Togographic expression of an active lava tube. Although lava tube can be easily identified by the trail of steam coming out of the lava flow field, it is rare to find a clear topographic expression of a tube. Here on the left, we see the convex, elongated structure of the tube in the darker lava with steam coming out and covered by a fallen tree. The surface expression of the tube dives down and pinches into the lava flow field towards the right. We crossed the surface of the lava tube several times in our hike towards the ocean entry. The lava tube begins at the top of the slope, going downhill (in the south direction) and then makes what appears to be an abrupt turn towards the east to flow parallel to the coast before turning again towards the south and making the ocean entry. We did not investigate if the turns were sharp, right angles or meandering, but it appeared that the overall lava tube had a meandering character. At times, the smell of sulfur dioxide was obvious. Also, even while walking over the tube for a short time I could feel the heat coming up through my boots. It was like walking on a hot asphalt road in the desert. The roof of the lava tube is expected to be about 0.5-1 m thick, and easily support people walking over it. Occasionally, a skylight can form over places where the roof has caved in and allow a spectacular view into a river of fast moving lava. We did not find any, and did not hunt for them either. Geoff Cook explained later how he found one last time and there was an intense amount of sulfur-rich gas spewing out that it was choking to be near it.
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