They get uplifted, tilted, faulted, squashed and squeezed, and magma gets injected into them.
It’s all a bit of a mess—but a mess that can be put in chronological order using relative dating principles.
The Grand Canyon acts as a modern testament to stratigraphy and relative dating.
Both the principle of original horizontality and the law of superposition seem very intuitive and obvious, but they weren’t proposed until the 1600s, both by Danish anatomist, geologist, and priest Nicolaus Steno (1636–1686).
In a nice, simple world, we would have a complete and undisturbed record of sedimentary rocks to help us plot out Earth’s past. All kinds of things happen to rock layers after they form.
These ages have been derived from relative dating and absolute dating (radiometric dating) of rock layers and fossils.
(a) Relative Dating This technique uses principles of stratigraphy (rock strata) and the study of fossils (palaeontology) to determine the relative ages of rocks and sediments. Field geologists' rely on a number of simple techniques for dating rocks and constructing geological successions. The Law of Strata Identified by Fossils is a little bit more complex.(relative geologic timescale) (b) Absolute Dating Following the discovery of radioactivity in 1895, radiometric dating techniques were developed to determine the absolute ages, i.e. In the succession of strata, each layer represents the geographical conditions that occurred over that area at the time the layer was deposited.