Creation Science Rebuttals, Potassium-Argon Dating of Volcanics
Potassium-argon dating, method of determining the time of origin of rocks by measuring the ratio of radioactive argon to radioactive potassium in the rock. They taught me the inevitable hardness potassium argon dating accuracy potassium argon Home / k ar dating example potassium argon dating accuracy . May 15, Chronological Methods 9 - Potassium-Argon Dating By comparing the proportion of K to Ar in a sample of volcanic rock, and knowing.
In the field, they look like large raisins in a pudding, and even occur in beds piled one on top of the other, glued together by the lava. The study by Funkhouser and Naughton was on the xenoliths, not on the lava. The xenoliths, which vary in composition and range in size from single mineral grains to rocks the size of basketballs, do indeed carry excess argon in large amounts.
Funkhouser and Naughton were quite careful to point out that the apparent "ages" they measured were not geologically meaningful. Quite simply, xenoliths are one of the types of rocks that cannot be dated by K-Ar techniques. Funkhouser and Naughton were able to determine that the excess gas resides primarily in fluid bubbles in the minerals of the xenoliths, where it cannot escape upon reaching the surface.
Potassium-argon (K-Ar) dating
Studies such as the one by Funkhouser and Naughton are done to determine which materials are suitable for dating and which are not, and to determine the cause of sometimes strange results. They are part of the continuing effort to learn. There have been two extensive K-Ar studies on historic lava flows Dalrymple, ; Krummenacher, that showed that excess argon is not a serious problem for dating lava flows.
An exception is the lava from the Hualalei flow, which is so badly contaminated by the xenoliths that it is not possible to obtain a completely inclusion-free sample.
When rocks are heated to the melting point, any Ar contained in them is released into the atmosphere. When the rock recrystallizes it becomes impermeable to gasses again. As the K in the rock decays into Ar, the gas is trapped in the rock. The Decay Profile In this simulation, a unit of molten rock cools and crystallizes.
Argon Geochronology Methods
The ratio of K to Ar is plotted. Note that time is expressed in millions of years on this graph, as opposed to thousands of years in the C graph. Click on the "Show Movie" button below to view this animation. How are Samples Processed? Clicking on the "Show Movie" button below will bring up an animation that illustrates how a K-Ar sample is processed and the calculations involved in arriving at a date.
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- K/Ar Dating
This is actually a mini-simulator, in that it processes a different sample each time and generates different dates. K-Ar Processing Limitations on K-Ar Dating The Potassium-Argon dating method is an invaluable tool for those archaeologists and paleoanthropologists studying the earliest evidence for human evolution.
As with any dating technique, there are some significant limitations. The technique works well for almost any igneous or volcanic rock, provided that the rock gives no evidence of having gone through a heating-recrystallization process after its initial formation. For this reason, only trained geologists should collect the samples in the field. This technique is most useful to archaeologists and paleoanthropologists when lava flows or volcanic tuffs form strata that overlie strata bearing the evidence of human activity.
Dates obtained with this method then indicate that the archaeological materials cannot be younger than the tuff or lava stratum.