Difference between relative dating and radiometric dating
The layers of rock at the base of the canyon were deposited first, and are thus older than the layers of rock exposed at the top (principle of superposition).
In the Grand Canyon, the layers of strata are nearly horizontal.
Accordingly, the oldest rocks in a sequence are at the bottom and the youngest rocks are at the top.A fossil can be studied to determine what kind of organism it represents, how the organism lived, and how it was preserved.However, by itself a fossil has little meaning unless it is placed within some context.This is the principle of original horizontality: layers of strata are deposited horizontally or nearly horizontally (Figure 2).Thus, any deformations of strata (Figures 2 and 3) must have occurred after the rock was deposited.
Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.