Mystery Photo 40 Revealed: The Glow Plug

It glows so bright, it's hard to fathom that it's natural. But indeed it is, in the form of molten lava. USGS photo.

An object so brightly hued can't be natural, can it? It can, if you know where in the National Park System to look.

And in this case you'd have to travel to Hawaii Volcanoes National Park to see this glow plug.

The glow in question is molten lava. But it's only visible thanks to a "skylight" cut into the top of a lava tube at the national park.

According to the USGS, which took the photographs, the "tube trace, which heads southeast, is marked by the line of fume sources in the upper right portion of the image. The surface flows, out of view in this image, were 1.1 km (0.7 miles) north of the uppermost street in Royal Gardens."