http://www.skamania.org/spelunking.htmlCenturies-old eruptions of pumice and lava from Mount St. Helens created numerous geologic attractions on its south flank. Lava tubes and caves, formed in the cooling lava, range from thousands of feet in length to small bubble like chambers. Most are located on the Mount St. Helens National Volcanic Monument or the Mt. Adams Ranger District.
Ape Cave is the longest known lava tube in the continental U.S. (12,810 feet). Be prepared by wearing warm clothing, heavy boots, and head protection. When you enter the caves, be sure to take at least three sources of light. In the summer, lamps can be rented at the nearby Ape Cave Headquarters, where interpretive walks are also available.
Within 1 mile of Ape Cave is the Trail of Two Forests. Explore a 1/4 mile, barrier-free boardwalk interpretive trail through a lava tree cast area and plan for a relaxing break at the picnic area.
Ice Caves
This ice cave was
detected almost 140 years ago and served as an ice supply for Hood River and The Dalles in pioneer year. The entrance is in the Gifford-Pinchot National Forest just east of Trout Lake, WA.
Total length of the cavern, accessible from a ladder at the main entrance, is about 650 feet. The cave is usually snowed in until at least mid-June of each year, and refreezing begins in October or November.
Visitors should wear warm clothing, boots, head protection and carry a minimum of two sources of light.
http://www.travel-in-wa.com/TRAVEL/facts.htmlApe Cave (Mount St. Helens ) - formed from a basalt flow over 2,000 years ago; at 12,810' this is the longest lava tube in the 48 contiguous states, and one of the longest of its kind in the world; explore it by hiking up the Ape Cave Trail (see Mt. St. Helens in National Parks under our "Outdoor Fun" section).