APE CAVES - Mt. St. Helens Lava Tube
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Mount St. Helens Ape Cave Lava Tube is a popular attraction in the Mount St.
Helens National Monument and the longest lava tube in the continental United
States at
over two miles in length.  The Ape Caves are located on the south
side of Mount St. Helens and accessed through Woodland - go up highway 503
past Cougar.  Driving time from I-5 and highway 504 where all the Mount St.
Helens Visitor Centers are to the Ape Cave is just over an hour.   The Ape Caves
are open year-round though the parking lot gets snowed in during the winter.   

Hiking the Ape Caves:   The lower Ape Cave is approximately is .75 miles long
and can be hiked down and back in an hour.  It is most famous for
“Meatball” - a
block of cooled lava which fell from the lava tube ceiling while lava was still flowing
through the cave.   Floating on the surface of the lava flow it was carried
downstream until it became wedged in a narrow spot above the present cave

Another feature is the “Railroad tracks” – a shoulder or levee that formed along
the side of the lava flow. As the fluid lava drained out of the tube, the levee
remained.  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.

The upper Ape Cave is 1½-mile long and takes about 2½ hours to complete,
returning on a surface trail. This section is more adventurous as cavers must climb
over approximately 27 boulder piles and scale an 8-foot high lava fall.  The
boulder piles formed after the eruption subsided and the fluid lava drained from
the tube. As the lava tube cooled, it began to shrink and crack. These cracks
weakened the ceiling and walls causing parts of them to collapse – forming
entrances to Ape Cave.   Note there is a skylight hole in the tube near the upper
exit however the trail continues on through the tube to a permanently attached
metal ladder.  Exiting the cave through the skylight is off limits.   During the
summer, a national monument interpretive naturalist leads tours through the lower
part of the cave.  Recommended equipment for exploring the Ape Caves is sturdy
shoes or boots, warm clothing, and three sources of light.

Ape Cave Hiker USFS Regulations:

  • No food, beverages, alcohol or
  • No smoking, No flares, fireworks,
    firearms or any kind of open flame
  • No rock collecting or damaging cave
    features ($200 fine).
  • No pets !
  • Do not touch the walls - Cave “slime”
    lives on the cave walls and is an
    important food source for cave life.

How the Ape Caves were formed:  About 2,000 years ago lava poured down
the southern flank of Mount St. Helens in streams.  As the lava flowed the outer
edges of the lava stream cooled forming a hardened crust which insulated the
molten lava beneath.  This allowed the lava to remain hot and fluid encased in this
“lava tube” and continued flowing months during the eruption.  The end result was
the creation of this spectacular 13,042 long lava tube.  This formation is especially
unusual at Mount St. Helens as this type of volcano usually erupts lava of a much
thicker consistency which tends to block flow and build up pressure resulting in
explosive eruptions like the blast of 1980.  

Watch out for the Wild Apes !  Mount St. Helens has long been famous as an
area of frequent Bigfoot, Sasquatch or “Hairy Ape” sightings.    

    Nearby “Ape Canyon” was the sight of the famous reported
    skirmish between Miners and a family of Bigfoot back in 1924.  
    The incident has become a legend in the Northwest – here is
    the bigfoot story from one of the miners - "I FOUGHT THE
    APEMEN OF MOUNT ST. HELENS, WA".  However, I wouldn’t
    worry too much about seeing bigfoot in the Ape Caves –
    common lore attributes the name to a scout troop who explored
    the caves back in the early 50’s.  Apparently the troop’s
    sponsor was the St. Helens Apes – a group of foresters.  
Foresters and loggers in those days were sometimes referred to as “Brush
Apes”.   Perhaps this is the origin of the name though those that have claimed to
have seen bigfoot in the area believe the caves would have been a perfect habitat
for the reclusive creatures.

Ape Cave Vicinity Map:
(map drawings courtesy USFS.)
Ape Caves -
Lower Ape Cave Trail Map
Upper Ape Cave Trail Map
Ape Cave Entrance
Mount St. Helens Ape Cave
Above - USFS photo
showing Ape Cave.  Below
artistic photo of Ape Cave
Skylight  ©
Unique geologic formation in
lower Ape Cave - referred to
as "MeatBall".  
Dated USFS
photo - who has a better one ?
Ape Cave Driving Map
Ape Headquarters
Typically Opens in June
the season.

Fee: During the summer, a
Northwest Forest Parking
Pass is required - $5/day,
$30/season.  When snow
comes, a sno-park pass is
required and cavers must
walk/snowshoe about one
mile from the Trail of Two
Forests parking area.  
Passes can be purchased
at the store in Cougar and
also at Johnston Ridge
Observatory.  The annual
pass also admits one to
Johnston Ridge
13,042 Ft. LONG !