One of the top attractions of the Big Island's renowned Hawaii Volcanoes National Park is a "journey to the center of the earth'' through the Thurston Lava Tube. This short hike takes visitors right inside a recently active volcano - Kilauea - which was responsible for a 1959 eruption that produced spectacular lava fountains - among the hottest and highest in Hawaiian history.
Lava tube caves are formed when fluid lava passes through the earth's crust to the surface. The longest and most vertically extensive lava tubes in the world are found on the Big Island of Hawaii. As lava flows down the side of a volcano, the upper layer cools and solidifies. The molten lava below is insulated by the hardened lava and continues to flow in conduits beneath the surface, sometimes for great distances underground, with very little cooling.
A few Hawaiian tubes have carried lava 50 miles or more from their source. Once drained of the molten rock, the empty tubes are much like limestone caves. They often have stalactites and stalagmites. Their walls, however, may be smoothed or rutted by the lava that created them.
The entrance to the Thurston Lava Tube, also called "Nahuku,'' can be found at the east side of the parking lot, away from Kilauea Crater near the park's Visitor Center. There is an interpretive sign posted by the parking lot fence, and it directs hikers up an easy climb leading off to the right where the lava tube walkway begins. The entry point is surrounded by lush rain forest vegetation, giving little indication of the mighty forces that formed this terrain.
The path descends gradually, and then more steeply, covering about a third of a mile on the way to the tube's orifice. A bridge must be crossed to the mouth of the tube, and it leads down to a nearly flat lava floor. The interior of the Thurston Lava Tube has been lit with electric bulbs to permit viewing, although it is a good idea to bring along a flashlight to explore features hidden by the natural darkness.
It is evident how the flowing magma smoothed the tube's otherwise rugged walls. There are tree roots hanging down from the ceiling and water drips through cracks in the rock above. When the tube was first discovered in 1913 by Lorrin Thurston, a local newspaper publisher, the roof was covered with lava stalactites, too. However, these soon disappeared, carried away by souvenir collectors.
Visitors walking through the tube need to be mindful of the low ceiling in spots, but there are no real dangers associated with the tube. The lava stopped flowing here hundreds of years ago. It currently travels from Pu'u O'o to the ocean via a labyrinth of separate lava tubes much like this one.
At the far end of Thurston Lava Tube, a set of stairs leads back to the surface. From here, the rest of the volcanic crater can be explored along the Kilauea Iki Trail to the rim, or visitors may loop back to the parking lot along the rain forest path.
The Kilauea Visitor Center is located at Crater Rim Drive, Hawaii Volcanoes National Park, Hawaii 96785. Rangers are on duty here to provide assistance for hikers, including trail information, maps, and permits. The center is open from 7:45am to 5pm daily. The entry fee is $10 per vehicle.