6 rules relative age dating
The units commonly used for geologic age are mega-annum (Ma) for millions of years, giga-annum (Ga) for billions of years, and kiloannum (ka) ka for thousands of years.
If so, you have already practiced interpreting details of earth's history from the evidence contained in rocks.Steno made careful geologic observations and illustrations.He published the results of his work and established a basic set of principles for interpreting sedimentary strata.A few centimeters a year, about the rate your fingernails grow, may not seem like much but, as millions of years of geologic time unfold, it adds up to thousands of kilometers .Fast or slow, abrupt or taking millions of years, uniformitarianism includes natural processes of all different rates, from abrupt and cataclysmic to barely detectable and very slow.Uniformtarianism does not require that all geological processes are slow.
Some are abrupt, such as an explosive volcanic eruption, an earthquake, or a landslide.
The combination of these two types of geologic ages makes a complete record of earth's geologic history in terms of the order of events and in terms of how many years ago each event occurred.
Relative geologic age refers to the order in which geologic events occurred.
Geologic time covers the whole sweep of earth's history, from how and when the earth first formed, to everything that has happened on, in, and to the planet since then, right up to now.
Geologists analyze geologic time in two different ways: in terms of relative geologic age, and in terms of absolute (or numeric) geologic age.
That means that tens of millions of years of geologic time lapsed between those two rock layers forming, and there is no sedimentary rock, no rock record, to record the details of what happened during that geologic time.