I was rather taken by the vivid graphic on this sign alongside the Sulphur Banks Trail in Hawaii Volcanoes National Park. But it illustrates an incident from 1996 when a 10-year-old boy wandered off the trail and his foot went through the crust into a steaming vent leaving him with serious burns. That small, dark hole in the upper left of the photo is one such vent and it was busily steaming away while I read the gory details.

For more information about Hawaii Volcanoes National Park, go to nps.gov/havo/.