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You may have to talk to your Canvas Administrator at your institution to help you enable and use Quizzes. Atmospheric argon absorbed in this way can be corrected for, because it has a certain amount of argon 36 which can be measured. However, argon also comes up from the interior of the earth, and this argon has very little argon 36 in it, and cannot be detected.
So we can explain the old K-Ar dates just by the fact that rocks absorb so much argon that comes up from the interior of the earth. Older rocks would have more time to absorb argon, and there was probably more argon coming through the earth at the time of the Flood and shortly thereafter than there is today.
In fact, a number of geologists themselves now say that K-Ar dating is not very reliable, or mainly of historical importance. This is quite an admission, since most of the geological time scale is based on K-Ar dating. Another problem with K-Ar dating is that many volcanoes that we know erupted in the past several hundred years give K-Ar dates in the hundreds of thousands or millions of years. A large number of K-Ar dates on which the geological time scale is based, are dates from a mineral called glaucony.
However, many geologists say that this mineral is highly unreliable for dating.
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So here we have a large part of the geological time scale based on a mineral which geologists themselves say is highly unreliable. So I guess we'll have to discard K-Ar dating as a reliable dating method.
Now let's consider another method that some textbooks say is reliable. This is the dating of zircons by uranium-lead U-Pb dating and some other related methods. Zircon is a gemstone, a mineral that can have a considerable amount of uranium in it. However, when zircons form, they exclude lead. Over time, uranium decays to lead.
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By measuring the amount of uranium and lead in a zircon and knowing the rate of decay, we can measure the age of the zircon. Lead is somewhat mobile, however, as is uranium, and so other methods have been devised that can date zircons even if some lead leaves the rock. The problem with this method is that zircons can include lead when they form, throwing off the date.
They can also lose uranium. In addition, they can travel through lava without melting, so the date computed for a zircon may be measuring a much older event than the lava flow itself. Even geologists recognize that ages given by zircons are often much too old, even for them.
Furthermore, a batch of zircons from the same place will often yield widely different ages. So I guess we'll have to discard zircons as a reliable dating method. The next candidate dating method is fission track dating.
Some minerals contain uranium which decays by fission. It splits in two, and the pieces fly apart through the mineral, creating fission tracks. These tracks can be made visible by etching with an acid solution, and then counted. By knowing how much uranium there is in a rock and by counting the number of fission tracks, one can measure the age of the rock.
There are a number of problems with this method, and even geologists have had intense disagreements about its reliability. The ages often do not agree with what geologists expect. One problem is that certain constants involved in this method are not known or are hard to estimate, so they are calibrated based on the "known" ages of other rocks. If these other "known" ages are in error, then fission track dates are in error by the same amount. Another problem is that fission tracks fade at high temperatures. So if there are too few tracks, the geologist can always say that most of them faded away.
To get a fission track date, one has to know something about the temperature history of a rock.
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Another problem is that uranium can be removed from a rock by water. If a sample loses 99 percent of its uranium, then the fission track date will be times too old. Another problem is knowing what is a fission track and what is just an imperfection in the rock.
Geologists themselves suggest that imperfections are at times mistaken for fission tracks, and admit that fission tracks are not always easy to recognize. Textbooks have beautiful, clean pictures of fission tracks, but I doubt that these illustrations correspond to reality.
Along this line, it is interesting to note that for every fission of uranium , there are over a million decays by a process called alpha decay, in which a helium nucleus is ejected from the nucleus of uranium. The alpha particle creates a long, thin trail of damage, and the former uranium nucleus recoils in the other direction, creating a short, wide track about one thousandth as long as a fission track. Not only this, but what's left of the uranium nucleus having lost the helium nucleus decays by thirteen more steps until it becomes lead, so there are over fourteen million other decays for every fission track.
Over four million of these occur within a few days. All of these decays emit particles that damage the crystal structure. Some of these decays emit alpha particles, and some emit beta particles, which are energetic electrons. In addition, many millions of gamma rays are emitted, which are high-energy electromagnetic radiation like X rays, and also damage the crystal structure.
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Perhaps the damage created by all this radiation can be increased by chemical action and be etched by acid to appear like fission tracks. Or if two alpha particle trails are close enough together, perhaps they can damage the crystal enough so that their combined trail will be etched away by acid like a fission track.
Minerals are also subject to alteration by water, which may contain chemicals that react with the rock. Over long periods of time, all of these processes can damage the crystal structure, and it may be that when the mineral is etched with acid, track-like formations appear as a result.