Nahuku, the Thurston Lava Tube, gives the visitor an opportunity for a close-at-hand inspection of the inner plumbing of a volcano. It also makes for an interesting and unique way to escape the noonday heat or afternoon shower briefly. Lava tubes form when the outer crust of a flowing river of lava begins to cool and crust over, but the lava continues to flow beneath it; when the flow has completely drained away, the lava tube is left behind.
Thurston lava tube is a remarkably large, well-preserved and accessible example of a lava tube-type cave. An easy, 0.3 mile trail (about a 15 minute hike) winds through lush fern forest alive with singing bird and buzzing insects, down into a collapse crater entering the lava tube and slipping about 300 feet through the well-lighted, floored cave, popping up through a skylight in the tube and returning to the parking lot. A very easy walk and certainly a “must see” for any visitor to the park.
When Lorrin Thurston, founder of the Honolulu Advertiser, found the cave in 1913, the roof reportedly was covered with stalactites—it is said that rapacious tourists removed every one in the intervening years.