A dormant supervolcano close to home is in Yellowstone National Park. According to Joel Achenbach, a reporter on science and politics for The Washington Post, three super-eruptions have occurred there, with one just 640,000 years ago (a blink of an eye in geologic terms). Even more powerful was a super-eruption 2.1 million years ago that “[left] a hole in the ground the size of Rhode Island” (Achenbach 1). The caldera, or crater, of the Yellowstone supervolcano is about 45 miles across, and over time, has been eroded and covered by glaciers and forests; part of the caldera’s rim is invisible, hidden beneath the surface of Lake Butte (Achenbach 2).

It was thought that the volcano was extinct, but activity is making scientists re-think that view. A huge magma chamber lies deep under the volcano’s caldera. When shifted by earthquakes and pressed by hot rock, the land above it rises and falls. An earthquake swarm in the mid-1980s made Yellowstone drop, so that it was about eight inches lower ten years later (Achenbach 2). More recently, “portions of the caldera have surged upward at a rate of nearly three inches a year, much faster than any uplift since close observations began in the 1970’s” (Achenbach 3). Such activity indicates a live volcano.

The last three super-eruptions have been in Yellowstone itself. The most recent, 640,000 years ago, was a thousand times the size of the Mount St. Helens eruption in 1980, which killed 57 people in Washington. . . . And this wasn’t even Yellowstone’s most violent moment. An eruption 2.1 million years ago was more than twice as strong, leaving a hole in the ground the size of Rhode Island.. . . For all their violence, the supervolcanoes have left little behind beyond a faintly perceptible sense of absence. The Yellowstone caldera has been eroded, filled in with lava flows and ash from smaller eruptions (the most recent was 70,000 years ago) and smoothed by glaciers. Peaceful forests cover any lingering scars. . . . We’re standing atop Lake Butte,. . . But I can’t follow the caldera rim visually because much of it is beneath the lake and because of the sheer scale of the thing—roughly 45 miles across.. . . About five to seven miles deep is the top of the magma chamber, a reservoir of partially melted rock roughly 30 miles wide . . . After the 1985 earthquake swarm, Yellowstone fell eight inches over the course of a decade or so. Then it rose again, faster this time. Since 2004, portions of the caldera have surged upward at a rate of nearly three inches a year, much faster than any uplift since close observations began in the 1970s.