Relative dating wikipedia
The concept is considered by uniformitarian geologists to be a major breakthrough in scientific reasoning by establishing a rational basis for relative time measurements.However, unlike tree-ring dating -- in which each ring is a measure of 1 year's growth -- no precise rate of deposition can be determined for most of the rock layers.The atoms of some chemical elements have different forms, called isotopes.These break down over time in a process scientists call radioactive decay.All radiometric dating methods measure isotopes in some way.Most directly measure the amount of isotopes in rocks, using a mass spectrometer.Because of the fairly fast decay rate of carbon-14, it can only be used on material up to about 60,000 years old.Geologists use radiocarbon to date such materials as wood and pollen trapped in sediment, which indicates the date of the sediment itself.
Some types of relative dating techniques include climate chronology, dendrochronology, ice core sampling, stratigraphy, and seriation.
Geologists often need to know the age of material that they find.
They use absolute dating methods, sometimes called numerical dating, to give rocks an actual date, or date range, in number of years.
Relative dating is a dating method that used to determine determine the relative ages of geologic strata, artifacts, historical events, etc.
This technique does not give specific ages to items.Between the years of 17, James Hutton and William Smith advanced the concept of relative dating.