EARTH’S insides may move at a creep, but diamonds ride the fast track. Diamond-infused magma may zoom upwards from deep within the planet at a blistering 60 kilometres per hour.

Rising magma in Earth’s mantle is thought to ascend at just a few centimetres per year. It was known that kimberlite, which often contains diamonds, can rise more quickly near the surface, but its speed at great depths was unclear.

Now Masayuki Nishi and colleagues at Kyushu University in Fukuoka, Japan, have used the mineral garnet as a speedometer. Garnet inclusions that form inside diamond are stable at depths …