Because nothing says room quite like a 1,000 year-old quarter-mile underground tube made from lava. This is just one part of a short, but sweet tour. Just as a frame of reference, the tip of that rocky outcropping at the bottom is nearly 5 feet tall.
Polymathically 
These are amazing. I still don’t fully understand why the lava doesn’t harden and fill the tubes, and just erode away from inside like that.
I know, they’re freaking awesome. Next time I go to Hawaii, I’m definitely checking out more of them. Apparently the Hana Lava Tube is much bigger, but guest access is limited to only that 1/4 mile section due to safety issues. It was also Maui’s nuclear fallout shelter during the Cold War!
As far as how they’re formed, it has a lot to do with insulation and cooling. Basaltic lava is like a river; it carves through land and flows toward the lowest point. But once it hits the open air here on the surface, it cools off pretty quickly. It’s kinda like seeing a pond freeze in the winter. However, only top parts of an active flow solidify; the crusted parts act like a shield for the lava underneath it. With nothing to cool it off, the underground flow will continue digging deeper and deeper. The heat and gas coming from the lava also make the ceiling and walls melt and reform. This weird balancing act between hot and cold are what create the weird formations that are unique to lava tubes. There’s one part of the Hana Lava Tube that, due to the heat, has a ceiling composed of what look like thousands of Hershey’s Kisses! Once the eruption stops, the lava drains out, leaving the tube it formed behind.
What an usual and interesting choice!
janet
Really nice idea. And good picture!
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