A hidden danger lurks beneath Yellowstone
Catastrophic hydrothermal explosions rocked the park in the past and could again in the future
The area around West Thumb Geyser Basin and Yellowstone Lake (in the background) has seen many hydrothermal explosions, which occur when hot water beneath the surface suddenly flashes into steam.
Martin Ruegner/Getty Images
Mount Ontake in Japan rises 3,067 meters above sea level — a windswept giant standing head and shoulders above densely forested hills.