Rules of relative dating
An example of this is given in Figure 8.7, which shows three different sedimentary layers.
Playfair later commented that, "the mind seemed to grow giddy by looking so far into the abyss of time." Mc Phee (1998) points out that Hutton removed humans from a specious place in time just as Copernicus had removed humans from a specious position in the universe (p. Hutton gives us three more laws to consider when seeking relative dates for rock layers, one of which, the law of inclusions was described earlier.states any feature that cuts across a rock or sediment must be younger than the rock or sediment through which it cuts.The realization that sediments turn into rock was counter to the view that all rocks on Earth formed in a single creation event.Once Steno recognized that the fossils he was contemplating (sharks teeth and sea shells) were formed in the sediments of oceans he was able to work out the basic rules of stratigraphy.Not only did the rock layers indicate changing environments they also revealed that different life forms have existed in different times.The simplest and most intuitive way of dating geological features is to look at the relationships between them.
An example of an unconformity is shown in Figure 8.8.