Radiopotassium dating

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.It can't float in mid-air, particularly if the material involved is sand, mud, or molten rock.

They are the "initial working hypotheses" to be tested further by data.

Using these principles, it is possible to construct an interpretation of the sequence of events for any geological situation, even on other planets (e.g., a crater impact can cut into an older, pre-existing surface, or craters may overlap, revealing their relative ages).

Most of these principles were formally proposed by Nicolaus Steno (Niels Steensen, Danish), in 1669, although some have an even older heritage that extends as far back as the authors of the Bible.

A few principles were recognized and specified later.

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.

An early summary of them is found in Charles Lyell's .

In no way are they meant to imply there are no exceptions.

Geochronologists do not claim that radiometric dating is foolproof (no scientific method is), but it does work reliably for most samples.

It is these highly consistent and reliable samples, rather than the tricky ones, that have to be falsified for "young Earth" theories to have any scientific plausibility, not to mention the need to falsify huge amounts of evidence from other techniques.

There are situations where it potentially fails -- for example, in cave deposits.

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