Seismic echoes reveal a mysterious ‘donut’ inside Earth’s core

About 2,890 kilometers beneath our feet lies a gigantic ball of liquid metal: our planet’s core. Scientists like me use the seismic waves created by earthquakes as a kind of ultrasound to “see” the shape and structure of the core.

Using a new way of studying these waves, my colleague Xiaolong Ma and I have made a surprising discovery: there is a large donut-shaped region of the core around the Equator, a few hundred kilometres thick, where seismic waves travel about 2% slower than in the rest of the core.