Relative dating exercise 1
Imagine that you're a geologist, studying the amazing rock formations of the Grand Canyon.Your goal is to study the smooth, parallel layers of rock to learn how the land built up over geologic time.
Once we assume that all rock layers were originally horizontal, we can make another assumption: that the oldest rock layers are furthest toward the bottom, and the youngest rock layers are closest to the top. The forest layer is younger than the mud layer, right? When scientists look at sedimentary rock strata, they essentially see a timeline stretching backwards through history.The Principle of Original Horizontality states that due to the influence of gravity all sediment is originally deposited horizontally.In other words, as sediment fills a depositional basins we would expect the upper most surface of the sediment to be parallel to the horizon. Using this principle we can than assume that sedimentary layers which have been deformed/folded must have been deformed after all affected layers have been deposited.Much like the principle of cross-cutting, the Principle of Inclusions relatively dates objects based on their placement within other earth materials.Once a rock is lithified no other material can be incorporated within its internal structure.