The discovery of an unexpectedly hot rock beneath Earth’s surface is challenging scientists’ understanding of how heat is distributed deep inside the planet, with potential implications for how they understand earthquakes, volcanic activity and the movement of carbon through Earth.

An international research team focused on a rock from northern Papua New Guinea, where the Australian and Pacific tectonic plates move toward each other, causing rocks to be carried deep underground through a process known as subduction.

The researchers found that the rock experienced temperatures of about 800°C (1,472°F) at a depth of 45 kilometers (28 miles) below the surface and became about 100°C colder after reaching depths of more than 90 kilometers (56 miles).