A huge well of molten carbon that would spell disaster for the planet if released has been found under the US. Scientists using the world's largest array of seismic sensors have mapped a deep-Earth area, covering 700,000 sq miles (1.8 million sq km). This is around the size of Mexico, and researchers say it has the potential to cause untold environmental damage. The discovery could change our understanding of how much carbon the Earth contains, suggesting it is much more than we previously believed. It would be impossible to drill far enough down to physically 'see' the Earth's mantle,...