Before this, scientists would use seismic waves in order to get information on the earth’s composition. This was how they discovered that there was an interruption between three to six kilometers below the surface of the earth. They believed that this interruption was caused by a transition in rock type.
But they didn’t find any change in rock type. What they did discover was that granite continued to the core of the earth but that it went through a metamorphic change. This was just one of many puzzling discoveries that they managed to make. Photo Credit: Credits