What is relative dating and radiometric dating
After students have decided how to establish the relative age of each rock unit, they should list them under the block, from most recent at the top of the list to oldest at the bottom.
The teacher should tell the students that there are two basic principles used by geologists to determine the sequence of ages of rocks.
A background in local and regional geology is especially important.
Students not only want to know how old a fossil is, but they want to know how that age was determined.
A nucleus with that number of protons is called lead (chemical symbol Pb). This particular form (isotope) of lead is called Pb-207.
U-235 is the parent isotope of Pb-207, which is the daughter isotope.
In general, with the exception of the single proton that constitutes the nucleus of the most abundant isotope of hydrogen, the number of neutrons must at least equal the number of protons in an atomic nucleus, because electrostatic repulsion prohibits denser packing of protons.The dating of land surfaces has long posed problems for geomorphologists.Relative methods (stratigraphic, geomorphic, topographic) are sound and convincing.They are: Principle of superposition: Younger sedimentary rocks are deposited on top of older sedimentary rocks.Principle of cross-cutting relations: Any geologic feature is younger than anything else that it cuts across.