Radioactive Dating Game
The rest are said to be stable. There is no evidence of any of the half-lives changing over time. Layering of Elec-trical Conductivity. The chemical properties of rubidium and strontium are so dissimilar that minerals which readily accept rubidium into their crystal structure tend to exclude strontium and vice versa. Most of the members hold an old-Earth view, though membership is open to anyone supporting their positional statement. First, if it is assumed that there is a uniform distribution of Sr 87 in the rock, then it is assumed that there is also a uniform distribution of Rb Resources On the Web:
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The heavy isotope is lower in abundance during the colder winter snows than it is in snow falling in spring and summer. In fact, beryllium-7 is not used for dating rocks, as it has a half-life of only 54 days, and heavier atoms are even less subject to these minute changes, so the dates of rocks made by electron-capture decays would only be off by at most a few hundredths of a percent. Radioactive atoms used for dating have been subjected to extremes of heat, cold, pressure, vacuum, acceleration, and strong chemical reactions far beyond anything experienced by rocks, without any significant change. As the reader can easily see, the Rb-Sr isochron method is elegantly self-checking. Speaking from an extreme technical viewpoint this might be true--perhaps 1 atom out of 1,,,, of a certain isotope has leaked out of nearly all rocks, but such a change would make an immeasurably small change in the result.
Uncalibrated radiocarbon ages underestimate the actual ages. Note that a factor of two difference in the atmospheric carbon ratio, as shown in the top panel of Figure 9, does not translate to a factor of two offset in the age. Rather, the offset is equal to one half-life, or 5, years for carbon The initial portion of the calibration curve in Figure 9 has been widely available and well accepted for some time, so reported radiocarbon dates for ages up to 11, years generally give the calibrated ages unless otherwise stated.
The calibration curve over the portions extending to 40, years is relatively recent, but should become widely adopted as well. It is sometimes possible to date geologically young samples using some of the long-lived methods described above. These methods may work on young samples, for example, if there is a relatively high concentration of the parent isotope in the sample. In that case, sufficient daughter isotope amounts are produced in a relatively short time.
As an example, an article in Science magazine vol. There are other ways to date some geologically young samples. Besides the cosmogenic radionuclides discussed above, there is one other class of short-lived radionuclides on Earth. These are ones produced by decay of the long-lived radionuclides given in the upper part of Table 1. As mentioned in the Uranium-Lead section, uranium does not decay immediately to a stable isotope, but decays through a number of shorter-lived radioisotopes until it ends up as lead.
While the uranium-lead system can measure intervals in the millions of years generally without problems from the intermediate isotopes, those intermediate isotopes with the longest half-lives span long enough time intervals for dating events less than several hundred thousand years ago. Note that these intervals are well under a tenth of a percent of the half-lives of the long-lived parent uranium and thorium isotopes discussed earlier. Two of the most frequently-used of these "uranium-series" systems are uranium and thorium These are listed as the last two entries in Table 1, and are illustrated in Figure A schematic representation of the uranium decay chain, showing the longest-lived nuclides.
Half-lives are given in each box. Solid arrows represent direct decay, while dashed arrows indicate that there are one or more intermediate decays, with the longest intervening half-life given below the arrow.
Like carbon, the shorter-lived uranium-series isotopes are constantly being replenished, in this case, by decaying uranium supplied to the Earth during its original creation. Following the example of carbon, you may guess that one way to use these isotopes for dating is to remove them from their source of replenishment.
This starts the dating clock. In carbon this happens when a living thing like a tree dies and no longer takes in carbonladen CO 2. For the shorter-lived uranium-series radionuclides, there needs to be a physical removal from uranium. The chemistry of uranium and thorium are such that they are in fact easily removed from each other.
Uranium tends to stay dissolved in water, but thorium is insoluble in water. So a number of applications of the thorium method are based on this chemical partition between uranium and thorium. Sediments at the bottom of the ocean have very little uranium relative to the thorium. Because of this, the uranium, and its contribution to the thorium abundance, can in many cases be ignored in sediments.
Thorium then behaves similarly to the long-lived parent isotopes we discussed earlier. It acts like a simple parent-daughter system, and it can be used to date sediments. On the other hand, calcium carbonates produced biologically such as in corals, shells, teeth, and bones take in small amounts of uranium, but essentially no thorium because of its much lower concentrations in the water.
This allows the dating of these materials by their lack of thorium. A brand-new coral reef will have essentially no thorium As it ages, some of its uranium decays to thorium While the thorium itself is radioactive, this can be corrected for. Comparison of uranium ages with ages obtained by counting annual growth bands of corals proves that the technique is. The method has also been used to date stalactites and stalagmites from caves, already mentioned in connection with long-term calibration of the radiocarbon method.
In fact, tens of thousands of uranium-series dates have been performed on cave formations around the world. Previously, dating of anthropology sites had to rely on dating of geologic layers above and below the artifacts. But with improvements in this method, it is becoming possible to date the human and animal remains themselves. Work to date shows that dating of tooth enamel can be quite reliable. However, dating of bones can be more problematic, as bones are more susceptible to contamination by the surrounding soils.
As with all dating, the agreement of two or more methods is highly recommended for confirmation of a measurement. If the samples are beyond the range of radiocarbon e.
We will digress briefly from radiometric dating to talk about other dating techniques. It is important to understand that a very large number of accurate dates covering the past , years has been obtained from many other methods besides radiometric dating. We have already mentioned dendrochronology tree ring dating above.
Dendrochronology is only the tip of the iceberg in terms of non-radiometric dating methods. Here we will look briefly at some other non-radiometric dating techniques.
One of the best ways to measure farther back in time than tree rings is by using the seasonal variations in polar ice from Greenland and Antarctica.
There are a number of differences between snow layers made in winter and those made in spring, summer, and fall. These seasonal layers can be counted just like tree rings. The seasonal differences consist of a visual differences caused by increased bubbles and larger crystal size from summer ice compared to winter ice, b dust layers deposited each summer, c nitric acid concentrations, measured by electrical conductivity of the ice, d chemistry of contaminants in the ice, and e seasonal variations in the relative amounts of heavy hydrogen deuterium and heavy oxygen oxygen in the ice.
These isotope ratios are sensitive to the temperature at the time they fell as snow from the clouds. The heavy isotope is lower in abundance during the colder winter snows than it is in snow falling in spring and summer. So the yearly layers of ice can be tracked by each of these five different indicators, similar to growth rings on trees. The different types of layers are summarized in Table III.
Ice cores are obtained by drilling very deep holes in the ice caps on Greenland and Antarctica with specialized drilling rigs. As the rigs drill down, the drill bits cut around a portion of the ice, capturing a long undisturbed "core" in the process.
These cores are carefully brought back to the surface in sections, where they are catalogued, and taken to research laboratories under refrigeration. A very large amount of work has been done on several deep ice cores up to 9, feet in depth.
Several hundred thousand measurements are sometimes made for a single technique on a single ice core. A continuous count of layers exists back as far as , years.
In addition to yearly layering, individual strong events such as large-scale volcanic eruptions can be observed and correlated between ice cores. A number of historical eruptions as far back as Vesuvius nearly 2, years ago serve as benchmarks with which to determine the accuracy of the yearly layers as far down as around meters.
As one goes further down in the ice core, the ice becomes more compacted than near the surface, and individual yearly layers are slightly more difficult to observe.
For this reason, there is some uncertainty as one goes back towards , years. Recently, absolute ages have been determined to 75, years for at least one location using cosmogenic radionuclides chlorine and beryllium G.
These agree with the ice flow models and the yearly layer counts. Note that there is no indication anywhere that these ice caps were ever covered by a large body of water, as some people with young-Earth views would expect. Polar ice core layers, counting back yearly layers, consist of the following:. Visual Layers Summer ice has more bubbles and larger crystal sizes Observed to 60, years ago Dust Layers Measured by laser light scattering; most dust is deposited during spring and summer Observed to , years ago Layering of Elec-trical Conductivity Nitric acid from the stratosphere is deposited in the springtime, and causes a yearly layer in electrical conductivity measurement Observed through 60, years ago Contaminant Chemistry Layers Soot from summer forest fires, chemistry of dust, occasional volcanic ash Observed through 2, years; some older eruptions noted Hydrogen and Oxygen Isotope Layering Indicates temperature of precipitation.
Heavy isotopes oxygen and deuterium are depleted more in winter. Yearly layers observed through 1, years; Trends observed much farther back in time Varves. Another layering technique uses seasonal variations in sedimentary layers deposited underwater. The two requirements for varves to be useful in dating are 1 that sediments vary in character through the seasons to produce a visible yearly pattern, and 2 that the lake bottom not be disturbed after the layers are deposited. These conditions are most often met in small, relatively deep lakes at mid to high latitudes.
Shallower lakes typically experience an overturn in which the warmer water sinks to the bottom as winter approaches, but deeper lakes can have persistently thermally stratified temperature-layered water masses, leading to less turbulence, and better conditions for varve layers.
Varves can be harvested by coring drills, somewhat similar to the harvesting of ice cores discussed above. Overall, many hundreds of lakes have been studied for their varve patterns. Each yearly varve layer consists of a mineral matter brought in by swollen streams in the spring. Regular sequences of varves have been measured going back to about 35, years. The thicknesses of the layers and the types of material in them tells a lot about the climate of the time when the layers were deposited.
For example, pollens entrained in the layers can tell what types of plants were growing nearby at a particular time. Other annual layering methods. Besides tree rings, ice cores, and sediment varves, there are other processes that result in yearly layers that can be counted to determine an age.
Annual layering in coral reefs can be used to date sections of coral. Coral generally grows at rates of around 1 cm per year, and these layers are easily visible. As was mentioned in the uranium-series section, the counting of annual coral layers was used to verify the accuracy of the thorium method. There is a way of dating minerals and pottery that does not rely directly on half-lives. Thermoluminescence dating, or TL dating, uses the fact that radioactive decays cause some electrons in a material to end up stuck in higher-energy orbits.
The number of electrons in higher-energy orbits accumulates as a material experiences more natural radioactivity over time. If the material is heated, these electrons can fall back to their original orbits, emitting a very tiny amount of light. If the heating occurs in a laboratory furnace equipped with a very sensitive light detector, this light can be recorded. The term comes from putting together thermo , meaning heat, and luminescence , meaning to emit light.
By comparison of the amount of light emitted with the natural radioactivity rate the sample experienced, the age of the sample can be determined. TL dating can generally be used on samples less than half a million years old. TL dating and its related techniques have been cross calibrated with samples of known historical age and with radiocarbon and thorium dating. While TL dating does not usually pinpoint the age with as great an accuracy as these other conventional radiometric dating, it is most useful for applications such as pottery or fine-grained volcanic dust, where other dating methods do not work as well.
Electron spin resonance ESR. Also called electron paramagnetic resonance, ESR dating also relies on the changes in electron orbits and spins caused by radioactivity over time. However, ESR dating can be used over longer time periods, up to two million years, and works best on carbonates, such as in coral reefs and cave deposits. It has also seen extensive use in dating tooth enamel. This dating method relies on measuring certain isotopes produced by cosmic ray impacts on exposed rock surfaces.
Because cosmic rays constantly bombard meteorites flying through space, this method has long been used to date the ' flight time' of meteorites--that is the time from when they were chipped off a larger body like an asteroid to the time they land on Earth.
The cosmic rays produce small amounts of naturally-rare isotopes such as neon and helium-3, which can be measured in the laboratory. The cosmic-ray exposure ages of meteorites are usually around 10 million years, but can be up to a billion years for some iron meteorites. In the last fifteen years, people have also used cosmic ray exposure ages to date rock surfaces on the Earth. This is much more complicated because the Earth's magnetic field and atmosphere shield us from most of the cosmic rays.
Cosmic ray exposure calibrations must take into. Nevertheless, terrestrial cosmic-ray exposure dating has been shown to be useful in many cases. We have covered a lot of convincing evidence that the Earth was created a very long time ago. The agreement of many different dating methods, both radiometric and non-radiometric, over hundreds of thousands of samples, is very convincing.
Yet, some Christians question whether we can believe something so far back in the past. My answer is that it is similar to believing in other things of the past. It only differs in degree. Why do you believe Abraham Lincoln ever lived? Because it would take an extremely elaborate scheme to make up his existence, including forgeries, fake photos, and many other things, and besides, there is no good reason to simply have made him up.
Well, the situation is very similar for the dating of rocks, only we have rock records rather than historical records. The last three points deserve more attention. Some Christians have argued that something may be slowly changing with time so all the ages look older than they really are.
The only two quantities in the exponent of a decay rate equation are the half-life and the time. So for ages to appear longer than actual, all the half-lives would have to be changing in sync with each other. One could consider that time itself was changing if that happened remember that our clocks are now standardized to atomic clocks! Beyond this, scientists have now used a "time machine" to prove that the half-lives of radioactive species were the same millions of years ago.
This time machine does not allow people to actually go back in time, but it does allow scientists to observe ancient events from a long way away. The time machine is called the telescope. Because God's universe is so large, images from distant events take a long time to get to us. Telescopes allow us to see supernovae exploding stars at distances so vast that the pictures take hundreds of thousands to millions of years to arrive at the Earth. So the events we see today actually occurred hundreds of thousands to millions of years ago.
And what do we see when we look back in time? Much of the light following a supernova blast is powered by newly created radioactive parents. So we observe radiometric decay in the supernova light. The half-lives of decays occurring hundreds of thousands of years ago are thus carefully recorded! These half-lives completely agree with the half-lives measured from decays occurring today.
We must conclude that all evidence points towards unchanging radioactive half-lives. Some individuals have suggested that the speed of light must have been different in the past, and that the starlight has not really taken so long to reach us. However, the astronomical evidence mentioned above also suggests that the speed of light has not changed, or else we would see a significant apparent change in the half-lives of these ancient radioactive decays. Some doubters have tried to dismiss geologic dating with a sleight of hand by saying that no rocks are completely closed systems that is, that no rocks are so isolated from their surroundings that they have not lost or gained some of the isotopes used for dating.
Speaking from an extreme technical viewpoint this might be true--perhaps 1 atom out of 1,,,, of a certain isotope has leaked out of nearly all rocks, but such a change would make an immeasurably small change in the result.
The real question to ask is, "is the rock sufficiently close to a closed system that the results will be same as a really closed system? These books detail experiments showing, for a given dating system, which minerals work all of the time, which minerals work under some certain conditions, and which minerals are likely to lose atoms and give incorrect results.
Understanding these conditions is part of the science of geology. Geologists are careful to use the most reliable methods whenever possible, and as discussed above, to test for agreement between different methods. Some people have tried to defend a young Earth position by saying that the half-lives of radionuclides can in fact be changed, and that this can be done by certain little-understood particles such as neutrinos, muons, or cosmic rays.
This is stretching it. While certain particles can cause nuclear changes, they do not change the half-lives. The nuclear changes are well understood and are nearly always very minor in rocks. In fact the main nuclear changes in rocks are the very radioactive decays we are talking about.
There are only three quite technical instances where a half-life changes, and these do not affect the dating methods we have discussed. Only one technical exception occurs under terrestrial conditions, and this is not for an isotope used for dating. According to theory, electron-capture is the most likely type of decay to show changes with pressure or chemical combination, and this should be most pronounced for very light elements.
The artificially-produced isotope, beryllium-7 has been shown to change by up to 1. In another experiment, a half-life change of a small fraction of a percent was detected when beryllium-7 was subjected to , atmospheres of pressure, equivalent to depths greater than miles inside the Earth Science , , All known rocks, with the possible exception of diamonds, are from much shallower depths.
In fact, beryllium-7 is not used for dating rocks, as it has a half-life of only 54 days, and heavier atoms are even less subject to these minute changes, so the dates of rocks made by electron-capture decays would only be off by at most a few hundredths of a percent. Physical conditions at the center of stars or for cosmic rays differ very greatly from anything experienced in rocks on or in the Earth. Yet, self-proclaimed "experts" often confuse these conditions. Cosmic rays are very, very high-energy atomic nuclei flying through space.
The electron-capture decay mentioned above does not take place in cosmic rays until they slow down. This is because the fast-moving cosmic ray nuclei do not have electrons surrounding them, which are necessary for this form of decay.
Another case is material inside of stars, which is in a plasma state where electrons are not bound to atoms. In the extremely hot stellar environment, a completely different kind of decay can occur. This has been observed for dysprosium and rhenium under very specialized conditions simulating the interior of stars Phys.
All normal matter, such as everything on Earth, the Moon, meteorites, etc. As an example of incorrect application of these conditions to dating, one young-Earth proponent suggested that God used plasma conditions when He created the Earth a few thousand years ago. This writer suggested that the rapid decay rate of rhenium under extreme plasma conditions might explain why rocks give very old ages instead of a young-Earth age.
This writer neglected a number of things, including: More importantly, b rocks and hot gaseous plasmas are completely incompatible forms of matter!
The material would have to revert back from the plasma state before it could form rocks. In such a scenario, as the rocks cooled and hardened, their ages would be completely reset to zero as described in previous sections.
That is obviously not what is observed. The last case also involves very fast-moving matter. It has been demonstrated by atomic clocks in very fast spacecraft. These atomic clocks slow down very slightly only a second or so per year as predicted by Einstein's theory of relativity. No rocks in our solar system are going fast enough to make a noticeable change in their dates.
These cases are very specialized, and all are well understood. None of these cases alter the dates of rocks either on Earth or other planets in the solar system. The conclusion once again is that half-lives are completely reliable in every context for the dating of rocks on Earth and even on other planets. The Earth and all creation appears to be very ancient.
It would not be inconsistent with the scientific evidence to conclude that God made everything relatively recently, but with the appearance of great age, just as Genesis 1 and 2 tell of God making Adam as a fully grown human which implies the appearance of age. This idea was captured by Phillip Henry Gosse in the book, " Omphalos: The idea of a false appearance of great age is a philosophical and theological matter that we won't go into here.
The main drawback--and it is a strong one--is that this makes God appear to be a deceiver. Certainly whole civilizations have been incorrect deceived? Whatever the philosophical conclusions, it is important to note that an apparent old Earth is consistent with the great amount of scientific evidence. As Christians it is of great importance that we understand God's word correctly. Yet from the middle ages up until the s people insisted that the Bible taught that the Earth, not the Sun, was the center of the solar system.
It wasn't that people just thought it had to be that way; they actually quoted scriptures: I am afraid the debate over the age of the Earth has many similarities. But I am optimistic.
Today there are many Christians who accept the reliability of geologic dating, but do not compromise the spiritual and historical inerrancy of God's word. While a full discussion of Genesis 1 is not given here, references are given below to a few books that deal with that issue. There are a number of misconceptions that seem especially prevalent among Christians. Most of these topics are covered in the above discussion, but they are reviewed briefly here for clarity.
Radiometric dating is based on index fossils whose dates were assigned long before radioactivity was discovered. This is not at all true, though it is implied by some young-Earth literature.
Radiometric dating is based on the half-lives of the radioactive isotopes. These half-lives have been measured over the last years. They are not calibrated by fossils. No one has measured the decay rates directly; we only know them from inference. Decay rates have been directly measured over the last years. In some cases a batch of the pure parent material is weighed and then set aside for a long time and then the resulting daughter material is weighed.
In many cases it is easier to detect radioactive decays by the energy burst that each decay gives off. For this a batch of the pure parent material is carefully weighed and then put in front of a Geiger counter or gamma-ray detector.
These instruments count the number of decays over a long time. If the half-lives are billions of years, it is impossible to determine them from measuring over just a few years or decades. The example given in the section titled, "The Radiometric Clocks" shows that an accurate determination of the half-life is easily achieved by direct counting of decays over a decade or shorter. This is because a all decay curves have exactly the same shape Fig.
Additionally, lavas of historically known ages have been correctly dated even using methods with long half-lives. Most of the decay rates used for dating rocks are known to within two percent. Such small uncertainties are no reason to dismiss radiometric dating. Whether a rock is million years or million years old does not make a great deal of difference. A small error in the half-lives leads to a very large error in the date. Since exponents are used in the dating equations, it is possible for people to think this might be true, but it is not.
This is not true in the context of dating rocks. Radioactive atoms used for dating have been subjected to extremes of heat, cold, pressure, vacuum, acceleration, and strong chemical reactions far beyond anything experienced by rocks, without any significant change.
The only exceptions, which are not relevant to dating rocks, are discussed under the section, "Doubters Still Try", above. A small change in the nuclear forces probably accelerated nuclear clocks during the first day of creation a few thousand years ago, causing the spuriously old radiometric dates of rocks. Rocks are dated from the time of their formation. For it to have any bearing on the radiometric dates of rocks, such a change of nuclear forces must have occurred after the Earth and the rocks were formed.
To make the kind of difference suggested by young-Earth proponents, the half-lives must be shortened from several billion years down to several thousand years--a factor of at least a million. But to shorten half-lives by factors of a million would cause large physical changes. As one small example, recall that the Earth is heated substantially by radioactive decay. If that decay is speeded up by a factor of a million or so, the tremendous heat pulse would easily melt the whole Earth , including the rocks in question!
No radiometric ages would appear old if this happened. The decay rates might be slowing down over time, leading to incorrect old dates. There are two ways we know this didn't happen: We should measure the "full-life" the time at which all of the parent is gone rather than the half-life the time when half of it is gone. Unlike sand in an hourglass, which drops at a constant rate independent of how much remains in the top half of the glass, the number of radioactive decays is proportional to the amount of parent remaining.
A half-life is more easy to define than some point at which almost all of the parent is gone. Scientists sometimes instead use the term "mean life", that is, the average life of a parent atom. For most of us half-life is easier to understand.
To date a rock one must know the original amount of the parent element. But there is no way to measure how much parent element was originally there. It is very easy to calculate the original parent abundance, but that information is not needed to date the rock.
All of the dating schemes work from knowing the present abundances of the parent and daughter isotopes. There is little or no way to tell how much of the decay product, that is, the daughter isotope, was originally in the rock, leading to anomalously old ages.
A good part of this article is devoted to explaining how one can tell how much of a given element or isotope was originally present. Usually it involves using more than one sample from a given rock. It is done by comparing the ratios of parent and daughter isotopes relative to a stable isotope for samples with different relative amounts of the parent isotope. From this one can determine how much of the daughter isotope would be present if there had been no parent isotope.
This is the same as the initial amount it would not change if there were no parent isotope to decay. Figures 4 and 5, and the accompanying explanation, tell how this is done most of the time.
This article has listed and discussed a number of different radiometric dating methods and has also briefly described a number of non-radiometric dating methods. There are actually many more methods out there. Well over forty different radiometric dating methods are in use, and a number of non-radiogenic methods not even mentioned here.
This refers to tiny halos of crystal damage surrounding spots where radioactive elements are concentrated in certain rocks. Halos thought to be from polonium, a short-lived element produced from the decay of uranium, have been found in some rocks.
A plausible explanation for a halo from such a short-lived element is that these were not produced by an initial concentration of the radioactive element. Rather, as water seeped through cracks in the minerals, a chemical change caused newly-formed polonium to drop out of solution at a certain place and almost immediately decay there.
A halo would build up over a long period of time even though the center of the halo never contained more than a few atoms of polonium at one time. Other researchers have found halos produced by an indirect radioactive decay effect called hole diffusion, which is an electrical effect in a crystal.
These results suggest that the halos in question are not from short-lived isotopes after all. At any rate, halos from uranium inclusions are far more common. Because of uranium's long half-lives, these halos take at least several hundred million years to form. Because of this, most people agree that halos provide compelling evidence for a very old Earth.
A young-Earth research group reported that they sent a rock erupted in from Mount Saint Helens volcano to a dating lab and got back a potassium-argon age of several million years. This shows we should not trust radiometric dating.
There are indeed ways to "trick" radiometric dating if a single dating method is improperly used on a sample. Anyone can move the hands on a clock and get the wrong time. Likewise, people actively looking for incorrect radiometric dates can in fact get them.
Geologists have known for over forty years that the potassium-argon method cannot be used on rocks only twenty to thirty years old. Publicizing this incorrect age as a completely new finding was inappropriate. The reasons are discussed in the Potassium-Argon Dating section above. Be assured that multiple dating methods used together on igneous rocks are almost always correct unless the sample is too difficult to date due to factors such as metamorphism or a large fraction of xenoliths.
Low abundances of helium in zircon grains show that these minerals are much younger than radiometric dating suggests. Zircon grains are important for uranium-thorium-lead dating because they contain abundant uranium and thorium parent isotopes. Helium is also produced from the decay of uranium and thorium. However, as a gas of very small atomic size, helium tends to escape rather easily. Researchers have studied the rates of diffusion of helium from zircons, with the prediction from one study by a young- Earth creationist suggesting that it should be quantitatively retained despite its atomic size.
The assumptions of the temperature conditions of the rock over time are most likely unrealistic in this case. The fact that radiogenic helium and argon are still degassing from the Earth's interior prove that the Earth must be young.
The radioactive parent isotopes, uranium and potassium, have very long half-lives, as shown in Table 1. These parents still exist in abundance in the Earth's interior, and are still producing helium and argon. There is also a time lag between the production of the daughter products and their degassing.
If the Earth were geologically very young, very little helium and argon would have been produced. One can compare the amount of argon in the atmosphere to what would be expected from decay of potassium over 4.
The waters of Noah's flood could have leached radioactive isotopes out of rocks, disturbing their ages. This is actually suggested on one website! While water can affect the ability to date rock surfaces or other weathered areas, there is generally no trouble dating interior portions of most rocks from the bottom of lakes, rivers, and oceans. Additionally, if ages were disturbed by leaching, the leaching would affect different isotopes at vastly different rates. Ages determined by different methods would be in violent disagreement.
If the flood were global in scope, why then would we have any rocks for which a number of different methods all agree with each other? In fact, close agreement between methods for most samples is a hallmark of radiometric dating. We know the Earth is much younger because of non-radiogenic indicators such as the sedimentation rate of the oceans. There are a number of parameters which, if extrapolated from the present without taking into account the changes in the Earth over time, would seem to suggest a somewhat younger Earth.
These arguments can sound good on a very simple level, but do not hold water when all the factors are considered. Some examples of these categories are the decaying magnetic field not mentioning the widespread evidence for magnetic reversals , the saltiness of the oceans not counting sedimentation! While these arguments do not stand up when the complete picture is considered, the case for a very old creation of the Earth fits well in all areas considered.
The fact is that there are a number of Bible-believing Christians who are involved in radiometric dating, and who can see its validity firsthand. A great number of other Christians are firmly convinced that radiometric dating shows evidence that God created the Earth billions, not thousands, of years ago.
This is not true at all. The fact that dating techniques most often agree with each other is why scientists tend to trust them in the first place.
Nearly every college and university library in the country has periodicals such as Science , Nature , and specific geology journals that give the results of dating studies. The public is usually welcome to and should! So the results are not hidden; people can go look at the results for themselves. Over a thousand research papers are published a year on radiometric dating, essentially all in agreement. Besides the scientific periodicals that carry up-to-date research reports, specific suggestions are given below for further reading, both for textbooks, non-classroom books, and web resources.
Resources On the Web: Virtual Dating--a very helpful educational course on half-lives and radioactive decay was put together by Gary Novak at California State University in Los Angeles.
This site has several interactive web "workbooks" to help the reader understand various concepts involved with radiometricdating.
Reasons to Believe--a Christian ministry supporting the old-Earth viewpoint. Hugh Ross, the founder and head of the ministry, holds a PhD in Astronomy. The ministry supports an accurate interpretation of the Bible while also supportive of science as a tool to study God's creation. Most of the members hold an old-Earth view, though membership is open to anyone supporting their positional statement. This website has numerous resources on theology and Bible-science issues.
There is a wealth of information, including presentations on the interpretation of Genesis chapters , a resource list of apologetics ministries, etc. A review of Phillip Henry Gosse's Omphalos: An Attempt to Untie the Geological Knot , in which fiat creation with the appearance of age is suggested. Origins--this site is devoted mainly to evidences for intelligent design in nature. Talk Origins--an archive dedicated to creation-evolution issues. It includes separate resource sections on the reliability of radiometric dating, introductory articles, advanced articles, radiocarbon dating, etc.
C Dating--The radiocarbon laboratories at Oxford England and Waikato New Zealand Universities jointly operate this website which gives very comprehensive information on radiocarbon dating. Portions of it were written specifically for use by K students, so it is easy to understand. The site contains explanations on measurements, applications, calibration, publications, and other areas. Cornell University Geology Lecture Notes--A large number of pdf files of geology lecture notes are available on the web.
These are university-level lecture notes describing radiometric dating and related topics. The following books are popular college-level Geology texts that deal in depth with various dating techniques.
Geologic Time is very easy to read and has been around for quite some time. The text by Dalrymple is meant to be relatively easy to read, but is also very comprehensive. The Faure and Dickin texts are regular textbooks for Geology, including more mathematics and more details. Cambridge University Press, pp. Brent The Age of the Earth. Stanford University Press, pp.
AComprehensive Textbook for Geology Students. Faure, Gunter Principles of Isotope Geology , 2nd edition. Wiley, New York, pp. Atheneum Books, New York, 92 pp. This is a book designed for easy reading on the general subject of dating. This short book covers topics from archeology to tree ring dating to radiocarbon dating of the dead sea scrolls, to dating of meteorites and moon rocks.
The book is out of print, but slightly used copies can be obtained from online dealers like Amazon. Springer-Verlag, New York, pp. This book is a quite comprehensive reference on all methods for determining dates less than about a million years old.
Prometheus Books, Buffalo, pp. This book is a very thorough and comprehensive refutation of young-Earth ideas, written by a non-Christian. The only negative aspect is that at one point Strahler throws in a bit of his own theology--his arguments against the need for a God. This book is long and in small print; it covers a wealth of information. For ice core studies, the Journal of Geophysical Research, volume , starting with page 26,, has 47 papers on two deep ice cores drilled in central Greenland.
Books on scripture, theology, and science: He addresses typical objections brought up by young-Earth adherents, including the death of animals before Adam and Eve's sin, entropy or decay before the fall, the six days of creation, and the flood. This is a very readable theological book about Genesis. Sailhamer has served on the translation committees for two versions of the book of Genesis.
Ross, Hugh Creation and Time: Hugh Ross has a PhD in Astronomy. In this book Dr. Ross defends modern science and an old age for the universe, and refutes common young-Earth arguments. He firmly believes in the inerrancy of the Bible. Schroeder, Paramount, CA, pp. A persuasive book written for the Christian layman. Stoner uses arguments both from the theological and the scientific side.
He talks somewhat philosophically about whether God deceives us with the Genesis account if the Earth is really old. Stoner also tries to discuss the meaning of the Genesis 1 text. Van Till Howard J. This book talks about the misuse of science by both hard-line atheists and by young-Earth creationists. A good deal of the book is devoted to refuting young-Earth arguments, including a substantial section on the Grand Canyon geology.
Its authors are well-known Christians in Geology and Physics. Wiester, John The Genesis Connection. John Wiester has taught Geology at Westmont and Biola University, and is active in the American Scientific Affiliation, an organization of scientists who are Christians.
This book discusses many scientific discoveries relating to the age of the Earth and how these fit into the context of Genesis 1. He argues for an old Earth and refutes many of the common young-Earth claims including their objections to radiometric dating. The following people are sincerely thanked for their contributions to the first edition: Davis Young Calvin College , Dr. I thank my wife Gwen, and children, Carson and Isaac, for supporting me in this work, and I thank God for giving us the intelligence to understand little bits and pieces of His amazing creation.
More about the author: Wiens received a bachelor's degree in Physics from Wheaton College and a PhD from the University of Minnesota, doing research on meteorites and moon rocks. He spent two years at Scripps Institution of Oceanography La Jolla, CA where he studied isotopes of helium, neon, argon, and nitrogen in terrestrial rocks. He worked seven years in the Geological and Planetary Sciences Division at Caltech, where he continued the study of meteorites and worked for NASA on the feasibility of a space mission to return solar wind samples to Earth for study.
Wiens wrote the first edition of this paper while in Pasadena. In he joined the Space and Atmospheric Sciences group at Los Alamos National Laboratory, where he has been in charge of building and flying the payload for the solar-wind mission, as well as developing new instruments for other space missions.
He has published over twenty scientific research papers and has also published articles in Christian magazines. Wiens became a Christian at a young age, and has been a member of Mennonite Brethren, General Conference Baptist, and Conservative Congregational, and Vineyard denominations.
He does not see a conflict between science in its ideal form the study of God's handiwork and the Bible, or between miracles on the one hand, and an old Earth on the other.
Alpha decay Radioactive decay in which the atom's nucleus emits an alpha particle. An alpha particle consists of two neutrons and two protons--the same as a helium atom nucleus.
In alpha decay, the daughter is four atomic mass units lighter than the parent. Alpha decay is most common in heavy elements. Atom The smallest unit that materials can be divided into. An atom is about ten billionths of an inch in diameter and consists of a nucleus of nucleons protons and neutrons surrounded by electrons.
Beta decay Radioactive decay in which the atom's nucleus emits or captures an electron or positron. The daughter ends up with the same mass as the parent, but ends up with one more neutron and one less proton, or vice versa. Because of the different number of protons, the daughter is a different element with different chemical properties than the parent. Bound-state beta decay A special kind of beta decay in which an electron is given off by the nucleus, and the electron ends up in an inner orbital, or electron shell.
This kind of decay only occurs if the nucleus is stripped of the electrons that would normally be in the inner electron shells. As such, this decay only occurs in the center of stars, and was only confirmed experimentally in the s. Calibration The cross-checking of one measurement with another, usually more certain measurement.
Essentially every method of measurement, whether a thermometer, a ruler, or a more complicated instrument, relies on calibration for accuracy. Carbonate A term used rather loosely in this context to describe deposits containing the carbonate anion.
Carbonates play an important role in many caves, where cave formations are the result of dissolution and re-precipitation of material interacting with carbonic acid. Carbonates in recent cave deposits are useful because of their high carbon content, which can be used to calibrate radiocarbon with uranium-series ages. Closed system A system rock, planet, etc. In reality there is always some exchange or influence, but if this amount is completely insignificant for the process under consideration e.
Cosmic ray A very high-energy particle which flies through space. Cosmic Rays are stopped by the Earth's atmosphere, but in the process, they constantly produce carbon, beryllium, chlorine, and a few other radioactive isotopes in small quantities. Cosmic-ray exposure dating Dating of surfaces exposed to cosmic rays by measuring the neon, helium-3, or other cosmogenic isotopes produced in rocks or meteorites exposed to cosmic rays.
Cosmogenic Produced by bombardment of cosmic rays. Carbon is said to be cosmogenic because it is produced by cosmic rays hitting the Earth's atmosphere. Daughter The element or isotope which is produced by radioactive decay. Decay The change from one element or isotope to another. Only certain isotopes decay.
The rest are said to be stable. Dendrochronology The counting of yearly growth rings on trees. To unlock this lesson you must be a Study. Did you know… We have over 95 college courses that prepare you to earn credit by exam that is accepted by over 2, colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.
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Explore over 4, video courses. Find a degree that fits your goals. Learn about half-life and how it is used in different dating methods, such as uranium-lead dating and radiocarbon dating, in this video lesson.
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Create an account to start this course today. Principles of Radiometric Dating. Relative Dating with Fossils: Index Fossils as Indicators of Time. Methods of Geological Dating: Numerical and Relative Dating. What is Relative Dating?
Absolute Time in Geology. What is Carbon Dating? Applications of Nuclear Chemistry. Major Eons, Eras, Periods and Epochs. What is Relative Age? Prentice Hall Earth Science: Remedial High School Physical Science. Holt McDougal Earth Science: Middle School Life Science: Radiometric dating is used to estimate the age of rocks and other objects based on the fixed decay rate of radioactive isotopes.
Radiometric Dating The aging process in human beings is easy to see. Radioactive Decay The methods work because radioactive elements are unstable, and they are always trying to move to a more stable state. Want to learn more?
Select a subject to preview related courses: Half-Life So, what exactly is this thing called a half-life? Uranium-Lead Dating There are different methods of radiometric dating that will vary due to the type of material that is being dated.
Potassium-Argon and Rubidium-Strontium Dating Uranium is not the only isotope that can be used to date rocks; we do see additional methods of radiometric dating based on the decay of different isotopes. Radiocarbon Dating So, we see there are a number of different methods for dating rocks and other non-living things, but what if our sample is organic in nature? Lesson Summary Let's review. Learning Outcomes As a result of watching this video, you might be able to: Compare radiometric dating, radioactive decay and half-life Understand that uranium-lead dating is one of the most reliable radiometric dating methods Relate the processes of potassium-argon and rubidium-strontium dating Determine how radiocarbon dating works and recognize why it is important.
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Imsges: can radioactive dating be used to date sedimentary rocks
Half-Life So, what exactly is this thing called a half-life? Another layering technique uses seasonal variations in sedimentary layers deposited underwater. In he joined the Space and Atmospheric Sciences group at Los Alamos National Laboratory, where he has been in charge of building and flying the payload for the solar-wind mission, as well as developing new instruments for other space missions.
The ratio of 40 K atoms that decay to 40 Ar to those that decay to 40 Ca is 0. See text for explanation.
Bound-state beta decay A special kind of beta decay in which an electron is www.online dating sites off by the nucleus, and the electron ends up in an inner orbital, or electron shell. We have already mentioned dendrochronology tree ring dating above. Also unlike the hourglass, there is no way to change the rate at which radioactive atoms decay in rocks. Carbon is continually being created in the can radioactive dating be used to date sedimentary rocks due to the action of cosmic rays on nitrogen in the air. Alpha decay is most common in heavy elements.
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