How do scientists use radioactive dating 15 year old dating rules
The layers of rock are known as "strata", and the study of their succession is known as "stratigraphy".Fundamental to stratigraphy are a set of simple principles, based on elementary geometry, empirical observation of the way these rocks are deposited today, and gravity.There are situations where it potentially fails -- for example, in cave deposits.In this situation, the cave contents are younger than both the bedrock below the cave and the suspended roof above.Despite this, the "principle of cross cutting relationships" can be used to determine the sequence of deposition, folds, and faults based on their intersections -- if folds and faults deform or cut across the sedimentary layers and surfaces, then they obviously came after deposition of the sediments.You can't deform a structure (e.g., bedding) that is not there yet!It can't float in mid-air, particularly if the material involved is sand, mud, or molten rock.The principle of superposition therefore has a clear implication for the age of a vertical succession of strata.
In such a situation, the "principle of superposition" is easily applied, and the strata towards the bottom are older, those towards the top are younger.
An early summary of them is found in Charles Lyell's .
In no way are they meant to imply there are no exceptions.
As an example of how they are used, radiometric dates from geologically simple, fossiliferous Cretaceous rocks in western North America are compared to the geological time scale.
To get to that point, there is also a historical discussion and description of non-radiometric dating methods.
Much of the Earth's geology consists of successional layers of different rock types, piled one on top of another.