Imagine you had a crystal ball that revealed when a volcano would next erupt. For the hundreds of millions of people around the world who live near active volcanoes, it would be an extremely useful device. As it turns out, certain crystals really can help us forecast volcanic eruptions. These crystals are produced in molten rock as it travels from deep inside Earth to the surface. With increasingly sophisticated scientific methods, we can extract a secret history of volcanoes from these crystals – the why, where and when of past eruptions. These historical records can help us interpret if signs…