Scientists are keeping a wary eye on our planet's 20 or so supervolcanoes—like the one at Yellowstone National Park—wondering when they will erupt with devastating effects. Now Swiss researchers say that supervolcanoes don't require an external trigger such as an earthquake to cause an eruption; molten lava alone will do the trick, the BBC reports. "A supervolcano can erupt due to its enormous size alone," says Wim Malfait, who led the study. "Once you get enough melt, you can start an eruption just like that."
His team simulated a volcano's intense pressure by loading synthetic magma into a diamond capsule and monitoring it with high-energy X-rays. As the magma went from solid to liquid, it created pressure strong enough to break through the Earth's crust and cause an eruption. But don't worry yet, Malfait says: Yellowstone isn't close to its first eruption in 600,000 years, because its "partial melt" is only at 10%-30%, and requires 50% to erupt. Still, "this is something that, as a species, we will eventually have to deal with. It will happen in future."