Distinguish between relative and radiometric dating

These are often characterised as the norm, rather than the exception.

I thought it would be useful to present an example where the geology is simple, and unsurprisingly, the method does work well, to show the quality of data that would have to be invalidated before a major revision of the geologic time scale could be accepted by conventional scientists.

his document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale.

It is not about the theory behind radiometric dating methods, it is about their , and it therefore assumes the reader has some familiarity with the technique already (refer to "Other Sources" for more information).

This orientation is not an assumption, because in virtually all situations, it is also possible to determine the original "way up" in the stratigraphic succession from "way up indicators".

For example, wave ripples have their pointed crests on the "up" side, and more rounded troughs on the "down" side.

The simplest situation for a geologist is a "layer cake" succession of sedimentary or extrusive igneous rock units arranged in nearly horizontal layers.

In such a situation, the "principle of superposition" is easily applied, and the strata towards the bottom are older, those towards the top are younger.

This document is partly based on a prior posting composed in reply to Ted Holden.

My thanks to both him and other critics for motivating me.

Much of the Earth's geology consists of successional layers of different rock types, piled one on top of another.

The most common rocks observed in this form are sedimentary rocks (derived from what were formerly sediments), and extrusive igneous rocks (e.g., lavas, volcanic ash, and other formerly molten rocks extruded onto the Earth's surface).

As an example of how they are used, radiometric dates from geologically simple, fossiliferous Cretaceous rocks in western North America are compared to the geological time scale.

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