Geologists have stumbled on what they call gigantic fortresses lying almost 1,800 miles below our feet in Earth’s mantle. New seismic evidence shows how these subterranean bulwarks are older and tougher than the cooler debris of dead ocean plates that surround them, turning a long‑running mystery into a concrete data story. Each fortress spans an area comparable to …
Read More »Gigantic ‘fortresses’ found deep underground in Earth’s mantle
