Geology group treated to rare pool explosion

"Yellowstone National Park geologist Hank Heasler was lecturing a group of colleagues in Biscuit Basin on the rarity of hydrothermal explosions last week when – Boom!

"A hot pool behind him exploded, spewing mud, rocks and hot water 50 feet in the air. Geologists know of only a handful of such unpredictable explosions in Yellowstone’s recorded history."

The natural history of hydrothermal explosions in Yellowstone.