round trip. The challenging upper cave
is 1.5 miles long, requires climbing over large piles of rocks and
takes 2.5 to 3 hours. The cave dead-ends at a tiny
crawl, that is too small to fit through. All the bats that
used to inhabit this cave are gone now, as the cave has become a
tourist attraction. Also gone are many species of molds and
fungi that used to attach themselves to the lava formations.
We've strolled numerous times through both the upper and lower
caves, and it's a fun, if touristy, thing to do. Portions of
the cave are even suitable for small children.
The cave was constructed by a
d three sources
of light are recommended.