Yellowstone is the world’s largest active volcanic systems – whose eruption is hundreds of times more powerful than Vesuvius’ blast and ash could blanket half the US – and yet scientists could not agree on what drives its underground magma system.

But a new finding detailed by Chinese researchers could settle the dispute.

They declared that Yellowstone’s magma channels were not blasted open by magma forcing its way upward. Instead, tectonic forces tore the lithosphere apart first and only then...