Unless a major geological phenomenon has distorted the layers in sedimentary rock, layers that formed first are found beneath layers that formed later. By comparing rock layers exposed at different places across a landscape, the order in which those rock layers formed can be determined. This process, which places rocks in chronological order, is called relative dating. In the image above, different rock layers are shown in different colors. Nothing has happened to distort the layers. Compare the age of the pink rock layer to that of the dark red rock layer.