Relative age dating and absolute age dating
Principles of Stratigraphy Stratigraphy is the study of strata (sedimentary layers) in the Earth's crust.
Geologist in the 1800s worked out 7 basic principles of stratigraphy that allowed them, and now us, to work out the relative ages of rocks.
Tradition paleontological and biostratigraphic correlation methods are still perhaps the most common relative dating methods used by geologists.
More modern correlation technologies include use of marine stable isotope records, paleomagnetic dating, tephrachronology, geomorphological methods, sedimentation characteristics, and other geochemical and radiometric methods.
A geologic map or report typically is only a summary of investigations that frequently involve the collecting and processing of hundreds of rock samples, followed by the evaluation and interpretation of data from a variety of analytical techniques.
A relative age is the age of a fossil organism, rock, or geologic feature or event defined relative to other organisms, rocks, or features or events rather than in terms of years.
New dating methods are invented all the time, however, most have practical limitations.
He published the results of his work and established a basic set of principles for interpreting sedimentary strata.
From the beginning of this course, we have stated that the Earth is about 4.6 billion years old.
How do we know this and how do we know the ages of other events in Earth history?
Prior to the late 17th century, geologic time was thought to be the same as historical time.
Archbishop James Ussher of Armagh, Ireland, 1654, added up generations from the Old Testament and determined that Earth formed on October 23, 4004 BCE.