Geologic time rock dating

07-May-2016 06:21

Geologists analyze geologic time in two different ways: in terms of relative geologic age, and in terms of absolute (or numeric) geologic age.

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.

They use absolute dating methods, sometimes called numerical dating, to give rocks an actual date, or date range, in number of years.

This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.

Some rocks and minerals can have their absolute age directly measured by analyzing the ratios of certain radioactive and non-radioactive isotopes they contain.

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.

Geologists often need to know the age of material that they find.

By using the principles of relative geologic age, the sequence of geologic events -- what happened first, what happened next, what happened last -- can be established.

Absolute geologic age refers to how long ago a geologic event occurred or a rock formed, in numeric terms, such as 65.5 million years ago.

Check out this video on the Uranium – Lead dating method: Biostratigraphy is a relative dating method that correlates rock ages using the fossils contained within rock units.

Long before geologists tried to quantify the age of the Earth they developed techniques to determine which geologic events preceded another, what are termed "relative age” relationships.

Geologists often need to know the age of material that they find.By using the principles of relative geologic age, the sequence of geologic events -- what happened first, what happened next, what happened last -- can be established.Absolute geologic age refers to how long ago a geologic event occurred or a rock formed, in numeric terms, such as 65.5 million years ago.Check out this video on the Uranium – Lead dating method: Biostratigraphy is a relative dating method that correlates rock ages using the fossils contained within rock units.Long before geologists tried to quantify the age of the Earth they developed techniques to determine which geologic events preceded another, what are termed "relative age” relationships.As minerals crystallise in igneous and metamorphic rocks they trap certain isotopes in their crystal structure that begin to decay radioactively as soon as the mineral forms.