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On Sunday morning we hopped in my dad's Land Cruiser and drove down to Mount St. Helens National Monument to explore Ape Cave.
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It was discovered in 1951 by Lawrence Johnson, who nearly drove his tractor into the bottom entrance, above.
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His friend Harry Reese had three sons, members of a local outdoor exploration club called the Mount St. Helens Apes; they called the lava tube Ape Cave, and the name stuck.
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After a short walk to the top of the tube, we made our way underground. Emily and I have been to Mammoth Cave in Kentucky, which is gigantic, but feels a little less remote because all the tours are guided. Here you're on your own, save for the other explorers you pass along the way.
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At over two miles in length, this is the longest known lava tube in the country. It's pitch black and a steady 42º inside.
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If you go, be sure to bring a headlamp and a good flashlight. It's not a strenuous walk, but some scrambling is required as you pick your way over the rocks, so it's good to wear some stiff-soled shoes or hiking boots.
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When we were done we stopped in at Cougar, WA for some provisions, and hit the road. It was a cool trip.