Between these two layers is a thinner layer of Carboniferous sandstone , which was baked hard when the Whin Sill was molten 295 million years ago .
The lower section is made up of Carboniferous Limestone , a softer rock which is more easily worn away by the waterfall .
Between these two layers is a thinner layer of rock sandstone , which was baked hard when the Whin Sill was molten 295 million years ago .
The lower section is made up of Carboniferous Limestone , a softer rock which is more easily worn away by the waterfall .