The East African Rift Valley is home to ancient pieces of crust, which are around 2-3 billion years old. What’s also special is the volcanic activity in the area. Africa is splitting away from Asia, and this movement of the Earth’s crust produces a lot of heat. “That helps drive the helium from the crystals in which it’s forming out into a gas phase which we can search for,” explains Professor Jon Gluyas from the University of Durham.