Thurston Lava Tube

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600-foot, well-lit lava tube formed several hundred years ago during an eruption when low-viscosity lava flowed through this area. The upper layer of the flow cooled first, forming a hard crust, while the molten lava beneath continued to flow in tubular conduits beneath the surface. Because of the insulation of the upper crust, the liquid magma stayed heated enough to travel quite a distance before solidifying as well.