Isotope analysis of gas from geothermal springs in Zambia could show that a new continental rift is forming, scientists say. Unexpectedly high helium isotope ratios indicate that a weakness in Earth's crust has broken through to reach the mantle beneath. This rift could eventually become a new tectonic plate boundary. In the meantime, opportunities for geothermal energy could boost local economies.

"The hot springs along the Kafue rift of Zambia have helium isotope signatures which indicate that the springs have a direct connection with Earth's mantle, which lies between 40 and 160km below Earth's surface," said Prof Mike Daly of the University of Oxford, an author of the article in Frontiers in Earth Science.

"This fluid connection is evidence that the fault boundary of the Kafue Rift is active and therefore the Southwest African Rift Zone is too—and may be an early indication of the break-up of sub-Saharan Africa."