The Boulder Cave
National Recreation Trail
10061
Highway 12
Naches, WA
August 6th, 1998
Boulder 
Cave is
home to the Pacific Western big-eared bat and other bat species. 
Approximately 50 big-eared bats use the cave as a hibernaculum to
survive the winter. The cave is closed to the public November 1
thru April 1 to reduce disturbance to the bats. During the 1920's
and 30's the Boulder Cave bat population numbered around a
thousand. Since this time public use has increased, while
the bat population has declined. Bats are an important component
of the ecosystem, preying primarily on insects. The big-eared
bats feed mainly on moths. Some of these moths defoliate the
forest. Boulder Cave was developed in rocks of the Yakima Basalt
Formation. A series of lava flows and interflow sediments that
were deposited in the area about 10 to 15 million years ago. The
actual cave is estimated 
to be less then 25,000 years old. The
cave was created by Devil Creek as it downcut into the Yakima
Basalt. As the stream eroded through the first flow, it
encountered a soft interflow layer of soil, gravel and loose
rock. The stream undercut the overlying Basalt causing it to
collapse into the canyon. The Boulder Cave National Recreation
Trail is approximately 1.5 miles round trip and will take about
an hour. There's a 200 foot elevation gain. A flashlight and a
good pair of walking shoes are recommended. There is no drinking
water available on the trail. Boulder Cave, the largest of its
kind in North America was discovered by a party of prospectors on
August 2, 1901.
Cave is
home to the Pacific Western big-eared bat and other bat species.
Approximately 50 big-eared bats use the cave as a hibernaculum to
survive the winter. The cave is closed to the public November 1
thru April 1 to reduce disturbance to the bats. During the 1920's
and 30's the Boulder Cave bat population numbered around a
thousand. Since this time public use has increased, while
the bat population has declined. Bats are an important component
of the ecosystem, preying primarily on insects. The big-eared
bats feed mainly on moths. Some of these moths defoliate the
forest. Boulder Cave was developed in rocks of the Yakima Basalt
Formation. A series of lava flows and interflow sediments that
were deposited in the area about 10 to 15 million years ago. The
actual cave is estimated to be less then 25,000 years old. The
cave was created by Devil Creek as it downcut into the Yakima
Basalt. As the stream eroded through the first flow, it
encountered a soft interflow layer of soil, gravel and loose
rock. The stream undercut the overlying Basalt causing it to
collapse into the canyon. The Boulder Cave National Recreation
Trail is approximately 1.5 miles round trip and will take about
an hour. There's a 200 foot elevation gain. A flashlight and a
good pair of walking shoes are recommended. There is no drinking
water available on the trail. Boulder Cave, the largest of its
kind in North America was discovered by a party of prospectors on
August 2, 1901.