Everything About Dating Techniques

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Information about Everything About Dating Techniques

Published on December 8, 2008

Author: litlleboy2



Everything About Dating Techniques : Everything About Dating Techniques Dating Techniques : Dating Techniques Radiometric Dating Radiocarbon Uranium-lead Potassium-argon Rubidium-strontium Samarium-neodymium Rhenium-osmium Lutetium-hafnium Isochron Fission track Thermoluminescence Optically stimulated luminescence Electron spin resonance Dendrochronology Paleo/Archaeo-magnetism Stratigraphic Superposition Molecular Clock Radiocarbon Dating (Riddle, Dating) : Radiocarbon Dating (Riddle, Dating) A radioactive isotope is an unstable form of an element. It will decay to a more stable element. Carbon 14 is unstable and decays to Nitrogen at a known rate. Carbon 14 and carbon 12 (the stable form) are present in the atmosphere and are metabolized into the bodies of all living things in the same ratio as in the atmosphere. At death, carbon 14 levels decrease due to decay, while carbon 12 remains constant. Scientists can measure the ratio of carbon 14 to carbon 12 (a stable form). If the ratio at death is known, then the period of time needed to decay to the present ratio may be calculated. How Carbon-14 Is Produced : How Carbon-14 Is Produced Cosmic Rays (radiation) Collision with atmosphere (N14) Slide 5: Carbon 14 is created in the atmosphere when carbon 12 is bombarded by cosmic rays. Carbon 14 is removed from the atmosphere by decay. It is estimated that it would take 10,000 to 30,000 years for the atmosphere to reach an equilibrium between carbon 12 and carbon 14. Since the earth is theorized to have had life on it for 3.8 billion years, equilibrium must have been reached. Therefore, scientists assume the carbon ratio at death in a dated organism would be the same in the past as it is today. Unfortunately, repeated experiments have found that the rate carbon 14 is added to the atmosphere is 25% faster than the rate at which it is taken away. If there was less carbon 14 in the past, this method provides artificially inflated ages. Besides providing evidence for an Earth age of less than 30,000 years, this fact invalidates the carbon dating as a dating method. Slide 6: There are various factors that affect the carbon ratio: The Earth’s Magnetic Field The earth’s magnetic field reflects cosmic rays back into space, reducing the rate of carbon 14 production. How well it does this is dependent on its strength. As previously mentioned, the magnetic field’s strength has not been constant. In fact it is steadily decreasing. If it was stronger in the past, there would have been less carbon 14 and organisms that died then would give artificially old ages if dated today. More Carbon in the Past Massive coal and oil deposits are buried in the ground. These minerals come from decayed organic matter and are rich in Carbon. This amount of carbon was on the surface of the earth in the past. The carbon 14 would have been much diluted and the carbon ratio smaller. This is happening today as oil is burned for energy, creating carbon dioxide, a major contributor to global warming. (Erkan, 1990) : (Erkan, 1990) The Ice Age Carbon Dioxide becomes trapped in ice While the ice exists the Carbon 14 decays leaving Carbon 12. As the earth became warmer, vast amounts of carbon 12 were released from the receding ice sheets and glaciers, diluting the carbon 14. Volcanically Expelled Carbon Carbon 12 exists deep in the earth. When it is expelled in an eruption, the carbon 14 in the vicinity is diluted. Carbon Dating Summary : Carbon Dating Summary Radiocarbon dating is not an accurate method. Radiocarbon is one of many cosmogenic isotopes that are used for dating. The others are subject to similar limitations. These are: Helium Beryllium Neon Aluminum Chlorine Calcium Iodine There are additional problems with radioactive isotope dating which I will investigate in the next few slides. Uranium Lead Dating (Riddle, Dating) : Uranium Lead Dating (Riddle, Dating) Uranium decays to thorium, which decays to lead, producing helium, which leaches out of the rock at a constant, rapid rate. Scientists date rocks by measuring the uranium and its decay products. Scientists must use several assumptions to arrive at a date: At the time of origin, there was only Uranium, and no daughter elements. The sample was always in a closed environment, so that all the measured daughter elements arose from the uranium decaying in the sample. The decay rate has always been constant. Lack of Agreement Between Dating Methods : Lack of Agreement Between Dating Methods Similar assumptions apply to all the various radiometric dating techniques. If they are sound, then using a variety of techniques on a single sample should provide similar dates. This is not the case. Here are a two examples. The uranium actually creates two products in the decay process—lead and helium. As previously mentioned, dates taken from helium measurements provide much younger ages than from the lead measurements. Volcanic rock from the grand canyon was dated using four methods: uranium-lead, potassium-argon, rubidium-strontium and samarium-neodymium. Dates from 841.5 million years old to 1,379 million years old were obtained. These dates should have all agreed if the radiometric dating assumptions are correct (Snelling, 2007). A Closed System? : A Closed System? The rock to be dated must be in a closed system for the dating process to work. However, it is impossible to know what forces of nature have acted on a rock during its history before it was uncovered and sampled. The Koongarra Formation (Snelling, 1981) A rock formation in Koongarra, Australia was uranium dated using several core samples with very erratic results. The researchers concluded that the rock was contaminated with daughter products at formation, and after formation, both uranium and the daughter products migrated freely over the rock formation. The researchers finally declared that “A logical extension of these data and conclusions is to suggest as others have that U/Pb ratios may have nothing to do with the age of a mineral. So that in spite of the ‘popular’ dating results looking sensible, the evidence clearly indicates that these dates are meaningless.” U and Pb are the elemental symbols of uranium and lead respectively. Decay Rates : Decay Rates The constancy of radioactive decay rates is an assumption induced from a lack of observation to the contrary. However, it is theoretically possible (Snelling, 2007). There is evidence that at some point in the past, decay rates were radically different than they are today. As previously mentioned, helium trapped in rocks showed that uranium had been decaying for 6000 years at a rate that would normally have taken 1.5 billion years to create the measured amount of daughter products. Also previously mentioned, radio halos of polonium214, which has a half life of 164 microseconds, have been found trapped in granite. The decay rate must have been radically different for the polonium to have lasted long enough for the granite to cool, allowing the etching of radio halos. Laboratory experiments have changed the decay rates of elements by changing their chemical environment (Walker, 2000). If it happens in the laboratory, it can happen in nature. One striking example was that of the rhenium-osmium isotopic clock being accelerated by 9 orders of magnitude, and the lutetium-hafnium isotopic clock being accelerated 14 orders of magnitude (Woodmorappe, 2001). Potassium Argon Dating (Riddle, Dating) : Potassium Argon Dating (Riddle, Dating) Potassium argon dating works similar to the other radioisotope dating methods and carries similar assumptions. This method is used to date lava rocks—basalt. When the rock is molten, all the argon escapes out of the rock, leaving only potassium. The potassium becomes closed off in the cooled rock and decays to argon. Scientists calculate the age of a rock from the ratio of potassium to argon in the sample. Potassium Argon Assumptions : Potassium Argon Assumptions Besides other assumptions previously scrutenized, two that are very important to potassium argon dating are: All the original argon escaped before the rock cooled. The cooled rock creates a closed system, so neither potassium or argon migrate in or out of the rock. Slide 15: Scientists do not know all the chemical processes that occur in the rock during its history, that could affect the potassium argon ratio (Wilson, 2005). There are many cases of excess argon being incorporated into cooling lava rocks from the parent magma. In fact, experiments have demonstrated that under certain conditions of pressure and temperature, rocks absorb argon. This excess argon is indistinguishable from the radiogenic argon (Snelling, Potassium). Slide 16: Here are a few examples: (Doolan, 1990) In Aukland, New Zealand, 16 volcanoes were dated. The most recent one, Rangitoto, was believed to have been only a couple hundred years old. Yet Potassium argon dating of 10 samples resulted in dates from 146,000 to 465,000 years old. Wood from beneath the lava flow was then carbon dated at 225 yrs. 10 of the other volcanoes were cross checked with carbon dates, all with drastic differences. Slide 17: (Snelling, 2006) The cardenas basalts at the bottom of the rock layers observed in the Grand Canyon were dated using several different methods, all yielding different results: Potassium-argon isochron 516±30 million years Rubidium-strontium isochron 1,111±81 million years Samarium-neodymium isochron 1,588±170 million years In addition, one author cited over 20 examples of potassium argon dates being drastically older than known dates of origin for various volcanic rock formations (Snelling, Excess). Isochron Dating (Snelling, 1992) : Isochron Dating (Snelling, 1992) Isochron dating is a technique applied to other isotopic clocks to make the calculations more accurate. It was developed in response to the observed inaccuracies of the other methods. In isochron dating, multiple samples are taken from the same rock and dated. The results are plotted on a graph and fitted to a line. The term isochron refers to this line. Problems with Isochron Dating : Problems with Isochron Dating This method carries several assumptions: Decay rates were constant. The rocks were preserved in a closed system. All the samples were from the same rock formation. The daughter isotope was evenly distributed through the rock at the time of formation. Unfortunately, when this method is used, often data points form multiple isochrons, as if parent and daughter isotopes were mixed into the rock, concealing any pattern of decay. Fission Track Dating (Fission-track, CreationWiki) : Fission Track Dating (Fission-track, CreationWiki) When uranium238 decays in a crystal, like volcanic glass, the emitted alpha particles etch paths in the crystal lattice along their trajectories. The number of fission tracks is related to the length of time the uranium has been decaying. This method assumes the constancy of decay rates, as well as the accuracy of a human counter. Unfortunately, the tracks can sometimes be hard to differentiate from each other, cracks in the lattice, and tracks from other decaying isotopes. Slide 21: Fission tracks from uranium238 Luminescence and Electron Spin Resonance (ESR) (Michaels, 2003) : Luminescence and Electron Spin Resonance (ESR) (Michaels, 2003) In crystalline rocks and ceramics, radioactively decaying materials release electrons, some of which become trapped in imperfections in the crystal lattice. In Thermoluminescence, heating the rock to over 350° Celsius releases the trapped energy in a flash of light. The intensity of the light is proportional to the amount of trapped energy, which is proportional to the time that it has been accumulating since the last heating or exposure to sunlight. Slide 23: In Optically Stimulated Luminescence, laser beams are used to release the energy. In ESR, microwaves and variable magnetic fields are used to measure the latent radiation energy, so measurements of the same sample can be repeated, unlike in the other two methods. It is less reliable than the other two models because it is more complicated (Thompson, Luminescence). Slide 24: When calculating a date, scientists must establish the rate at which the electrons have been accumulating. They do this by measuring the reactivity of the surrounding soil (the rate at which the electrons are emitted). Problems with Luminescence and ESR : Problems with Luminescence and ESR (Walker, 2003) This method has 4 major assumptions: The radiation clock was reset before deposition. The change in radiation content is solely the result of the radiation in the environment. The amount of radiation in the environment has remained constant. The ability of the crystal to trap the radiation has remained constant. Slide 26: If a rock was heated, or briefly uncovered and exposed to sunlight after coming to rest in it’s final location, the date would not be reliable. Temperature and chemical changes in the soil, as would have been the case during the ice age could have changed the lattice structure’s ability to trap electrons. Previously discussed migration of radioactive elements in the soil or a change in decay rates would alter the surrounding radioactivity. Summary of Radiometric Dating Methods : Summary of Radiometric Dating Methods The ratios of parent to daughter isotopes, or levels of trapped radiation in rocks is the result of many processes that are not understood. The previous example of the cardenas basalts at the bottom of the grand canyon yielded a Rubidium-strontium isochron date of 1,111±81 million years. Yet another basalt flow in the same area, one that had erupted more recently on top of the canyon rim and cascaded down the side over all the preceding layers, was dated by the same method and gave a date of 1,143±220 million years. In this case at least, it appears that the ratio had nothing to do with age, but more with the region from which the magma flowed (Snelling, 2006). Paleomagnetic/Archaeomagnetic Dating (Michaels, 2003) : Paleomagnetic/Archaeomagnetic Dating (Michaels, 2003) The earth’s magnetic poles change direction constantly and independent of each other. When a rock is molten, iron particles align their dipoles with earth’s magnetic field at that location. When the rock solidifies, the iron particles keep their magnetic alignment, thus preserving a record of the earths magnetic field orientation at the time. Slide 29: Scientists have assigned dates to magnetized samples all over the world using other dating methods, like radiometric dating. Thus a master map of the magnetic field’s wanderings through time has been constructed. Now, when scientists find a magnetized sample, they correlate it with the master map to find when it could have originated. Problems with Magnetic Dating : Problems with Magnetic Dating Certain chemical processes in the rocks can realign the magnetism long after the rocks have been formed. Rocks can be moved by the whether, burrowing animals, man, seismic forces, and continental drift. As already discussed, the dating methods used to arrive at the master map are not accurate. Slide 31: The general direction of the magnetic field is only apparent above the surface of the earth. The magnetized rock formations on the surface create many anomalies in the direction of the magnetic field in the local area, as anyone who has navigated by compass can testify. A rock would therefore align with the local magnetic field direction created by previously magnetized formations, and not the actual geomagnetic pole. Summary of Magnetic Dating : Summary of Magnetic Dating Paleomagnetic dating incorporates so many uncertainties that it is impossible to arrive at an accurate date using this method. Dendrochronology (Batten, 2001) : Dendrochronology (Batten, 2001) Dendrochronology is the use of tree rings to measure time. A tree makes a new ring of growth every year. The more nutrients the tree obtains in a given year, the thicker the ring, creating a pattern of thicker and thinner rings in a cross section of wood. Slide 34: The steps of dating a piece of wood using dendrochronology are as follows: A piece of wood is carbon dated. Then the rings on a cross section of a recently living tree are counted back to the carbon 14 date. Then a ring growth pattern on the sample is calibrated with a pattern on the younger tree to get a more exact date and to extend the chronology back even further. Other samples may be calibrated to the sample with the confirmed date. Problems with Dendrochronology : Problems with Dendrochronology Carbon 14 dating is a poor dating method, as previously discussed. Trees have been observed to make up to 5 rings in a single year. It is impossible to match tree ring patterns between trees. Trees growing next to each other don’t even have the same pattern. Often, the best matching pattern is rejected in favor of preserving the Carbon 14 date. Stratigraphic Superposition (Stratigraphy, Wikipedia) : Stratigraphic Superposition (Stratigraphy, Wikipedia) If an object is left undisturbed on the surface of the earth, matter will accumulate on it, eventually burying it. The deeper an object is in the ground, the longer it has been buried. Curiously, in many places, the earth is layered into strata, the geologic column. It is theorized that each layer represents a different epoch in earths history, with deeper layers being older. Slide 37: If an object of known date is found in a layer, it is assumed that the surrounding layer is the same age as the object. Objects nearby in the same layer are assumed to be the same age as the original object. Problems with Stratigraphic Superposition : Problems with Stratigraphic Superposition It is quite reasonable that an object buried deep in the earth is probably older than a similar one on the surface, such as the case with cities being built on top of previous ones, like Pompeii. The problems arise from the assumption that the layers represent a time line. Slide 39: The dates assigned to layers are the result of radiometric dating, which as previously discussed, doesn’t work. Due to the relatively short life spans of human civilizations, it would be impossible to observe strata being formed over billions of years. Therefore, the claim that billions of years is responsible for strata cannot be disproven. Therefore, it is not true science. On the contrary, the claim that rock strata are created rapidly by catastrophic events can and has been observed. Slide 40: When Mount Saint Helens erupted on May 18, 1980, layers of strata piled up to 400 ft high were deposited in days (Mount St. Helens, CreationWiki). Laboratory experiments have demonstrated the formation of strata from sediments in agitated water. Besides showing that lower strata is not newer strata, the experiments also show that a single strata is not the same age at different points (Berthault, 1997). Polystrate fossills show that strata was deposited rapidly (Polystrate, Wikipedia). Slide 41: When a fossil is not contained in strata above a certain point, it is assumed that this is the result of one of the previously mentioned mass extinctions. Scientists use these fossils as indexes, meaning that layers containing them are dated as from before the time of the mass extinction. Slide 42: (Riddle, Dating) Fossil species found here Not found above=extinct Not found below=not yet evolved Coelacanth : Coelacanth One example is the coelacanth. This creature was supposed to have suffered the same fate as the dinosaurs until it was discovered alive. Therefore, the absence of fossils in higher layers is due to other processes (Brown, 2008). As previously mentioned, fossils have also been found in layers lower than they should have according to the generally accepted view. Therefore the layers are meaningless. They are not a progression of life forms, nor do they represent millions of years. Molecular Clock (Molecular, Wikipedia) : Molecular Clock (Molecular, Wikipedia) Evolutionists theorize that the rate at which genes mutate is constant. If they know the rate, they can then calculate how long ago the species differentiated from a common ancestor. Evolutionists calibrate the clock using evolutionary trees and the fossil record. This is the reasoning behind “Mitochondrial Eve.” Slide 45: Mitochondrial dating of a common human ancestor does have some merit, as it does not depend on evolutionary assumptions about speciation. However, they still calibrate the clock using the theoretical time scale of evolution. The assigned date for Mitochondrial Eve is 140,000 years ago (Mitochondrial, Wikipedia). Modern studies of the actual rate of mitochondrial mutation have shown that it is about 1 in 40 generations, not 1 in 600 generations as was supposed. This puts Mitochondrial Eve at about 6500 years ago (Wieland, 1998) Summary of Dating Methods : Summary of Dating Methods The dating methods currently used are fraught with assumptions that don’t fit with observations. When Edison built a light bulb that didn’t work, he accepted the fact that his assumptions did not fit his observations and he went back to the drawing board. He did not claim that it worked even when everyone could see that it didn’t. This is actually what is being done now in regard to dating methods. Slide 47: With the many dating techniques available, and consequently the many dates, how do scientists pick one? In one example, a researcher dated diamonds at 6 billion years old. This date was disregarded because the earth is only supposed to be 4.5 billion years old. The reporting investigator observed that “dates are readily discarded if they do not fit the preconceived notions of the experimenter.” He further reported that the sum response of a group of scientists to whom he presented his concern, was the smug challenge, “Do you have a better method (Williams, 1995)?” Slide 48: (Riddle, Dating)

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