Radiometric dating - Wikipedia

Chronological dating

what dating method is used for fossils

Also, samples taken a few feet apart can give ages that differ by many hundreds of millions of years. The mass spectrometer was invented in the s and began to be used in radiometric dating in the s. The reason this age may not be a true age—even though it is commonly called an absolute age—is that it is based on several crucial assumptions. There are many other methods that can be used to establish ages for parts of the earth and the solar system. These rocks were dated at up to 3.

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However, local eruptions of volcanoes or other events that give off large amounts of carbon dioxide can reduce local concentrations of carbon and give inaccurate dates. This scheme has application over a wide range of geologic dates. These findings point to the age of the earth being much younger than evolutionary scientists would suggest. Dating methods based on extinct radionuclides can also be calibrated with the U-Pb method to give absolute ages. Pottery shards can be dated to the last time they experienced significant heat, generally when they were fired in a kiln. The scheme has a range of several hundred thousand years. The assumption that there has been no loss or gain of the isotopes in the rock assumption 2 does not take into account the impact of weathering by surface and ground waters and the diffusion of gases.

There are three main assumptions that must be made to accept radiometric dating methods. These must be accepted on faith in uniformitarian and naturalistic frameworks.

Recent research by a team of creation scientists known as the RATE R adioisotopes and the A ge of T he E arth group has demonstrated the unreliability of radiometric dating techniques. Even the use of isochron dating, which is supposed to eliminate some initial condition assumptions, produces dates that are not reliable.

Despite the fact that there are many scientific problems with radiometric dating, there is a more significant problem.

A fear of God and reverence for His Word is the beginning of wisdom. Starting with the Bible and developing a model for dating events in earth history will lead us to the truth. The Bible gives us a much more reliable history of the earth as it was recorded by God.

When someone mentions scientific dating methods, the first thing to come to mind for most people is carbon dating. However, there are many methods that can be used to determine the age of the earth or other objects. The textbooks focus on relative dating, based on the layering of the rocks, and radiometric dating. Relative ages are assigned to rocks based on the idea that rock layers lower in the strata were deposited before rock layers that are higher.

There is also a difference in the timescale used to explain the layers. Determining the relative age of a rock layer is based on the assumption that you know the ages of the rocks surrounding it. Uniformitarian geologists use so-called absolute dating methods to determine the ages of the surrounding rocks.

Certain types of rocks, especially those that form from magma igneous , contain radioactive isotopes of different elements. It is possible to measure the ratio of the different radioactive parent isotopes and their daughter isotopes in a rock, but the ratios are not dates or ages.

The dates must be inferred based on assumptions about the ratios. Carbon dating is another common technique, but it can only be used on carbon-containing things that were once alive. The method of calculating radiometric dates is like using an hourglass. You can use the hourglass to tell time if you know several things: If any of these three conditions is not accurately known, the hourglass will give an inaccurate measure of time. Using an hourglass to tell time is much like using radiometric dating to tell the age of rocks.

There are key assumptions that we must accept in order for the method to be reliable. Radiometric dating is based on the fact that radioactive isotopes decay to form isotopes of different elements. The starting isotope is called the parent and the end-product is called the daughter. The time it takes for one half of the parent atoms to decay to the daughter atoms is called the half-life.

If certain things are known, it is possible to calculate the amount of time since the parent isotope began to decay. For example, if you began with 1 gram of carbon, after 5, years you would be left with 0. The reason this age may not be a true age—even though it is commonly called an absolute age—is that it is based on several crucial assumptions.

Most radiometric dating techniques must make three assumptions:. The major problem with the first assumption is that there is no way to prove that the decay rate was not different at some point in the past.

It is true that radioisotope decay rates are stable today and are not largely affected by external conditions like change in temperature and pressure, but that does not mean that the rate has always been constant. Recent research by a creation science group known as RATE R adioisotopes and the A ge of T he E arth has produced evidence of accelerated rates of decay at some point or points in the past.

Creation scientists suggest that there are two possible times that God supernaturally intervened on a global scale—during Creation Week and the Flood. It is not unreasonable to assume that God used the energy of accelerated radioactive decay to initiate and drive the major geologic changes in the earth that accompanied the Flood.

Evidence for the period of accelerated decay is found in zircon crystals. Zircon crystals in granite contain radioactive uranium, which decays into lead over time. As the uranium decays, helium is produced in the crystals. Helium escapes from the crystals at a known, measurable rate. If those rocks were over a billion years old, as evolutionists claim, the helium should have leaked out of the rock.

The presence of lots of helium in the crystals is evidence in support of a young earth. Fossils and rocks do not come with dates stamped on them.

The dates must be interpreted based on the evidence. Biblical geologists start with the assumptions laid out in the Bible and conclude that the rocks must be less than 6, years old. Evolutionists reject the authority of the Bible and conclude that the rocks must be millions or billions of years old. Other important findings of the RATE project include detecting carbon in coal and diamonds. If these substances were really millions or billions of years old respectively, there should be no carbon left in them.

Carbon has a half-life of 5, years. With the most accurate mass spectrometers, the oldest calculated age of items containing carbon is about 80, years. Diamonds are assumed to be many billions of years old and should contain no detectable carbon as it would have all decayed to nitrogen long ago.

The same is true of coal which was supposedly deposited hundreds of millions of years ago, according to the evolutionary model. The presence of carbon in these materials clearly supports the idea of a young earth as described by the Bible. The assumption that there has been no loss or gain of the isotopes in the rock assumption 2 does not take into account the impact of weathering by surface and ground waters and the diffusion of gases.

It is impossible to know to what degree the parent and daughter products have been added to or removed from the rocks over the alleged millions or billions of years. Also, samples taken a few feet apart can give ages that differ by many hundreds of millions of years. Many people do not realize that fossils themselves are usually not directly dated. Early geologists, in the s and s, noticed how fossils seemed to occur in sequences: The first work was done in England and France.

Then, geologists began to build up the stratigraphic column, the familiar listing of divisions of geological time — Jurassic, Cretaceous, Tertiary, and so on. Each time unit was characterized by particular fossils. The scheme worked all round the world, without fail. From the s onwards, geologists noted how fossils became more complex through time.

The oldest rocks contained no fossils, then came simple sea creatures, then more complex ones like fishes, then came life on land, then reptiles, then mammals, and finally humans. Since , paleontologists, or fossil experts, have searched the world for fossils. In the past years they have not found any fossils that Darwin would not have expected.

Darwin and his contemporaries could never have imagined the improvements in resolution of stratigraphy that have come since , nor guessed what fossils were to be found in the southern continents, nor predicted the huge increase in the number of amateur and professional paleontologists worldwide. All these labors have not led to a single unexpected finding such as a human fossil from the time of the dinosaurs, or a Jurassic dinosaur in the same rocks as Silurian trilobites.

Paleontologists now apply sophisticated mathematical techniques to assess the relative quality of particular fossil successions, as well as the entire fossil record.

These demonstrate that, of course, we do not know everything and clearly never will , but we know enough. Today, innovative techniques provide further confirmation and understanding of the history of life. Biologists actually have at their disposal several independent ways of looking at the history of life - not only from the order of fossils in the rocks, but also through phylogenetic trees.

Phylogenetic trees are the family trees of particular groups of plants or animals, showing how all the species relate to each other. Phylogenetic trees are drawn up mathematically, using lists of morphological external form or molecular gene sequence characters. Modern phylogenetic trees have no input from stratigraphy, so they can be used in a broad way to make comparisons between tree shape and stratigraphy.

The majority of test cases show good agreement, so the fossil record tells the same story as the molecules enclosed in living organisms. Dating in geology may be relative or absolute. Relative dating is done by observing fossils, as described above, and recording which fossil is younger, which is older. The discovery of means for absolute dating in the early s was a huge advance. The methods are all based on radioactive decay:.

One of its great advantages is that any sample provides two clocks, one based on uranium's decay to lead with a half-life of about million years, and one based on uranium's decay to lead with a half-life of about 4. This can be seen in the concordia diagram, where the samples plot along an errorchron straight line which intersects the concordia curve at the age of the sample.

This involves the alpha decay of Sm to Nd with a half-life of 1. Accuracy levels of within twenty million years in ages of two-and-a-half billion years are achievable. This involves electron capture or positron decay of potassium to argon Potassium has a half-life of 1. This is based on the beta decay of rubidium to strontium , with a half-life of 50 billion years.

This scheme is used to date old igneous and metamorphic rocks , and has also been used to date lunar samples. Closure temperatures are so high that they are not a concern. Rubidium-strontium dating is not as precise as the uranium-lead method, with errors of 30 to 50 million years for a 3-billion-year-old sample.

A relatively short-range dating technique is based on the decay of uranium into thorium, a substance with a half-life of about 80, years. It is accompanied by a sister process, in which uranium decays into protactinium, which has a half-life of 32, years. While uranium is water-soluble, thorium and protactinium are not, and so they are selectively precipitated into ocean-floor sediments , from which their ratios are measured.

The scheme has a range of several hundred thousand years. A related method is ionium—thorium dating , which measures the ratio of ionium thorium to thorium in ocean sediment. Radiocarbon dating is also simply called Carbon dating. Carbon is a radioactive isotope of carbon, with a half-life of 5, years, [25] [26] which is very short compared with the above isotopes and decays into nitrogen.

Carbon, though, is continuously created through collisions of neutrons generated by cosmic rays with nitrogen in the upper atmosphere and thus remains at a near-constant level on Earth.

The carbon ends up as a trace component in atmospheric carbon dioxide CO 2. A carbon-based life form acquires carbon during its lifetime. Plants acquire it through photosynthesis , and animals acquire it from consumption of plants and other animals.

When an organism dies, it ceases to take in new carbon, and the existing isotope decays with a characteristic half-life years. The proportion of carbon left when the remains of the organism are examined provides an indication of the time elapsed since its death. This makes carbon an ideal dating method to date the age of bones or the remains of an organism.

The carbon dating limit lies around 58, to 62, years. The rate of creation of carbon appears to be roughly constant, as cross-checks of carbon dating with other dating methods show it gives consistent results.

However, local eruptions of volcanoes or other events that give off large amounts of carbon dioxide can reduce local concentrations of carbon and give inaccurate dates. The releases of carbon dioxide into the biosphere as a consequence of industrialization have also depressed the proportion of carbon by a few percent; conversely, the amount of carbon was increased by above-ground nuclear bomb tests that were conducted into the early s. Also, an increase in the solar wind or the Earth's magnetic field above the current value would depress the amount of carbon created in the atmosphere.

This involves inspection of a polished slice of a material to determine the density of "track" markings left in it by the spontaneous fission of uranium impurities. The uranium content of the sample has to be known, but that can be determined by placing a plastic film over the polished slice of the material, and bombarding it with slow neutrons.

This causes induced fission of U, as opposed to the spontaneous fission of U. The fission tracks produced by this process are recorded in the plastic film. The uranium content of the material can then be calculated from the number of tracks and the neutron flux. This scheme has application over a wide range of geologic dates. For dates up to a few million years micas , tektites glass fragments from volcanic eruptions , and meteorites are best used.

Older materials can be dated using zircon , apatite , titanite , epidote and garnet which have a variable amount of uranium content. The technique has potential applications for detailing the thermal history of a deposit. The residence time of 36 Cl in the atmosphere is about 1 week. Thus, as an event marker of s water in soil and ground water, 36 Cl is also useful for dating waters less than 50 years before the present.

Luminescence dating methods are not radiometric dating methods in that they do not rely on abundances of isotopes to calculate age. Instead, they are a consequence of background radiation on certain minerals.

Over time, ionizing radiation is absorbed by mineral grains in sediments and archaeological materials such as quartz and potassium feldspar. The radiation causes charge to remain within the grains in structurally unstable "electron traps". Exposure to sunlight or heat releases these charges, effectively "bleaching" the sample and resetting the clock to zero.

The trapped charge accumulates over time at a rate determined by the amount of background radiation at the location where the sample was buried. Stimulating these mineral grains using either light optically stimulated luminescence or infrared stimulated luminescence dating or heat thermoluminescence dating causes a luminescence signal to be emitted as the stored unstable electron energy is released, the intensity of which varies depending on the amount of radiation absorbed during burial and specific properties of the mineral.

These methods can be used to date the age of a sediment layer, as layers deposited on top would prevent the grains from being "bleached" and reset by sunlight. Pottery shards can be dated to the last time they experienced significant heat, generally when they were fired in a kiln. Absolute radiometric dating requires a measurable fraction of parent nucleus to remain in the sample rock. For rocks dating back to the beginning of the solar system, this requires extremely long-lived parent isotopes, making measurement of such rocks' exact ages imprecise.

To be able to distinguish the relative ages of rocks from such old material, and to get a better time resolution than that available from long-lived isotopes, short-lived isotopes that are no longer present in the rock can be used.

At the beginning of the solar system, there were several relatively short-lived radionuclides like 26 Al, 60 Fe, 53 Mn, and I present within the solar nebula. These radionuclides—possibly produced by the explosion of a supernova—are extinct today, but their decay products can be detected in very old material, such as that which constitutes meteorites. By measuring the decay products of extinct radionuclides with a mass spectrometer and using isochronplots, it is possible to determine relative ages of different events in the early history of the solar system.

Iamges: what dating method is used for fossils

what dating method is used for fossils

All these labors have not led to a single unexpected finding such as a human fossil from the time of the dinosaurs, or a Jurassic dinosaur in the same rocks as Silurian trilobites.

what dating method is used for fossils

Relative dating methods are unable to determine the absolute age of an object or event, but can determine the impossibility of a particular event happening before or after another event of which the absolute date is well known.

what dating method is used for fossils

If the fossils, or the dating of the fossils, could be shown to be inaccurate, all such information would have to be rejected as unsafe. As an example Pinnacle What dating method is used for fossils 's caves, in the southern coast of South Africaprovided evidence that marine resources speed dating host salary have been regularly fof by humans as ofyears ago. Understanding what those usfd are is important. Currently, he is studying certain basal dinosaurs from the Late Triassic and the quality of what dating method is used for fossils segments of the fossil record. The radiation causes charge to remain within the grains in structurally unstable "electron traps". For all other nuclides, the proportion of the original nuclide to its decay products changes in a predictable way as the original nuclide decays over time. Since then, geologists have made many tens of thousands of usrd age determinations, and they have refined the earlier estimates.