Age Earth is 4.54 Â ± 0.05 billion years (4.54 ÃÆ'â € "10 9 year Ã, Â ± 1%). This age can represent the age of earth's growth, the formation of the nucleus, or the material from which the Earth is formed. The calendar is based on evidence of the radiometric age dating of meteorite materials and is consistent with the radiometric age of the oldest known samples of terrestrial and moon.
Following the development of radiometric age dating at the beginning of the 20th century, measurements of lead in uranium-rich minerals show that some are over a billion years old. The oldest minerals analyzed to date - zircon crystals from Jack Hills in Western Australia - are at least 4.404 billion years old. The richest calcium-aluminum-rich inclusion - the oldest known solid constituent in meteorites formed in the Solar System - is 4.567 billion years old, providing a lower limit for the solar system's age.
It is hypothesized that Earth's growth begins soon after the formation of rich calcium-aluminum-inclusions and meteorites. Since the exact amount of time this accretion process is not known, and the predictions of different accretion models range from several million to about 100 million years, the exact age of the Earth is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed on the surface, since it is a mineral aggregate of various ages.
Video Age of the Earth
Development of modern geological concepts
The study of strata, the coating of rocks and the earth, gave the naturalist an appreciation that the Earth may have gone through many changes during its existence. These layers often contain fossil remains of unknown creatures, causing some to interpret the development of organisms from layer to layer.
Nicolas Steno in the 17th century was one of the first naturalists to appreciate the connection between fossilized remains and strata. His observations led him to formulate important stratigraphic concepts (ie, "superposition laws" and "principles of original horizontality"). In the 1790s, William Smith hypothesized that if two layers of rock in very different locations contain the same fossils, then it makes sense that they have the same age. Nephew and William Smith's student, John Phillips, then calculated that way the Earth is about 96 million years old.
In the mid-18th century, naturalist Mikhail Lomonosov stated that the Earth had been created separately from, and several hundred thousand years before, the rest of the universe. Lomonosov's ideas are mostly speculative. In 1779 Comte du Buffon tried to gain value for the ages of Earth using experiments: He created a small globe that resembled Earth's composition and then measured its cooling rate. This makes him estimate that the Earth is about 75,000 years old.
Other naturalists use this hypothesis to build Earth history, though their timelines are not exact because they do not know how long it takes to lay the stratigraphic layers. In 1830, geologist Charles Lyell developed the ideas found in James Hutton's works, popularizing the concept that Earth's features are constantly changing, eroding and reforming constantly, and the rate of change is approximately constant. This is a challenge to the traditional view, which sees the Earth's history as static, with changes caused by intermittent disasters. Many naturalists are influenced by Lyell to be "uniformitarians" who believe that change is constant and uniform.
Maps Age of the Earth
Initial calculation
In 1862, physicist William Thomson, 1st Baron Kelvin published calculations that improved the Earth's age between 20 million and 400 million years. He assumes that the Earth has formed as a completely liquid object, and determines the amount of time it takes for the near surface to cool to the current temperature. Its calculations do not take into account the heat generated through radioactive decay (a process that was later unknown to science) or, more significantly, convection in the Earth, allowing more heat to escape from the interior to warm rocks near the surface. More constraints are Kelvin's estimate of the age of the Sun, which is based on his estimated heat output and the theory that the Sun derives its energy from gravitational collapse; Kelvin estimates that the Sun is about 20 million years old.
Geologists such as Charles Lyell find it difficult to accept such a short age for Earth. For biologists, even 100 million years seems too short to be plausible. In Darwin's theory of evolution, the process of variation inherited randomly with cumulative selection requires a very long period of time. (According to modern biology, the total evolutionary history from the beginning of life to the present day has taken place from 3.5 to 3.8 billion years ago, the amount of time that has passed since the last ancestors of all living organisms as indicated by geological dating.)
In a lecture in 1869, Darwin's great advocate, Thomas H. Huxley, attacked Thomson's calculations, showing that they seemed right in themselves but based on false assumptions. Physicist Hermann von Helmholtz (in 1856) and astronomer Simon Newcomb (in 1892) contributed their respective calculations of 22 and 18 million years to the debate: they independently calculated the amount of time required for the Sun to condense to its present diameter and brightness of the nebula gas and dust from which it was born. Their values ​​are consistent with Thomson's calculations. However, they assume that the Sun only shines from the heat of its gravitational contraction. The process of solar nuclear fusion has not been known to science.
In 1895, John Perry challenged Kelvin's figure based on his assumptions about conductivity, and Oliver Heaviside entered the dialogue, regarding it as "a vehicle to showcase its operator's method of ability to solve complexity problems."
Other scientists support Thomson's number. Charles Darwin's son, the astronomer George H. Darwin, proposed that the Earth and the Moon burst in the early days when they both melted. He calculates the amount of time that will be taken for tidal frictions to give the Earth 24 hours a day today. Its value of 56 million years adds additional evidence that Thomson is on the right track.
The last forecast Thomson gave, in 1897, was: "that it is over 20 and less than 40 million years old, and probably much closer to 20 than 40". In 1899 and 1900, John Joly calculated the rate at which oceans should accumulate salt from the erosion process, and determined that the oceans were between 80 and 100 million years old.
Radiometric dating
Overview
By their chemical properties, rock minerals contain certain elements and not others; but in rocks containing radioactive isotopes, the process of radioactive decay produces exotic elements over time. By measuring the steady end product concentration of the decay, coupled with the knowledge of half life and the initial concentration of decaying elements, the stone age can be calculated. A typical radioactive end product is argon from a potassium-40 decay, and leads from uranium and thorium decay. If the rock becomes liquid, as occurs in Earth's mantle, such non-radioactive end products usually pass or redistribute. Thus the oldest terrestrial rock age provides a minimum for the Earth's age, assuming that no rock is intact for longer than Earth itself.
Convective and radioactivity coat
In 1892, Thomson had made Lord Kelvin in recognition of his many scientific achievements. Kelvin calculates the age of Earth by using a thermal gradient, and he arrives at an approximate 100 million years. He did not realize that Earth's mantle was convincing, and this denied his estimates. In 1895, John Perry produced an approximate age of Earth of 2 to 3 billion years using convective mantle model and thin crust. Kelvin is stuck with an estimated 100 million years, and then reduced to about 20 million years.
The discovery of radioactivity introduced another factor in calculation. After the early discovery of Henri Becquerel in 1896, Marie and Pierre Curie discovered the radioactive elements of polonium and radium in 1898; and in 1903, Pierre Curie and Albert Laborde announced that radium generated enough heat to melt its own weight in ice in less than an hour. Geologists quickly realized that this disrupted the assumptions that underlie most of Earth's age calculations. This assumes that the original heat of Earth and the Sun has disappeared by itself into space, but radioactive decay means that this heat is constantly replenished. George Darwin and John Joly were the first to show this, in 1903.
Discovery of radiometric dating
Radioactivity, which has overthrowned the old calculations, generates bonuses by providing a basis for new calculations, in the form of radiometric dating.
Ernest Rutherford and Frederick Soddy together continued their work on radioactive material and concluded that radioactivity was due to the spontaneous transmutation of the atomic element. In radioactive decay, elements decompose into other lighter elements, releasing alpha, beta, or gamma radiation in the process. They also determined that certain isotopes of radioactive elements decayed into other elements at different levels. This figure is given in the form of a "beak", or the amount of time it takes half of the mass of the radioactive material to decompose into a "decay product".
Some radioactive materials have a short half-life; some have a long part time. Uranium and thorium have a long half-life, and so survive in the Earth's crust, but the radioactive element with a short half-life generally disappears. It suggests that it is possible to measure the age of the Earth by determining the relative proportions of radioactive materials in geological samples. In fact, the radioactive elements do not always rot into nonradioactive ("stable") elements directly, on the contrary, decay into other radioactive elements that have their own half-life and so on, until they reach the stable element. Such "decay series", such as the uranium-radium and thorium series, are known in years of radioactivity discovery and provide a basis for building radiometric dating techniques.
The pioneers of radioactivity are the energetic Bertram B. Boltwood and Rutherford chemists. Boltwood has been conducting radioactive material research as a consultant, and when Rutherford taught at Yale in 1904, Boltwood was inspired to illustrate the relationship between the elements in various series of decays. In late 1904, Rutherford took the first step toward radiometric dating by suggesting that alpha particles released by radioactive decay could be trapped in rocky materials such as helium atoms. At the time, Rutherford only guessed the connection between alpha particles and helium atoms, but he would prove his connection four years later.
Soddy and Sir William Ramsay have just determined the rate at which radium produces alpha particles, and Rutherford suggests that he can determine the age of rock samples by measuring the concentration of helium. He dated the stone in his for 40 million years old with this technique. Rutherford writes,
I went into the room, which was half dark, and at this moment saw Lord Kelvin amongst the audience and realized that I was in trouble in the last part of my speech dealing with the age of the Earth, where my views contradicted him. To my relief, Kelvin fell into a deep sleep, but when I got to the point, I saw the old bird sitting up, opening my eyes, and tilting a bad look at me! Then suddenly came the inspiration, and I said, "Lord Kelvin has limited the age of the Earth, as long as no new source is found." The prophetic statement refers to what we now consider tonight, radium! " Look! The old boy beamed at me.
Rutherford assumes that the radium decay rate as determined by Ramsay and Soddy is accurate, and that helium does not escape from the sample over time. Rutherford's scheme is not accurate, but it is a useful first step.
Boltwood focuses on the final product of the decay series. In 1905, he suggested that lead is the final stable product of radium decay. It is well known that radium is an intermediate product of uranium decay. Rutherford joins, describing the decay process in which radium emits five alpha particles through various intermediate products to end in lead, and speculates that radium-lead decay chains can be used for current rock samples. Boltwood did the hard work, and by the end of 1905 had given the date for 26 separate rock samples, ranging from 92 to 570 million years. He did not publish these results, which were fortunate because they were deformed by measurement errors and poor estimates of the radium beam. Boltwood refined his work and finally published the results in 1907.
Boltwood paper shows that samples taken from comparable layers of layers have the same ratio of lead to uranium, and that samples from older layers have a higher lead proportion, unless there is evidence that lead has run out of samples. His studies are flawed by the fact that the thorium decay series is not understood, which causes incorrect results for samples containing uranium and thorium. However, his calculations were much more accurate than he had ever done at the time. Improvements in this technique will later provide ages for 26 Boltwood samples of 410 million to 2.2 billion years.
Arthur Holmes sets the radiometric dating
Although Boltwood publishes his paper in leading geological journals, the geological community has little interest in radioactivity. Boltwood gave up work on radiometric dating and proceeded to investigate other decay series. Rutherford remained a little curious about Earth-age issues but to no avail.
Robert Strutt tinkered with Rutherford's helium method until 1910 and then stopped. However, Strutt's student, Arthur Holmes became interested in radiometric dating and continued to work on it after others surrendered. Holmes focuses on the main date, as he considers the helium method as unpromising. He made measurements on rock samples and concluded in 1911 that the oldest (sample of Ceylon) was about 1.6 billion years old. This calculation can not be trusted. For example, he assumes that the sample contains only uranium and no lead when they are formed.
More important research was published in 1913. This suggests that the elements generally exist in several variants with different masses, or "isotopes". In the 1930s, the isotopes would be shown to have a nucleus with a number of different neutral particles known as "neutrons". In the same year, another published study established rules for radioactive decay, allowing more precise identification of the decay series.
Many geologists feel this new discovery makes radiometric dating so complex that it is worthless. Holmes felt that they gave him the means to improve his technique, and he stepped forward with his research, publishing before and after the First World War. His work was largely ignored until the 1920s, though in 1917 Joseph Barrell, a professor of geology at Yale, repeated the geologic history as it was understood at that time to conform to Holmes's findings in radiometric dating. Barrell's research determined that strata layers are not all set at the same level, and the current rate of geological change can not be used to provide an accurate timeline of Earth's history.
Holmes's tenacity finally began to pay off in 1921, when speakers at the annual meeting of the British Association for the Advancement of Science reached a rough consensus that Earth was several billion years old, and radiometric dating was credible. Holmes published The Age of the Earth, Introduction to Geological Ideas in 1927 in which it presents a range of 1.6 to 3.0 billion years. There was no great incentive to embrace the radiometric dating that followed, however, and deep-dead people in the geological community stubbornly refused. They never pay attention to the efforts by physicists to disrupt their domain, and have managed to ignore them so far. The growing weight of evidence ultimately tilted the balance in 1931, when the National Research Council of the US National Academy of Sciences decided to resolve questions about the age of the Earth by appointing a committee to be investigated. Holmes, being one of the few people on Earth trained in radiometric dating techniques, is a member of the committee, and actually writes most of the final report.
Thus, Arthur Holmes's report concludes that radioactive dating is the only reliable way to record geological time scales. The biased questions are deflected by extraordinary and precise detail reports. It describes the method used, the treatment with the measurements made, and the error bars and their constraints.
Modern radiometric dating
The radiometric dating continues to be the main way scientists determine the geological time scale. The technique of radioactive dating has been tested and improved on an ongoing basis since the 1960s. Forty different dating techniques have been used up to now, working on a variety of materials. Dates for the same sample using this different technique are very close to the age of the material.
Possible contamination problems do exist, but they have been studied and handled with careful investigation, leading to a minimized sample preparation procedure to limit the likelihood of contamination.
Why meteorites are being used
The age of 4.55 Â ± 0.07 billion years, very close to the age received today, is determined by Clair Cameron Patterson using uranium-lead isotope dating (specifically lead-lead dating) in several meteorites including the Diablo Canyon meteorite and published on 1956.
The age cited by Earth originates, in part, from the Diablo Canyon meteorite for several important reasons and builds on the modern understanding of cosmochemistry that was built over decades of research.
Most geological samples from Earth can not give a direct date from the Earth's formation of the solar nebula because the Earth has undergone differentiation into the core, mantle, and crust, and this has subsequently undergone a long history of mixing and mixing this sample. reservoirs by tectonic plates, weathering and hydrothermal circulation.
All of these processes can affect the isotope dating mechanism because the sample can not always be considered a closed system, meaning either the parent or child nucleus (the atomic species characterized by the number of neutrons and protons). containing atoms) or intermediary child's nuclides may have been removed partially from the sample, which will disguise the date of the resulting isotope. To reduce this effect, usually for some minerals in the same sample, to provide isochron. Alternatively, more than one dating system can be used on the sample to check the date.
Some meteorites are also considered to represent the primitive material from which the formed solar disks are formed. Some have acted as closed systems (for some isotope systems) as soon as solar disks and planets are formed. Until now, this assumption is supported by many scientific observations and repeated isotope dates, and certainly a stronger hypothesis of assumptions that assume terrestrial rocks have retained their original compositions.
However, Archaean ancient ore in galena has been used to determine the formation of the Earth because it is the earliest formation of minerals on the planet and records the earliest homogeneous lead-lead isotope system on the planet. It has returned the date of 4.54 billion years old with the accuracy of at least 1% margin for error.
Statistics for some meteorites that have undergone isochron dating are as follows:
Meteorite Canyon Diablo
The Diablo Canyon meteorite is used because they are large and represent a very rare type of meteorite containing sulphide minerals (mainly troilit, FeS), metallic nickel-iron alloys, plus silicate minerals. This is important because the presence of three mineral phases allows the investigation of isotope dates using samples that provide a large separation in concentrations between parent and child nuclides. This is especially true of uranium and lead. Lead is highly chalkophilic and is found in sulphides at much greater concentrations than in silicates, compared to uranium. Because of this separation in the parent and child nuclides during meteorite formation, this permits a much more precise date from the formation of the solar disk and hence the planets than before.
The prescribed age of the Diablo Canyon meteorite has been confirmed by hundreds of other age determinations, from both terrestrial and other meteorite samples. Meteorite samples, however, show a spread from 4.53-4.5 billion years ago. This is interpreted as the duration of the formation of the solar nebula and its collapse into the solar disk to form the Sun and the planets. This 50-million-year period allows the growth of planets from the sun's dust and native meteorites.
The moon, as another space agency that has not experienced tectonic plates and which lacks atmosphere, provides a reasonably accurate age date from samples returning from the Apollo mission. The stones returning from the Moon have been dated to a maximum of 4.51 billion years. Mars meteorites that have landed on Earth have also been about 4.5 billion years old because lead lead. The moon samples, since they have not been disturbed by weathering, tectonic plates or organism-driven matter, can also provide dating by direct electron microscopy of cosmic ray tracks. The accumulation of dislocations produced by the effects of high energy cosmic ray particles provides another confirmation of the date of the isotope. Cosmic ray displays are useful only on unmelted materials, because they melt the crystal structure of the material, and remove the traces left by the particles.
Overall, the age-dated concordance of both the initial terrestrial lead reservoir and all other reservoirs in the Solar System found to date are used to support the fact that Earth and the rest of the Solar System formed about 4.53 to 4.58 billion years ago.
See also
References
Bibliography
- Dalrymple, G. Brent (1994-02-01). Earth Age . Stanford University Press. ISBNÃ, 0-8047-2331-1.
Further reading
- Baadsgaard, H.; Lerbekmo, J.F.; Wijbrans, J.R., 1993. Multimethod radiometric age for bentonite near the top Baculites reesidei Southwest zone of Saskatchewan (border of Campanian-Maastrichtian stage?). Canada Earth Journal , v.30, p.Ã, 769-775.
- Baadsgaard, H. and Lerbekmo, J.F., 1988. Radiometric age for Cretaceous-Tertiary boundaries based on K-Ar, Rb-Sr, and U-Pb bentonite ages from Alberta, Saskatchewan and Montana. Canada Earth Journal , v.25, p.Ã, 1088-1097.
- Eberth, D.A. and Braman, D., 1990. Stratigraphy, sedimentology, and paleontology of the vertebrates of the Judith River Formation (Campanian) near Lake Muddy, middle-west Saskatchewan. Canadian Petroleum Geological Bulletin , v.38, no.4, pp. 387-406.
- Goodwin, M.B. and Deino, A.L., 1989. The first radiometric age of the Judith River Formation (Upper Cretaceous), Hill County, Montana. Canada Earth Journal , v.26, p.Ã, 1384-1391.
- Gradstein, F. M.; Agterberg, F.P.; Ogg, J.G.; Hardenbol, J.; van Veen, P.; Thierry, J. and Zehui Huang., 1995. Triassic, Jurassic and Cretaceous time scale. IN: Bergren, W. A.Ã,; Kent, D.V.; Aubry, M-P. and Hardenbol, J. (eds.), Geochronology, Time Scale, and Global Stratigraphic Correlation . Society of Paleontologists and Mineralogy of Economics, Special Publication No. 54, p.Ã, 95-126.
- Harland, W.B., Cox, A.V.; Llewellyn, P.G.; Pickton, C.A.G.; Smith, A.G.; and Walters, R., 1982. Geological Time Scale : 1982 edition. Cambridge University Press: Cambridge, 131p.
- Harland, W.B.; Armstrong, R.L.; Cox, A.V.; Craig, L.E.; Smith, A.G.; Smith, D.G., 1990. Geological Time Scale , 1989 edition. Cambridge University Press: Cambridge, p., 1-263. ISBN: 0-521-38765-5
- Harper, C.W., Jr., 1980. Relative age inference in paleontology . Lethaia, v. 13, p. 239-248.
- Obradovich, J.D., 1993. Cretaceous time scale. IN: Caldwell, W.G.E. and Kauffman, E.G. (eds.). Evolution of the Valley of the Western Interior . Canadian Geological Association, Special Paper 39, p. 379-396.
- Palmer, Allison R. (compiler), 1983. Geological Decade of North America 1983 Geology Time Scale. Geology , v. 11, p.Ã, 503-504. September 12, 2004.
- Powell, James Lawrence, 2001, Terra Firma's Mystery: The Age and Evolution of the Earth , Simon & amp; Schuster, ISBN 0-684-87282-X
External links
- TalkOrigins.org
- Vectorsite.net - The initial version of this article is based on the public domain text by Greg Goebel
- USGS preface of the Earth Age
- NASA's exposure of Martian meteorite age
- Charge the Earth at In Our Time on the BBC.
- Pre-1900 Non-Religious Estimates from the Earth Age
Source of the article : Wikipedia
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