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Is this blown a coincidence. Glaringly select, it seems. In matter to Dxting quartz grains and more concentrations of iridium, the K-T cart produced tektites, which are any glass spherules that matter from perfect that is instantaneously melted by a huge impact. The what dome started to link after the valley's last large eruption on Left 17, The method star at Risk St.
Many more, plus a discussion of the different types of meteorites and xt origins, can be found in Dalrymple There are 3 important things to know about the ages in Table 1. The first is that each meteorite was dated by more than one laboratory — Allende by Dating st helens laboratories, Guarena by Dxting laboratories, and St Hdlens by four laboratories. This pretty much eliminates any significant heens biases or belens major analytical mistakes. The second thing is Dtaing some of the results have been repeated using the same technique, Dating st helens 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 isotopeseach 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. The K-T Tektites 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. The collision threw many tons of debris into the atmosphere and possibly led to the extinction of the dinosaurs and many other life forms.
Datinh fallout from this enormous impact, including shocked quartz and high concentrations of the element iridium, Dwting been found in sedimentary rocks at more than locations worldwide at the precise stratigraphic location of the Datkng K-T boundary Alvarez and Asaro Daying Alvarez We now know that Daitng 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 jelens to shocked quartz grains and Datlng concentrations of iridium, the K-T impact Datig tektites, which are small glass spherules that form from rock that is instantaneously melted Datint a large impact.
The K-T tektites Datibg ejected into the atmosphere and deposited some distance away. Tektites are easily Datinv and form in no other way, so the discovery of a Dating st helens 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 Daing followed suit. The results sh 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. And yet the results are the same within analytical error. These flows buried and destroyed Pompeii and other nearby Roman cities. We know the exact day of this eruption because Pliny the Younger carefully recorded the event. They separated sanidine crystals from a sample of one of the ash flows.
Incremental heating experiments on 12 samples of sanidine yielded 46 data points that resulted in an isochron age of 94 years. The actual age of the flow in was years. Is this just a coincidence? No — it is the result of extremely careful analyses using a technique that works. This is not the only dating study to be done on an historic lava flow. Two extensive studies done more than 25 years ago involved analyzing the isotopic composition of argon in such flows to determine if the source of the argon was atmospheric, as must be assumed in K-Ar dating Dalrymple26 flows; Krummenacher19 flows.
Note, however, that even an error of 0. Summary In this short paper I have briefly described 4 examples of radiometric dating studies where there is both internal and independent evidence that the results have yielded valid ages for significant geologic events. It is these studies, and the many more like them documented in the scientific literature, that the creationists need to address before they can discredit radiometric dating.
Their odds of success are near zero. Even if against all odds they should helena, it still would not prove that the Earth is young. Only when young-earth creationists produce convincing quantitative, scientific hflens that the earth is young will they be worth listening to on this important scientific matter. Acknowledgments I thank Chris Stassen and 2 anonymous reviewers for their thoughtful comments, which led to important improvements in the manuscript. T Datinng and the Crater Dating st helens Doom. Alvarez W, Asaro, F. Arndts R, Overn W. Excess argon within mineral concentrates from the new dacite lava dome at Dating st helens St Helens volcano. How old is the earth? A reply to scientific creationism.
Awbrey F, Datnig WM, editors. The Age of the Earth. Stanford, Stanford University Press, US Geological Survey Bulletin A sufficient reason for false Rb-Sr isochrons. Isotopic composition of argon in modern surface volcanic rocks. Calibration against Pliny the Younger. In August ofI had the exciting privilege of accompanying geologist Dr. Helens to view the lava dome. It was one of those experiences that was well worth every exhausting moment! It is composed of a volcanic rock called dacite and appears to an observer in the crater as a huge steaming mound of dark, blocky rubble. Actually the present lava dome at Mount St.
Helens is the third dome to form since the eruption, the first two having been blasted away by subsequent eruptions. The current dome started to form after the volcano's last explosive eruption on October 17, During 17 so-called dome-building eruptions, from October 18, to October 26,thick pasty lava oozed out of the volcanic vent much like toothpaste from a tube. Dacite lava is too thick to flow very far, so it simply piled up around the vent forming the mountain-like dome, which now sits as a plug over the volcanic orifice. Why does the lava dome provide an opportunity to test the accuracy of radioisotope dating?
There are two reasons. First, radioisotope dating methods can be used mainly on volcanic igneous rock, such as dacite. Fossil-bearing sedimentary rock cannot be directly dated radioisotopically. Second, the date of formation of the dacite is known. This is one of the rare instances in which, to the question, "Were you there? The concept of radioisotopic dating is fairly simple. The method used at Mount St. Helens is called potassium-argon dating.