Arthur's Seat and the Salisbury Crags adjoining it helped form the ideas of modern geology as it is currently understood. It was in these areas that James Hutton observed that the deposition of the sedimentary and formation of the igneous rocks must have occurred at different ages and in different ways than the thinking of that time said they did. It is possible to see a particular area known as Hutton's Section in the Salisbury Crags where the magma forced its way through the sedimentary rocks above it to form the dolerite sills that can be seen in the Section.