A series of explosions created a silica-filled water pool to the left of Tree Basin in Yellowstone National Park.

(NEXSTAR) — There have long been questions about when Yellowstone’s volcanic system could see an eruption, especially after a massive hydrothermal explosion was caught on camera last summer.

A surprise eruption that shot steam, water and dark-colored rock and dirt dozens of feet into the sky Tuesday sent people running for safety in Yellowstone National Park. The hydrothermal explosion ...