Relative dating of sedimentary rocks
* Stratigraphy Stratigraphy is the study of rock layers (strata) and their relationship with other other.Stratigraphy provides simple principles used to interpret geologic events as discussed below.to compare the ages of two or more artifacts, rocks or even sites.Difference between relative dating and absolute dating of rocks .Thus if we observed rock layers that are folded or inclined, they must, with exceptions, have been moved into that position by crustal disturbances sometime after their deposition.Principle of superposition The principle states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.Therefore, deeper layers must be older than layers closer to the surface. You can see an example in Figure below and at the link below.[Link about law of superposition here.] Rock layers extend laterally, or out to the sides.They may cover very broad areas, especially if they formed at the bottom of ancient seas.
What is the difference between relative and absolute dating of rocks .Along the way, we'll learn how stratigraphic succession and radioactive decay contribute to the work of paleontologists.Consider the following scenario: Paul the Paleontologist is a very famous scientist who has studied dinosaur bones all over the world.Erosion may have worn away some of the rock, but layers on either side of eroded areas will still “match up.” Look at the Grand Canyon in Figure below. You can clearly see the same rock layers on opposite sides of the canyon.
The matching rock layers were deposited at the same time, so they are the same age.The relative ages of rocks are important for understanding Earth’s history.New rock layers are always deposited on top of existing rock layers.Lecture 10 Stratigraphy and Geologic Time * Stratigraphy * Basic principles of relative age dating * Unconformities: Markers of missing time * Correlation of rock units * Absolute dating * Geologic Time How old is the Earth? Interpreting Earth history is a prime goal of geology.