The truth about a terrifying lava skylight where only the trained should lurk

This digitized slide was taken during fieldwork, in 1996,  within Hawaii Volcanoes National park, by the USGS Hawaiian Volcanoes Observatory. Such skylights are generally off-limits to park visitors because they are very dangerous to approach due to the possibility of further roof collapses and the extremely hot air that blows out of the skylight.

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This particular skylight, Dr. Laszlo Kestay explains, was located on the coastal flats below Pulama Pali, an excellent location for conducting scientific observations. The photogenic toes of pahoehoe lava frozen around the sides of the skylight are from a lava flow that moved across the skylight and sent lava cascading back into the tube.

During much of the 35 years of the Kilauea eruption, lava has quietly flowed from the Puu Oo vent to the ocean through insulating lava tubes. These lava tubes form as small (ankle-to-knee deep) pahoehoe. These flows are "inflated" by the injection of more lava into their still molten interior, resulting in lava flows a few meters (yards) thick. The movement of the lava becomes focused into narrow pathways as less favorable routes freeze. This "river" of lava flowing under an insulating crust is a lava tube. In some locations, this roof collapses, providing a "skylight" onto the stream of fluid lava.

“Having an active surface flow cross over an active skylight is a bit of a rare coincidence, so this was definitely worth taking a photo - even back in the days of film cameras where you had quite a limited number of shots you could take,” said Dr. Kestay.