consolidating accounts examples - Radiation dating rocks

Over hundreds to thousands of millions of years, continents, oceans and mountain ranges have moved vast distances both vertically and horizontally.

For example, areas that were once deep oceans hundreds of millions of years ago are now mountainous desert regions.

By matching similar fossils in different regions throughout the world, correlations were built up over many years.

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The earliest geological time scales simply used the order of rocks laid down in a sedimentary rock sequence (stratum) with the oldest at the bottom.

However, a more powerful tool was the fossilised remains of ancient animals and plants within the rock strata.

Divisions in the geological time scales still use fossil evidence and mark major changes in the dominance of particular life forms.

For example, the Devonian Period is known as the 'Age of Fishes', as fish began to flourish at this stage.

It is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration.[8] Precision is enhanced if measurements are taken on multiple samples from different locations of the rock body.

Alternatively, if several different minerals can be dated from the same sample and are assumed to be formed by the same event and were in equilibrium with the reservoir when they formed, they should form an isochron. In uranium-lead dating, the concordia diagram is used which also decreases the problem of nuclide loss.

However, the end of the Devonian was marked by the predominance of a different life form, plants, which in turn denotes the beginning of the Carboniferous Period.

The different periods can be further subdivided (e.g.

principle sources: Australian Museum https://au/the-geological-time-scale Wikipedia https://en.wikipedia.org/wiki/Radiometric_dating Carleton University numerical (or "absolute") age is a specific number of years, like 150 million years ago.

A relative age simply states whether one rock formation is older or younger than another formation.

The basic equation of radiometric dating requires that neither the parent nuclide nor the daughter product can enter or leave the material after its formation.

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