An extinct Hawaiian volcano called Pūhāhonu is the largest in the world, with a volume twice that of the next leading contender. What’s more, the lava that once erupted from Pūhāhonu is the hottest recorded in the past 66 million years.

“Pūhāhonu is the most massive volcano on Earth,” says Michael Garcia at the University of Hawai’i at Mānoa in Honolulu.

At the surface, Pūhāhonu doesn’t look like much: just a pair of barren, rocky outcrops hundreds of kilometres north-west of …