We have even discredited entire techniques. For example, after extensive testing over many years, it was concluded that uranium-helium dating is highly unreliable because the small helium atom diffuses easily out of minerals over geologic time. As a result, this method is not used except in rare and highly specialized applications. These methods provide valuable and valid age data in most instances, although there is a small percentage of cases in which even these generally reliable methods yield incorrect results.
Such failures may be due to laboratory errors mistakes happen , unrecognized geologic factors nature sometimes fools us , or misapplication of the techniques no one is perfect. Not only that, they have to show the flaws in those dating studies that provide independent corroborative evidence that radiometric methods work. This is a tall order and the creationists have made no progress so far. It is rare for a study involving radiometric dating to contain a single determination of age.
Usually determinations of age are repeated to avoid laboratory errors, are obtained on more than one rock unit or more than one mineral from a rock unit in order to provide a cross-check, or are evaluated using other geologic information that can be used to test and corroborate the radiometric ages. Scientists who use radiometric dating typically use every means at their disposal to check, recheck, and verify their results, and the more important the results the more they are apt to be checked and rechecked by others. As a result, it is nearly impossible to be completely fooled by a good set of radiometric age data collected as part of a well-designed experiment.
The purpose of this paper is to describe briefly a few typical radiometric dating studies, out of hundreds of possible examples documented in the scientific literature, in which the ages are validated by other available information. I have selected four examples from recent literature, mostly studies involving my work and that of a few close colleagues because it was easy to do so.
I could have selected many more examples but then this would have turned into a book rather than the intended short paper. In the Cretaceous Period, a large meteorite struck the earth at a location near the present town of Manson, Iowa. The heat of the impact melted some of the feldspar crystals in the granitic rocks of the impact zone, thereby resetting their internal radiometric clocks. The impact also created shocked quartz crystals that were blasted into the air and subsequently fell to the west into the inland sea that occupied much of central North America at that time.
Today this shocked quartz is found in South Dakota, Colorado, and Nebraska in a thin layer the Crow Creek Member within a thick rock formation known as the Pierre Shale. The Pierre Shale, which is divided into identifiable sedimentary beds called members, also contains abundant fossils of numerous species of ammonites, ancestors of the chambered nautilus.
The fossils, when combined with geologic mapping, allow the various exposed sections of the Pierre Shale to be pieced together in their proper relative positions to form a complete composite section Figure 1. The Pierre Shale also contains volcanic ash that was erupted from volcanoes and then fell into the sea, where it was preserved as thin beds. There are three important things to note about these results.
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First, each age is based on numerous measurements; laboratory errors, had there been any, would be readily apparent. Second, ages were measured on two very different minerals, sanidine and biotite, from several of the ash beds. Third, the radiometric ages agree, within analytical error, with the relative positions of the dated ash beds as determined by the geologic mapping and the fossil assemblages; that is, the ages get older from top to bottom as they should.
Finally, the inferred age of the shocked quartz, as determined from the age of the melted feldspar in the Manson impact structure Meteorites, most of which are fragments of asteroids, are very interesting objects to study because they provide important evidence about the age, composition, and history of the early solar system. There are many types of meteorites. Some are from primitive asteroids whose material is little modified since they formed from the early solar nebula.
Others are from larger asteroids that got hot enough to melt and send lava flows to the surface.
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A few are even from the Moon and Mars. The most primitive type of meteorites are called chondrites, because they contain little spheres of olivine crystals known as chondrules. Because of their importance, meteorites have been extensively dated radiometrically; the vast majority appear to be 4.
Some meteorites, because of their mineralogy, can be dated by more than one radiometric dating technique, which provides scientists with a powerful check of the validity of the results. The results from three meteorites are shown in Table 1. Many more, plus a discussion of the different types of meteorites and their origins, can be found in Dalrymple There are 3 important things to know about the ages in Table 1.
Radiometric Dating Does Work!
The first is that each meteorite was dated by more than one laboratory — Allende by 2 laboratories, Guarena by 2 laboratories, and St Severin by four laboratories. This pretty much eliminates any significant laboratory biases or any major analytical mistakes. The second thing is that some of the results have been repeated using the same technique, which is another check against analytical errors.
The third is that all three meteorites were dated by more than one method — two methods each for Allende and Guarena, and four methods for St Severin. This is extremely powerful verification of the validity of both the theory and practice of radiometric dating. In the case of St Severin, for example, we have 4 different natural clocks actually 5, for the Pb-Pb method involves 2 different radioactive uranium isotopes , each running at a different rate and each using elements that respond to chemical and physical conditions in much different ways.
And yet, they all give the same result to within a few percent. Is this a remarkable coincidence? Scientists have concluded that it is not; it is instead a consequence of the fact that radiometric dating actually works and works quite well. Creationists who wants to dispute the conclusion that primitive meteorites, and therefore the solar system, are about 4. One of the most exciting and important scientific findings in decades was the discovery that a large asteroid, about 10 kilometers diameter, struck the earth at the end of the Cretaceous Period.
Radiometric Dating Does Work! | NCSE
The collision threw many tons of debris into the atmosphere and possibly led to the extinction of the dinosaurs and many other life forms. The fallout from this enormous impact, including shocked quartz and high concentrations of the element iridium, has been found in sedimentary rocks at more than locations worldwide at the precise stratigraphic location of the Cretaceous-Tertiary K-T boundary Alvarez and Asaro ; Alvarez We now know that the impact site is located on the Yucatan Peninsula.
Measuring the age of this impact event independently of the stratigraphic evidence is an obvious test for radiometric methods, and a number of scientists in laboratories around the world set to work. In addition to shocked quartz grains and high concentrations of iridium, the K-T impact produced tektites, which are small glass spherules that form from rock that is instantaneously melted by a large impact.
The K-T tektites were ejected into the atmosphere and deposited some distance away. Tektites are easily recognizable and form in no other way, so the discovery of a sedimentary bed the Beloc Formation in Haiti that contained tektites and that, from fossil evidence, coincided with the K-T boundary provided an obvious candidate for dating. Scientists from the US Geological Survey were the first to obtain radiometric ages for the tektites and laboratories in Berkeley, Stanford, Canada, and France soon followed suit.
The results from all of the laboratories were remarkably consistent with the measured ages ranging only from Similar tektites were also found in Mexico, and the Berkeley lab found that they were the same age as the Haiti tektites. The K-T boundary is recorded in numerous sedimentary beds around the world. Numerous thin beds of volcanic ash occur within these coals just centimeters above the K-T boundary, and some of these ash beds contain minerals that can be dated radiometrically.
Since both the ash beds and the tektites occur either at or very near the K-T boundary, as determined by diagnostic fossils, the tektites and the ash beds should be very nearly the same age, and they are Table 2. There are several important things to note about these results.
First, the Cretaceous and Tertiary periods were defined by geologists in the early s. The boundary between these periods the K-T boundary is marked by an abrupt change in fossils found in sedimentary rocks worldwide. Its exact location in the stratigraphic column at any locality has nothing to do with radiometric dating — it is located by careful study of the fossils and the rocks that contain them, and nothing more.
Furthermore, the dating was done in 6 different laboratories and the materials were collected from 5 different locations in the Western Hemisphere. Mafic microphenocrysts within these glassy particles were probably dominated by the strongly magnetic Fe-Ti oxide minerals.
The microscopic examination of the 'heavy-magnetic concentrate' also revealed a trace quantity of iron fragments, obviously the magnetic contaminant unavoidably introduced from the milling of the dacite in the iron mortar. No attempt was made to separate the hornblende from the Fe-Ti oxides, but further finer milling and use of heavy liquids should be considered. At this point Austin admits that the iron mortar probably contaminated his sample. Although the contamination might have seriously affected any iron analyses, K and Ar analyses may not have been affected.
The description of another one of Austin's 'fractions' indicates that it is also highly impure: These mafic microphenocrysts and fragments of mafic phenocrysts evidently increased the density of the attached glass particles above the critical density of 2. This sample also had recognizable hornblende, evidently not completely isolated by magnetic separation. Because it was composed of finer particles mesh , it contained far fewer mafic particles with attached glass fragments than DOME-IH. This preparation is the purest mineral concentrate. Therefore, instead of dating the ages of the pyroxenes, he probably dated a mixture of mostly pyroxenes along with other minerals and volcanic glass.
Again, a K-Ar date on such an impure 'fraction' would be meaningless and a waste of time and money. That is, Austin is not dating the volcanic glass or the pyroxenes in the dacite, but artificial mixtures, which result from incomplete separations. However, because Austin ignores the analytical inadequacies of Geochron's mass spectrometer hypothesis 2 , except for possibly the pyroxenes, there is no evidence that excess argon is present in any of the other mineral or glass components in this sample.
Because Austin admits that his separations were impure, how can he, Swenson and other YECs justify their claims that these dacite samples were a fair test of the validity of the K-Ar method? Why did Austin waste precious time and money analyzing samples that were known to contain mineral and glass impurities? As a geologist, Austin should have known that minerals, especially zoned minerals, take more time to crystallize than quenched disorder glass. How could he expect the relatively large and sometimes zoned minerals to be as young as the glass?!!
The following additional comments by Swenson demonstrate that he does not understand the mineralogy and chemistry of the dacite: However, Dalrymple  found that even volcanic glass can give wrong ages and rationalized that it can be contaminated by argon from older rock material. I should state that Swenson did not have the courtesy to name this critic it's me or cite even one of my sources that criticize Austin's efforts. In any debate, the debaters should provide the references or Internet links for their opponents so that the readers can evaluate both sides and really understand what's going on.
Clearly, Swenson simply assumes that the volcanic glass contains 'excess argon. In his essay, Austin even admits that the glass still needs to be separated and analyzed for argon. Furthermore, many studies for example, the Haulalai basalt; Funkhouser and Naughton, demonstrate that Swenson and other YECs cannot automatically assume that modern volcanic glass contains excess argon.
Although hypothesis 1 is plausible, until the argon isotope concentrations of the PURE glass are accurately measured for Austin's dacite if this is even possible we cannot properly evaluate this hypothesis. Because Swenson does not provide a page number for his citation of Dalrymple , the identity of the volcanic glass with excess argon is uncertain.
Perhaps, Swenson was referring to the following statement from Dalrymple , p. If Swenson is referring to this section, it's nothing more than an irrelevant red herring. Although high-pressure ocean water may prevent argon gas from escaping from the rims of a lava flow on the ocean floor, the centers of modern submarine flows typically provide K-Ar dates of 'zero years' Young, , p.
Because the centers of the flows cool more slowly, any excess 40Ar and other gases can disperse out of the remaining melt before solidification. While YECs explain geology by invoking talking snakes, magical fruit, and a mythical 'Flood', Dalrymple discusses legitimate chemistry and fluid physics, which is hardly relying on flimsy 'rationalizations' or implausible excuses.
Furthermore, contrary to Swenson's claims, nothing in Dalrymple excuses Austin's sloppy approach to K-Ar dating. In particular, YECs have no justification for automatically assuming that the dacite glass contains excess argon. Even if the dacite glass does contain excess argon, Dalrymple , p. That is, as the volcanics age, the excess argon would be diluted into insignificance by the developing radiogenic 40Ar.
Furthermore, if abundant excess argon is present in older rocks, Ar-Ar dating and K-Ar isochron dating can detect and eliminate its effects as examples, McDougall and Harrison, , p. Austin clearly believes that the ancient dates for his samples entirely resulted from excess argon hypothesis 1: Orthopyroxene retains the most argon, followed by hornblende, and finally, plagioclase.
It's certainly plausible that some excess argon could accumulate in small fractures or defects within the crystalline structures of pyroxenes, amphiboles, feldspars and other minerals Dickin, , p. While Austin claims that orthopyroxenes should retain the most argon followed by hornblende an amphibole and finally plagioclase, he provides no references to support this claim. In reality, the crystalline structures of amphiboles, unlike feldspars and pyroxenes, contain open channels, which can hold argon gas and other fluids Klein and Hurlbut, , p.
I'm skeptical that the defects and fractures in the orthopyroxenes and feldspars of Austin's dacites could hold more excess argon per mineral volume than the relatively large open structures within the hornblendes Dickin, , p. Therefore, IF hypothesis 1 was the only factor influencing the dates of Austin's samples, I would expect the hornblende-rich 'fraction' to provide an older date than the pyroxene- and feldspar-rich 'fractions.
From the above discussions, we already know that hypothesis 2 is a likely explanation for Austin's old dates. To evaluate hypothesis 3, we should look at the crystallization order of the phenocrysts as suggested by Bowen's Reaction Series. The series states that certain minerals will crystallize in a melt at higher temperatures than other minerals. That is, different minerals have different freezing points. Mafic magnesium and iron-rich volcanic rocks, such as basalts, form from relatively hot melts C and hotter, Hall, , p. Felsic silica-rich rocks, such as granites, form at cooler temperatures perhaps as cool as C , Hall, , p.
The most common minerals in rocks of intermediate chemistry, such as dacites, are located towards the middle of the series. Bowen's Reaction Series is a very important concept that undergraduate students learn in their introductory physical geology courses. To be exact, Bowen's Reaction Series was the one diagram that I was required to memorize when I took my first geology course in college. Although Bowen's Reaction Series was established long ago by field and laboratory studies, Swenson, Austin and other YECs repeatedly fail to comprehend its importance and how it can produce ancient phenocrysts, which may affect the radiometric dating of very young samples.
In a young volcanic rock, such as the Mt. Helen's dacite, the calcium-rich plagioclases may have formed thousands or even a few million years ago. Again, as a rock ages and 40Ar accumulates in both the glass and any 40K-bearing minerals, the differences in the ages of the materials becomes less significant. That is, if the glass quenched in an eruption , years after the formation of the calcium-rich plagioclases, after Bowen's Reaction Series also predicts that pyroxenes will crystallize at higher temperatures before amphiboles.
Assuming that any argon contamination from Geochron's equipment hypothesis 2 is negligible, we see that the dates in Austin's table are consistent with the crystallization order in Bowen's Reaction Series. As expected, the purest pyroxene fraction provides an older date 2. That is, IF the dates are real, the pyroxenes formed in the melt before the amphiboles as predicted by the series. Because the pyroxenes solidify before most other minerals, it's also not surprising that the 'pyroxene, etc.
Depending upon the amount of zoned feldspars which consist of older calcium-rich cores and younger sodium-rich rims and the quantity of glass, amphibole and pyroxene impurities, the 'feldspar etc. On the basis of the following statements by Swenson, his gross misinterpretations of Dalrymple , and his unwillingness to respond to my earlier statements on Bowen's Reaction Series and its possible relevance to Austin's results, it is clear that Swenson does not know what Bowen's Reaction Series is and how it can affect the age distributions of minerals in very young volcanic rocks: They said that Dr Austin should have known they were old because the crystals were large and zoned.
However, Dr Austin's results Table 1 show that the wrong ages were not confined to one particular mineral. The idea that the age of a mineral can be anticipated by its size or colour is incorrect. Dalrymple , for example, found that the wrong ages in his samples were unrelated to crystal size, or any other observable characteristic of the crystal. Contrary to Swenson's implications, mineral zoning is much more than a color property.
As discussed earlier, zoning and crystal growth are extremely important in understanding phenocryst ages. Based on the statements in his essays, Swenson simply assumes that excess argon is present in all of the components of the dacite and that any statements on the lack of a relationship between excess argon and crystal size in Dalrymple automatically apply to Austin's dacite. Again, because Swenson does not provide any page numbers when referring to Dalrymple , we can only guess which sections of Dalrymple's article he is citing.
The results for the Mt. Lassen plagioclase and the Mt. Etna flow, which contains a HIGH percentage of large phenocrysts, appear to support their contention. Thus, for THESE experiments there does not appear to be any correlation of excess 40Ar with large phenocrysts or with any other petrological or petrographic parameter. Clearly, whether amphibole, pyroxene, plagioclase or other phenocrysts are effectively degassed or not during eruptions is a complex and, perhaps, unpredictable issue. Nevertheless, as discussed in Dalrymple , p. Furthermore, if excess argon is relatively abundant in older samples, Ar-Ar dating and K-Ar isochron dating can detect and eliminate its effects as examples, McDougall and Harrison, , p.
They claim that these pieces of old rock xenoliths contaminated the sample and gave the very old age. In his report, Austin refers to the presence of 'lithic inclusions' in his samples. Helens lava dome is 'lithic inclusions': Although the mineral concentrates are not pure, and all contain some glass, an argument can be made that both mafic and non-mafic minerals of the dacite contain significant 40 Ar. The lithic inclusions in the lava dome might be thought to be the contaminant, in which case they might add "old" mafic and non-mafic minerals to the young magma.
It could be argued that gabbroic clumps in the magma disaggregated as the fluidity of the magma decreased with time, thereby adding an assortment of 'old' mineral grains. These inclusions are, therefore, regarded as a unique association within the recent magmatic system. Even IF 1 Austin's summation of Heliker is absolutely accurate and no gabbro xenoliths or xenoliths of any other lithologies were present in the dacite, 2 Austin succeeded in removing all of the 'lithic inclusions' from his samples as Swenson claims, 3 no microscopic xenocrysts were hiding in this messy dacite, and 4 hypothesis 2 was not a factor, Austin would still need to specify the lifespan of the 'recent magmatic system.
Sarfati's Support of Flood Geology. Again, Figure 4 by itself illustrates that ancient phenocrysts were present in the dacite, which would invalidate Austin's dates. Although Austin failed to properly fractionate and date the minerals and glass in Mt.
Mount St. Helens: a case against Evolution
Helens dacite, many scientists have been able to isolate specific minerals from older volcanics and successfully date them. Although xenocrysts and xenoliths are very common in the Peach Springs Tuff, Nielson et al. Unlike Austin, Nielson et al. Because Nielson et al.
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When confronted by Nielson et al. Even if excess argon is present in a sample, YECs must still explain the ultimate origin of 40Ar. The Earth's atmosphere currently contains relatively abundant concentrations of argon 0. Where did all of this argon come from if the Earth is only a few thousand years old? In nature, 40Ar is only known to originate from the radioactive decay of 40K. Some YECs might argue that the 40Ar could have come from the decay of another, unidentified isotope s. However, this is easier to say than to prove. Any advocates of unidentified parent isotopes need to identify these isotopes, produce any evidence of their former existence, and derive the appropriate decay reactions for them.
Other YECs might simply ignore the problem by saying that God created the 40Ar out of nothing 6, to 10, years ago. Again, this is an unproven fantasy and not science. Rather than invoking unproven miracles and plastering over the issue with 'God did it', scientists seek more profound, meaningful and useful natural answers.
Currently, the only reasonable explanation for the presence of abundant terrestrial 40Ar is that the Earth is ancient. Although the Sun is much larger than the Earth, silicates and 40K are more concentrated on Earth. The Sun mostly consists of hydrogen and helium, whereas the Earth has too little mass to retain large concentrations of these volatile elements. Instead, the relatively low mass of the Earth and its relatively close proximity to the Sun has resulted in silicon, potassium, iron and other less volatile elements concentrating in it.
Rather than dealing with this evidence, Austin simply states that the origin of the excess 40Ar requires 'more study'. In other words, YECs need more time to invent excuses to explain how abundant 40Ar could ever form on an Earth that is supposedly only 6, to 10, year old. Woodmorappe , Swenson, and other YECs frequently accuse geochronologists of 'rationalizing away' any anomalous radiometric dates.