The Boulder Cave National Recreation Trail
10061 Highway 12

Naches, WA

August 6th, 1998


Boulder Map nameCave is home to the Pacific Western big-eared bat and other bat species. image-01 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 image-03 to be less then 25,000 years old. Theimage-02 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.

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