The Law of superposition is about the placement of one rock on top of another in the geology definition of the law, to tell the youngest layer (top layer) that in the sheet is in yellow. The rock layers position can determine the relative and absolute age of the deposition of the rock material, so much for the inorganic as well for the organic material found in the layer. The wavy erosional line are the unconformity break in time in an continuous rock structure record caused by a period of erosion or a pause in the sediment accumulation.