In order to be used as a natural clock to calculate the age of the earth, the processes generating lead isotopes must meet the four conditions of a natural clock: Dalrymple cites examples of lead isotope dating that give an age for the earth of about 4. Lead isotopes are important because two different lead isotopes Pb and Pb are produced from the decay series of two different uranium isotopes U and U. Since both decay series contain a unique set of intermediate radioactive isotopes, and because each has its own half-life, independent age calculations can be made from each Dalrymple The presence of a stable lead isotope that is not the product of any decay series Pb allows lead isotopes to be normalized, allowing for the use of isochrons and concordia-discordia diagrams as dating tools. Two other characteristics of lead isotope measurements make it superior to other methods. First, measuring the isotope ratio of a single element can be done much more precisely than measuring isotope ratios of two differing elements.
Images Radioactive decay All ordinary matter is made up of combinations of chemical elements , each with its own atomic number , indicating the number of protons in the atomic nucleus. Elements exist in different isotopes , with each isotope of an element differing in the number of neutrons in the nucleus. A particular isotope of a particular element is called a nuclide. Some nuclides are naturally unstable.
Definition: The term “ore” is defined in the current study to describe a concentration of non-metallic, e.g., feldspar, or metallic minerals, e.g. spodumene, in pegmatitic rocks irrespective of its structure and position in the deposit which was or is currently mined for a profit.
This false notion is often promoted when radioactive dates are listed with utterly unrealistic error bars. In this report , for example, we are told that using one radioactive dating technique, a lunar rock sample is 4, million years old, plus or minus 23 million years old. Of course, that error estimate is complete nonsense. It refers to one specific source of error — the uncertainty in the measurement of the amounts of various atoms used in the analysis.
Most likely, that is the least important source of error. If those rocks really have been sitting around on the moon for billions of years, I suspect that the the wide range of physical and chemical processes which occurred over that time period had a much more profound effect on the uncertainty of the age determination. This is best illustrated by the radioactive age of a sample of diamonds from Zaire. Their age was measured to be 6. Do you see the problem? Those who are committed to an ancient age for the earth currently believe that it is 4.
Obviously, then, the minimum error in that measurement is 1.
My area of expertise is isotope geochemistry and geochronology. My focus was on the history of secondary mineral deposition largely calcite and silica in soil and unsaturated- and saturated-zone settings and on isotope-geochemical indicators of water-rock interaction as evidence of past water flow. These studies used U-Pb and U-series and other isotope-geochemical methods to characterize the timing of low-temperature surface processes of mineral deposition and to evaluate past water-rock interaction.
In I was closely involved in the installation and detailed testing of a new ThermoFinnigan thermal-ionization mass-spectrometer Triton.
The fact that prior to Ga, Earth’s non-arc-like oceanic basalts have similar incompatible element signatures suggests they come from a relatively unfractionated mantle source similar .
Zircons found from grains in Western Australia are considered slightly older — 4. Geologists depend on radiometric age dating to give dates to different strata and the rocks and bones and artifacts found in those layers. Meteorites During its history, the earth has suffered constant change. Erosion, volcanic eruptions, earthquakes, catastrophes change the surface of the earth, melting rocks, grinding them up and spitting them back out in different forms than they had when they started.
Those who trust in radiometric dating methods point to G. Dalrymple shows that the dates of chondrite samples derived through different methods all give similar ages. A list of samples dated by the rubidium-strontium Rb-Sr method gives dates in a range from 4. Samarium-neodymium Sm-Nd dating of chondrites gives a date of 4. Dalrymple lists other sets of samples and shows that the samples consistently date between 4. This looks like convincing evidence that the earth is truly about 4.
As we noted last week, however, the use of these dating methods depends on a number of assumptions. When these methods give dates hundreds of millions of years apart, even without taking the margins of error into consideration, we can reasonably hesitate to put our full faith in them. On tests of rocks considered much younger, those result differences really matter.
The method compares the amount of a naturally occurring radioactive isotope and its decay products, in samples. The method uses known decay rates. It may be used to date a wide range of natural and man-made materials. Fossils may be dated by taking samples of rocks from above and below the fossil’s original position.
The age of the Earth is ± billion years ( × 10 9 years ± 1%). This age may represent the age of the Earth’s accretion, of core formation, or of the material from which the Earth formed. This dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.
The isochron method Many radioactive dating methods are based on minute additions of daughter products to a rock or mineral in which a considerable amount of daughter-type isotopes already exists. These isotopes did not come from radioactive decay in the system but rather formed during the original creation of the elements. In this case, it is a big advantage to present the data in a form in which the abundance of both the parent and daughter isotopes are given with respect to the abundance of the initial background daughter.
The incremental additions of the daughter type can then be viewed in proportion to the abundance of parent atoms. In mathematical terms this is achieved as follows. This term, shown in Figure 1, is called the initial ratio. The slope is proportional to the geologic age of the system. In practice, the isochron approach has many inherent advantages. When a single body of liquid rock crystallizes, parent and daughter elements may separate so that, once solid, the isotopic data would define a series of points, such as those shown as open circles designated R1, R2, R3 in Figure 1.
With time each would then develop additional daughter abundances in proportion to the amount of parent present.
Evidence for Evolution and Old Earth, A Catholic Perspective
Zircons found from grains in Western Australia are considered slightly older – 4. Geologists depend on radiometric age dating to give dates to different strata and the rocks and bones and artifacts found in those layers. Most will say that the dating methods have been confirmed over and over again, but there are questions about whether the dating methods used are reliable and whether they give scientists true dates – or whether they give dates that fit those secular geologists’ preconceived ideas.
During its history, the earth has suffered constant change. Erosion, volcanic eruptions, earthquakes, catastrophes change the surface of the earth, melting rocks, grinding them up and spitting them back out in different forms than they had when they started.
martindale’s calculators on-line center archaeology, anthropology, paleoichnology – palaeoichnology – neoichnology, paleobiology – palaeobiology, paleobotany – palaeobotany, paleoclimatology – palaeoclimatology.
Evidence for Evolution and an Old Earth Evidence for Evolution and an Old Earth, a Catholic Perspective “According to the widely accepted scientific account, the universe erupted 15 billion years ago in an explosion called the ‘Big Bang’ and has been expanding and cooling ever since. Later there gradually emerged the conditions necessary for the formation of atoms, still later the condensation of galaxies and stars, and about 10 billion years later the formation of planets.
In our own solar system and on earth formed about 4. While there is little consensus among scientists about how the origin of this first microscopic life is to be explained, there is general agreement among them that the first organism dwelt on this planet about 3. Since it has been demonstrated that all living organisms on earth are genetically related, it is virtually certain that all living organisms have descended from this first organism. Converging evidence from many studies in the physical and biological sciences furnishes mounting support for some theory of evolution to account for the development and diversification of life on earth, while controversy continues over the pace and mechanisms of evolution.
While the story of human origins is complex and subject to revision, physical anthropology and molecular biology combine to make a convincing case for the origin of the human species in Africa about , years ago in a humanoid population of common genetic lineage.
A SECOND DEBATE WITH A CREATIONIST Originally posted on
Godthelp in Hill, Robert S. White, , The Nature of Hidden Worlds: Australian Conservation Foundation, Melbourne. Michael Archer, Suzanne J.
The two elements are joined in a parent—daughter relationship by the alpha decay of Sm to Nd with a half-life of 1. Some of the Sm may itself have originally been produced through alpha-decay from Gd , which has a half-life of 1. To find the date at which a rock or group of rocks formed one can use the method of isochron dating. From the slope of the “isochron” line through these points the date of formation can be determined. Alternatively, one can assume that the material formed from mantle material which was following the same path of evolution of these ratios as chondrites , and then again the time of formation can be calculated see The CHUR model.
Samarium is accommodated more easily into mafic minerals, so a mafic rock which crystallises mafic minerals will concentrate neodymium in the melt phase relative to samarium. Thus, as a melt undergoes fractional crystallization from a mafic to a more felsic composition, the abundance of Sm and Nd changes, as does the ratio between Sm and Nd. The importance of this process is apparent in modeling the age of continental crust formation.
The CHUR model[ edit ] Through the analysis of isotopic compositions of neodymium, DePaolo and Wasserburg  discovered that terrestrial igneous rocks at the time of their formation from melts closely followed the ” chondritic uniform reservoir ” or “chondritic unifractionated reservoir” CHUR line — the way the Nd: Chondritic meteorites are thought to represent the earliest unsorted material that formed in the Solar system before planets formed.