In central Africa is a deep lake that has a dangerous propensity to explode – but tapping it as a source of energy could help avert disaster. Lake Kivu is one of Africa’s strangest bodies of water. An unusual set of properties make it an intriguing subject for scientists, as well as a potential source of both peril and prosperity for the millions of people living nearby. Kivu doesn’t behave like most deep lakes. Typically, when water at the surface of a lake is cooled – by winter air temperatures or rivers carrying spring snowmelt, for example – that cold,...