Why should the family of dr. Jose rizal strive to attain its noble objectives. Why do brussel sprouts turn pink in the middle you steam them then serve them with a lemon balsamic and a little olive oil sauce and they turn pink inside after a day or two. All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply. Why can't radioactive dating be used to date sedimentary rock?
There are three important things to note about these results.
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. 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.
Does radiometric dating work on sedimentary rocks
Many more, plus a discussion of the different types of meteorites and their origins, can be found in Dalrymple Table 1 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 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.
Because sedimentary rocks contain fragments of many rocks that could be different ages, radiometric dating is less useful for dating sedimentary . Sedimentary rocks cannot be dated directly using radiometric dating, which is based on the idea that when rocks are in liquid form, their radiometric clock resets. This technique is generally used to date igneous and metamorphic rock, which are rocks that were once melted due to extreme heat and pressure. 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.
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 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?
Radiometric or Absolute Rock Dating
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.
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. Table 2 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.
And yet the results are the same within analytical error. In the early afternoon of August 24, 79 CE, Mt Vesuvius erupted violently, sending hot ash flows speeding down its flanks.
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.
Both studies detected, in a few of the flows, deviations from atmospheric isotopic composition, most often in the form of excess 40 Ar. The majority of flows, however, had no detectable excess 40 Ar and thus gave correct ages as expected. Of the handful of flows that did contain excess 40 Ar, only a few did so in significant amounts.
Note, however, that even an error of 0. Austin has documented excess 40 Ar in the dacite flow from Mount St Helens, but the amounts are insufficient to produce significant errors in all but the youngest rocks. Thus any potential error due to excess 40 Ar was eliminated by the use of this technique, which was not available when the studies by Dalrymple and Krummenacher were done. Thus the large majority of historic lava flows that have been studied either give correct ages, as expected, or have quantities of excess radiogenic 40 Ar that would be insignificant in all but the youngest rocks.
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 succeed, it still would not prove that the Earth is young.
Only when young-earth creationists produce convincing quantitative, scientific evidence that the earth is young will they be worth listening to on this important scientific matter. I thank Chris Stassen and 2 anonymous reviewers for their thoughtful comments, which led to important improvements in the manuscript.
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The radiometric dating of suitable rocks (i.e. igneous or metamorphic) in proximity to their sedimentary counterparts, therefore allows the sedimentary rock to be dated as well. Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years. So in order to date most older fossils, scientists look for layers of igneous rock or volcanic ash above and below the fossil. Radiometric dating (often called radioactive dating) is a technique used to date materials such as rocks or carbon, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.
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This technique is primarily used to date igneous rocks. Asked in Science, Geology, Paleontology How do you see a sedimentary rocks age by looking at the fossils? Find out what era the Fossil was from and then you can put a relative date on the sedimentary rock, assuming that the fossil was preserved in the sedimentary rock when it had died.
It would not be the actual age because you need to date the radioactive isotopes for that. Asked in Geology Scientists date igneous rocks to indirectly date nearby sedimentary rocks Why doesn't radiometric dating typically work on sedimentary rocks? Sedimentary rocks contain bits of sediment, each much older than the rocks they form. Asked in Chemistry, Mining Why should you mine uranium?
Uranium is very useful for radioactive dating. It can date extremely old substances, and can date very accurately. Asked in Prehistoric Animals How do archaeologists date fossils?
Archaeologists dont date fossils they date artifacts now to stop correcting you Asked in Paleontology, Fossils What are dating method of fossils? Asked in Nuclear Physics How is the half-life used in radiometric dating? Radiometric dating often called radioactive dating is a technique used to date materials, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.
Asked in Fossils What are two ways geologists determine the age of fossils? Carbon dating and dating with other types of radioactive isotopes is the most common way to date an ancient object.
Asked in Geology, Paleontology, Fossils How can scientist use sedimentary rock to date fossils? More likely is the use of fossils to date sedimentary rock based on the index fossils which appear in it. The appearance of these index fossils indicates the geologic age in which they appeared.
This is called relative dating. Asked in Science Why is it difficult to dtermine the absolute age of a sedimentary rock? In most cases, all we have to date are the clasts in the sedimentary rock. Dating the clasts, however, would yield the age of the source rock from which they were derived rather than the current sedimentary rock. Asked in Physics, Paleontology, Archaeology How is radioactive decay used to date rocks? Radiometric dating uses the half-life of naturally occurring radioactive isotopes and their products to date rocks.
For example the half-life of uranium is 4. Half of the uranium will turn to lead. Asked in Geology, Paleontology, Fossils Which rock layer can you date by radioactive dating using half- life? Rock layers of igneous and some metamorphic rock that contain certain radioactive isotopes are datable by isotopic techniques. Asked in Paleontology, Radioactive Decay What kind of dating do you do in the lab?
For example, radioactive dating. Also, two people who work in a lab typically a man and a woman could have a date. Asked in Geology Why cant most sedimentary rocks be dated radiometrically?
Because most sedimentary rocks are composed of sediment which derived from many sources any dating process would find many different results.
For example, a zircon from a sedimentary rock may have been formed in an igneous rock many hundreds of millions of years before. Testing the zircon would give the date of the igneous rock, not the sedimentary.
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It is much safer to find the nearest contemporary igneous rock in the sequence and date that, even a thin layer of volcanic ash will do. Asked in Geology What are the two ways to date a fossil?
Radioactive isotope dating potassium, argon and relative dating, comparing with fossils of the same characteristics with known dates. Particularly if they are known to be 'zone fossils'. Asked in Geology, Paleontology, Fossils How does determining the ages of igneous rocks help to date fossils? Igneous intrusions that crosscut sedimentary rock that contain fossils can provide a date range because igneous rock is datable by radioactive decay techniques.