Once upon a time, Yellowstone National Park was thought to be a death trap. Okay, maybe death trap is too strong. But what else would you call a super volcano that could wipe out two-thirds of the U.S.?
It would explode with a force a thousand times more powerful than the Mount St Helens eruption in 1980.
Spewing lava far into the sky, a cloud of plant-killing ash would fan out and dump a layer 10ft deep up to 1,000 miles away.
Two-thirds of the U.S. could become uninhabitable as toxic air sweeps through it, grounding thousands of flights and forcing millions to leave their homes.
Needless to say, it’s an event that is worth breaking a sweat over. But I have some bad news, and some good news. The bad news is that the magma reservoir underneath Yellowstone National Park is at least two and a half times larger that originally thought. The good news is that earthquakes, not volcanoes, will begin the End of Days.
Above the buried blob — in the topmost 5–10 kilometres of the crust — the rocks are cooler and more brittle, and fracture easily in earthquakes. Yellowstone is known for its swarms of earthquakes — in recent years, the Utah team has discovered tiny quakes that repeat as often as every few seconds2. Volcanic fluids build up in the crust and the small earthquakes probably act as relief valves to release the pressure. “It’s a living, breathing, shaking and baking place,” says Smith.
Yellowstone’s last mammoth volcanic eruption took place 640,000 years ago. Since then, some 50 to 60 smaller eruptions have occurred, with the most recent of these about 70,000 years ago. A much more likely risk than volcanoes, says Smith, is posed by earthquakes of magnitude 7 or greater like those that have struck the region in modern times. “They are the killer events which we’ve already had,” he says. For instance, the magnitude-7.3 Hebgen Lake earthquake that hit near Yellowstone in 1959 killed 28 people.
Somehow that doesn’t really seem like good news. I’m so sorry.