Unlike relative time, absolute time assigns specific ages to events or formations and is typically recorded in years before present.
This process requires much more sophisticated chemical analysis and, although other processes have been developed, often utilizes the decay rates of radioactive isotopes to determine the age of a given material.
It concentrates mainly on the placement of the strata as well as its chronological sequence.
The principle of superposition is the core principle used in this method.
This means that a quartz sandstone deposited 500 million years ago will look very similar to a quartz sandstone deposited 50 years ago.
Making this processes even more difficult is the fact that due to plate tectonics some rock layers have been uplifted into mountains and eroded while others have subsided to form basins and be buried by younger sediments.
Stratigraphy: This oldest relative dating technique in the branch of geology, as the name suggests, focuses mainly on the strata.The most obvious feature of sedimentary rock is its layering.This feature is produced by changes in deposition over time.However, this is mainly applicable to an undisturbed arrangement of rocks.Most of the rock arrangements are disturbed by natural forces, such as wind and water, which result in unconformity in the sequence of rocks.It is composed of rocks and sediments deposited over millions of years. It is the evidence of Earth's history over such a long span of time.It is a perfect example of superposition (layers deposited one above the other) and lateral continuity (undisturbed and covering large distances).This process lead to a system of time containing eons, eras, periods, and epochs all determined by their position in the rock record.For example, rocks of the Phanerozoic eon are found on top of rocks from the Proterozoic eons therefore rocks of the Phanerozoic are younger than rocks of the Proterozoic.Strata is the layered arrangement or soil or rocks which lie parallel, one above the other.Each layer has a unique layer and consists of different sediments or material.The absolute age of these events need not inevitably be known.Grand Canyon is a gorge located in Northern Arizona, USA. While some of the layers are uplifted, most of the landform is left undisturbed by nature.Biostratigraphy: Layers get deposited above one another, over time, and fossils get trapped in these layers.