At the heart of Yellowstone’s past, present, and future lies volcanism. Catastrophic volcanic eruptions occurred here
- About 2 million years ago,
- then 1.2 million years ago,
- and then again 600,000 years ago.
The latest eruption spewed out nearly 240 cubic miles of debris. What is now the park’s central portion then collapsed, forming a 28- by 47- mile caldera (or basin). The magmatic heat powering those eruptions still powers the park’s famous geysers, hot springs, fumaroles, and mud pots. The spectacular Grand Canyon of the Yellowstone River provides a glimpse of Earth’s interior: its waterfalls highlight the boundaries of lava flows and thermal areas. Rugged mountains flank the park’s volcanic plateau, rewarding both eye and spirit.