Talk origins radiometric dating

How Old is the Earth: Radiometric Dating

talk origins radiometric dating

Claim CD Radiometric dating gives unreliable results. Radiometric dates are consistent with several nonradiometric dating methods. Radiometric dating falsely assumes that initial conditions are known, that none of the daughter components are in the mineral initially. Any tool will give bad results when misused. Radiocarbon dating has some known limitations. Any measurement that exceeds these limitations.

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This change also solved other problems that Morris complained about in his discussion of the K-Ar dating technique. These complaints were as follows: K-Ar dating techniques must be calibrated by uranium-lead U-Pb dating.

Some calibrations between U-Pb and K-Ar were done in the s and early s, but the decay rates of all the different radioisotopes involved are now known to within 1 percent, making the different dating techniques independent.

CD Carbon dating.

This has been demonstrated by the dating of chondrite meteorites Dalrymple and tektites and other ejecta and deposits created by the giant meteorite impact at Chicxulub in the Yucatan Peninsula Dalrymple et al.

The potassium-argon is an open system. The papers cited by Morris fail to probe this point. The first paper simply demonstrates that rock altered by weathering cannot be dated. The final paper claims potassium is quite mobile because potassium can be extracted from iron meteorites by using distilled water. However, K-Ar dating commonly uses potassium silicate minerals, which are very insoluble in water and resist weathering.

talk origins radiometric dating

Potassium cannot be significantly leached from the minerals used in K-Ar dating, or, conversely, the minerals from which significant potassium can be leached are not the minerals used in K-Ar dating. The decay rate of potassium is subject to change. This is simply not true. Argon maybe incorporated with potassium at time of formation.

See first point a above. K-Ar ages are extremely variable. The excess 40Ar content approaches zero toward pillow interiors, which cool more slowly and allow the 40Ar to escape, and in water depths of less than about meters because of the lessening of hydrostatic pressure. The purpose of these two studies was to determine, in a controlled experiment with samples of known age, the suitability of submarine pillow basalts for dating, because it was suspected that such samples might be unreliable.

Such studies are not unusual because each different type of mineral and rock has to be tested carefully before it can be used for any radiometric dating technique. In the case of the submarine pillow basalts, the results clearly indicated that these rocks are unsuitable for dating, and so they are not generally used for this purpose except in special circumstances and unless there is some independent way of verifying the results.

Turner, however, made no such comment about excess argon in lunar rocks, and there are no data in his report on which such a conclusion could be based. The statement by Rofahl and Segraves 77 is simply unjustifiable. The Flow from Hualalai Volcano Volcanic rocks produced by lava flows which occurred in Hawaii in the years were dated by the potassium-argon method. Excess argon produced apparent ages ranging from million to 2. The flow is unusual because it carries very abundant inclusions of rocks foreign to the lava.

These inclusions, called xenoliths meaning foreign rocksconsist primarily of olivine, a pale-green iron-magnesium silicate mineral. They come from deep within the mantle and were carried upward to the surface by the lava. 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 51 was on the xenoliths, not on the lava. The xenoliths, which vary in composition and range in size from single mineral grains to rocks as big as basketballs, do, indeed, carry excess argon in large amounts. Quite simply, xenoliths are one of the types of rocks that cannot be dated by the K-Ar technique.

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. Studies such as the one by Funkhouser and Naughton are routinely done to ascertain which materials are suitable for dating and which are not, and to determine the cause of sometimes strange results.

talk origins radiometric dating

They are part of a continuing effort to learn. Two extensive K-Ar studies on historical lava flows from around the world 3179 showed that excess argon is not a serious problem for dating lava flows. In nearly every case, the measured K-Ar age was zero, as expected if excess argon is uncommon. An exception is the lava from the Hualalai flow, which is so badly contaminated by the xenoliths that it is impossible to obtain a completely inclusion-free sample.

Initial 87Sr There is really no valid way of determining what the initial amounts of Sr87 in rocks were. As discussed above in the section on Rb-Sr dating the simplest form of Rb-Sr dating i. Such samples are rare, and so nearly all modern Rb-Sr dating is done by the isochron method. The beauty of the Rb-Sr isochron method is that knowledge of the initial Sr isotopic composition is not necessary — it is one of the results obtained.

A second advantage of the isochron method is that it contains internal checks on reliability. Look again at the isochron for the meteorite Juvinas Figure 3.

The data are straightforward albeit technically complex measurements that fall on a straight line, indicating that the meteorite has obeyed the closed-system requirement. The decay constants used in the calculations were the same as those in use throughout the world in The age of 4.

Initial 40Ar There is far too much Ar40 in the earth for more than a small fraction of it to have been formed by radioactive decay of K This is true even if the earth were really 4. In the atmosphere of the earth, Ar40 constitutes This is around times the amount that would be generated by radioactive decay over the hypothetical 4. Certainly this is not produced by an influx from outer space. Thus it would seem that a large amount of Ar40 was present in the beginning.

Since geochronologists assume that errors due to presence of initial Ar40 are small, their results are highly questionable. First, there is not more 40Ar in the atmosphere than can be accounted for by radioactive decay of 40K over 4. An amount of 40Ar equivalent to all the 40Ar now in the atmosphere could be generated in 4.

How Good Are Those Young-Earth Arguments?

Current estimates of the composition of the Earth indicate that the crust contains about 1. The 40Ar content of the atmosphere is well known and is 6. Thus, the Earth and the atmosphere now contain about equal amounts of 40Ar, and the total could be generated if the Earth contained only ppm potassium and released half of its 40Ar to the atmosphere.

Second, there have been sufficient tests to show that during their formation in the crust, igneous and metamorphic rocks nearly always release their entrapped 40Ar, thus resetting the K-Ar clock. In addition, scientists typically design their experiments so that anomalous results, such as might be caused by the rare case of initial 40Ar, are readily apparent.

The study of the Liberian diabase dikes, discussed above, is a good example of this practice. First, if it is assumed that there is a uniform distribution of Sr87 in the rock, then it is assumed that there is also a uniform distribution of Rb It only requires that the Sr isotopic composition, i. Even though the various minerals will incorporate different amounts of Sr as they cool and form, the Sr isotopic composition will be the same because natural processes do not significantly fractionate isotopes with so little mass difference as 87Sr and 86Sr.

Second, Slusher has confused isotopes and elements. Rb and Sr are quite different elements and are incorporated into the various minerals in varying proportions according to the composition and structure of the minerals. There is no way to correct for this natural isotopic variation since there is no way to determine it.

This renders the RbSr87 series useless as a clock. He has used an invalid analogy and come to an erroneous conclusion. Isochrons and Mixing Lines Arndts and Overn 8 and Kramer and others 78 claim that Rb-Sr isochrons are the result of mixing, rather than of decay of 87Rb over long periods: It is clear that mixing of pre-existent materials will yield a linear array of isotopic ratios.

talk origins radiometric dating

We need not assume that the isotopes, assumed to be daughter isotopes, were in fact produced in the rock by radioactive decay. The radioactive decay rates of nuclides used in radiometric dating have not been observed to vary since their rates were directly measurable, at least within limits of accuracy.

This is despite experiments that attempt to change decay rates Emery Extreme pressure can cause electron-capture decay rates to increase slightly less than 0.

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Supernovae are known to produce a large quantity of radioactive isotopes Nomoto et al. These isotopes produce gamma rays with frequencies and fading rates that are predictable according to present decay rates. Therefore, radioactive decay rates were not significantly differentyears ago.

Present decay rates are likewise consistent with observations of the gamma rays and fading rates of supernova SNT, which is sixty million light-years away Prantzosand with fading rate observations of supernovae billions of light-years away Perlmutter et al. The Oklo reactor was the site of a natural nuclear reaction 1, million years ago.

talk origins radiometric dating

The fine structure constant affects neutron capture rates, which can be measured from the reactor's products. These measurements show no detectable change in the fine structure constant and neutron capture for almost two billion years Fujii et al. Radioactive decay at a rate fast enough to permit a young earth would have produced enough heat to melt the earth Meert Different radioisotopes decay in different ways.

It is unlikely that a variable rate would affect all the different mechanisms in the same way and to the same extent.