Why you weigh less in Cornwall

The Cornubian Batholith sounds like it could have been the thirteenth labour of Hercules but is in fact a mass of granite formed around 300 million years ago from magma that pushed it’s way up through the earth’s crust. Rather than erupting as a volcano the magma collected, a bit like a blister, just under the surface, cooling and solidifying as it did so. Since then the surface layers have been worn away, revealing areas of underlying granite. The bulk of it is still under the surface, beneath layers of the surrounding rock. The full extent and shape of the …