Radiometric Dating: Methods, Uses & the Significance of Half-Life
It is not about the theory behind radiometric dating methods, it is about their applicationand it therefore assumes the reader has some familiarity with the technique already refer to "Other Sources" for more information. 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.
To get to that point, there is also a historical discussion and description of non-radiometric dating methods. The example used here contrasts sharply with the way conventional scientific dating methods are characterized by some critics for example, refer to discussion in " Common Creationist Criticisms of Mainstream Dating Methods " in the Age of the Ghosting while dating FAQ and Isochron Dating FAQ.
A relative and radiometric dating methods form of criticism is to cite geologically complicated situations daging the application of radiometric dating is very challenging. 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.
Geochronologists do not claim that radiometric dating is foolproof no scientific method isbut it does work reliably for most samples. It is these highly consistent and reliable samples, rather than the relative and radiometric dating methods 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 rqdiometric. 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 datihg 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 sedimentsand relative and radiometric dating methods igneous rocks e. The layers of rock are known as "strata", and the study of their succession is known as "stratigraphy". Fundamental to stratigraphy are a set of simple principles, based on elementary geometry, empirical observation of the way these rocks are deposited today, and gravity.
A few principles were recognized and specified later. An early summary of them is found in Charles Lyell's Principles of Geologypublished inand does not differ greatly from a modern formulation:. Note that these are principles. In no way are they meant to imply there are no exceptions. For example, the principle of superposition is based, fundamentally, on gravity.
In order for a layer of material to be deposited, something has to be beneath it to support it. It can't float in mid-air, particularly if the material involved is sand, mud, or molten rock. The principle of superposition therefore has a clear implication for the relative age of a vertical succession of strata. There are situations metthods it potentially fails -- for example, in cave deposits. In this situation, the cave contents are younger than both the bedrock below the cave and the suspended roof above.
Metohds, note rafiometric because of the " principle of cross-cutting relationships"careful examination of the dxting between the cave infill and the surrounding rock will reveal the true relative age relationships, as will the "principle of inclusion" if fragments of the surrounding rock are found within the infill. Cave deposits also often have distinctive structures of their own e.
These geological principles are not assumptions either. Each of them is a testable hypothesis about the relationships between rock units and their characteristics. They are applied by geologists in the same sense that a "null hypothesis" is in statistics -- not necessarily correct, just testable. In the last or more years of their application, they are often valid, but geologists do not assume they are. They are the "initial working hypotheses" to be tested further by data.
Using these principles, it is possible to datihg an interpretation of the sequence of events for any geological situation, even on other planets e. The simplest situation for a geologist is a "layer cake" succession of sedimentary or extrusive igneous rock units arranged in nearly horizontal va loan sewer hookup. In such a situation, the " principle of superposition" is easily applied, relative and radiometric dating methods the strata towards the bottom are older, those towards the top are younger.
For example, wave ripples have their pointed crests on the "up" side, and more rounded troughs on the "down" side. Many other indicators are commonly present, including ones that can even tell you the angle of the depositional surface at the time "geopetal structures""assuming" that gravity was "down" at the time, which isn't much of an assumption: In more complicated situations, like in a mountain belt, there are often faults, folds, and other structural complications that have deformed relatife "chopped up" the original stratigraphy.
Despite this, the "principle of cross cutting relationships" can be used to determine the sequence of deposition, folds, and faults based on their intersections relative and radiometric dating methods if folds and faults deform or cut across the sedimentary layers and surfaces, then they obviously came after deposition of the sediments. You can't deform a structure e. Tadiometric in complex situations of multiple deposition, deformation, erosion, deposition, and repeated events, it is possible to reconstruct the sequence of events.
Even if the folding is so intense that some of the strata is now upside down, this fact can be recognized with "way up" indicators. No matter what the geologic situation, these basic principles reliably yield a reconstructed history of the sequence of events, both depositional, erosional, deformational, and others, for the geology of a region. This reconstruction is tested and refined as new field information is collected, and can be and often is done completely independently of anything to do with other methods e.