Subsequent activity has been focused within the area of the National Park, and another huge eruption 631,000 years ago formed the Yellowstone caldera as we now see it. The three caldera-forming eruptions, respectively, were about 6,000, 700, and 2,500 times larger than the May 18, 1980 eruption of Mt. St.

Approximately 630,000 years ago, the Yellowstone region experienced a cataclysmic "supervolcanic" eruption known as the Lava Creek Eruption. This event was roughly 1,000 times more powerful than the 1980 eruption of Mount St. Helens. It expelled an estimated 240 cubic miles of rock, dust, and volcanic ash into the atmosphere, covering much of western North America. The sheer volume of material ejected caused the ground above the magma chamber to collapse, creating a massive crater known as the Yellowstone Caldera, which measures approximately 30 by 45 miles. This caldera forms the central basin of what is now Yellowstone National Park. The heat remaining from this and subsequent smaller volcanic events continues to power the park’s iconic geothermal features, such as Old Faithful and the Grand Prismatic Spring. In 2026, geologists continue to monitor this "hotspot" closely, as the 630,000-year-old collapse remains the primary geological architect of the park's unique and volatile landscape.