Reference to a case where the given method did not work This is perhaps the most common objection of all. Creationists point to instances where a given method produced a result that is clearly wrong, and then argue that therefore all such dates may be ignored. Such an argument fails on two counts: First, an instance where a method fails to work does not imply that it does not ever work. The question is not whether there are “undatable” objects, but rather whether or not all objects cannot be dated by a given method. The fact that one wristwatch has failed to keep time properly cannot be used as a justification for discarding all watches. How many creationists would see the same time on five different clocks and then feel free to ignore it?
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.
It follows that uranium-lead, potassium-argon (K-Ar), and Rubidium-Strontium (Rb-Sr) decay can be used for very long time periods, whilst radiocarbon dating can only be used up to about 70, years.
Example[ edit ] For example, consider the case of an igneous rock such as a granite that contains several major Sr-bearing minerals including plagioclase feldspar , K-feldspar , hornblende , biotite , and muscovite. Rubidium substitutes for potassium within the lattice of minerals at a rate proportional to its concentration within the melt. The ideal scenario according to Bowen’s reaction series would see a granite melt begin crystallizing a cumulate assemblage of plagioclase and hornblende i.
This then causes orthoclase and biotite, both K rich minerals into which Rb can substitute, to precipitate. The resulting Rb-Sr ratios and Rb and Sr abundances of both the whole rocks and their component minerals will be markedly different. This, thus, allows a different rate of radiogenic Sr to evolve in the separate rocks and their component minerals as time progresses. Calculating the age[ edit ] The age of a sample is determined by analysing several minerals within the sample.
If these form a straight line then the samples are consistent, and the age probably reliable. The slope of the line dictates the age of the sample. Several preconditions must be satisfied before a Rb-Sr date can be considered as representing the time of emplacement or formation of a rock. Rb and Sr are relatively mobile alkaline elements and as such are relatively easily moved around by the hot, often carbonated hydrothermal fluids present during metamorphism or magmatism.
Conversely, these fluids may metasomatically alter a rock, introducing new Rb and Sr into the rock generally during potassic alteration or calcic albitisation alteration. Rb-Sr can then be used on the altered mineralogy to date the time of this alteration, but not the date at which the rock formed.
The Age of the Earth
At the time that Darwin’s On the Origin of Species was published, the earth was “scientifically” determined to be million years old. By , it was found to be 1. In , science firmly established that the earth was 3.
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 .
Slowly and painstakingly, geologists have assembled this record into the generalized geologic time scale shown in Figure 1. This was done by observing the relative age sequence of rock units in a given area and determining, from stratigraphic relations, which rock units are younger, which are older, and what assemblages of fossils are contained in each unit. Using fossils to correlate from area to area, geologists have been able to work out a relative worldwide order of rock formations and to divide the rock record and geologic time into the eras, periods, and epochs shown in Figure 1.
The last modification to the geologic time scale of Figure 1 was in the s, before radiometric dating was fully developed, when the Oligocene Epoch was inserted between the Eocene and the Miocene. Although early stratigraphers could determine the relative order of rock units and fossils, they could only estimate the lengths of time involved by observing the rates of present geologic processes and comparing the rocks produced by those processes with those preserved in the stratigraphic record.
With the development of modern radiometric dating methods in the late s and s, it was possible for the first time not only to measure the lengths of the eras, periods, and epochs but also to check the relative order of these geologic time units. Radiometric dating verified that the relative time scale determined by stratigraphers and paleontologists Figure 1 is absolutely correct, a result that could only have been obtained if both the relative time scale and radiometric dating methods were correct.
Nonetheless, stratigraphy and radiometric dating of Precambrian rocks have clearly demonstrated that the history of the Earth extends billions of years into the past. Radiometric dating has not been applied to just a few selected rocks from the geologic record.
This age is obtained from radiometric dating and is assumed by evolutionists to provide a sufficiently long time-frame for Darwinian evolution. And OE Christians theistic evolutionists see no problem with this dating whilst still accepting biblical creation, see Radiometric Dating – A Christian Perspective. This is the crucial point: Some claim Genesis in particular, and the Bible in general looks mythical from this standpoint. A full discussion of the topic must therefore include the current scientific challenge to the OE concept.
Dating – Rubidium–strontium method: The radioactive decay of rubidium (87Rb) to strontium (87Sr) was the first widely used dating system that utilized the isochron method. Rubidium is a relatively abundant trace element in Earth’s crust and can be found in many common rock-forming minerals in which it substitutes for the major element potassium.
These are K-Ar data obtained on glauconite, a potassium-bearing clay mineral that forms in some marine sediment. Woodmorappe fails to mention, however, that these data were obtained as part of a controlled experiment to test, on samples of known age, the applicability of the K-Ar method to glauconite and to illite, another clay mineral. He also neglects to mention that most of the 89 K-Ar ages reported in their study agree very well with the expected ages. Evernden and others 43 found that these clay minerals are extremely susceptible to argon loss when heated even slightly, such as occurs when sedimentary rocks are deeply buried.
As a result, glauconite is used for dating only with extreme caution. The ages from the Coast Range batholith in Alaska Table 2 are referenced by Woodmorappe to a report by Lanphere and others Whereas Lanphere and his colleagues referred to these two K-Ar ages of and million years, the ages are actually from another report and were obtained from samples collected at two localities in Canada, not Alaska.
There is nothing wrong with these ages; they are consistent with the known geologic relations and represent the crystallization ages of the Canadian samples.
References Generic Radiometric Dating The simplest form of isotopic age computation involves substituting three measurements into an equation of four variables, and solving for the fourth. The equation is the one which describes radioactive decay: The variables in the equation are:
The age of the earth can be measured by numerous different techniques, most of which provide just a minimum age. The absolute age of the earth has been most accurately measured through radioactive decay of its rocks.
Rubidium—strontium method The radioactive decay of rubidium 87Rb to strontium 87Sr was the first widely used dating system that utilized the isochron method. Because rubidium is concentrated in crustal rocks, the continents have a much higher abundance of the daughter isotope strontium compared with the stable isotopes. A ratio for average continental crust of about 0. This difference may appear small, but, considering that modern instruments can make the determination to a few parts in 70, , it is quite significant.
Dissolved strontium in the oceans today has a value of 0. Thus, if well-dated, unaltered fossil shells containing strontium from ancient seawater are analyzed, changes in this ratio with time can be observed and applied in reverse to estimate the time when fossils of unknown age were deposited. Dating simple igneous rocks The rubidium—strontium pair is ideally suited for the isochron dating of igneous rocks.
As a liquid rock cools, first one mineral and then another achieves saturation and precipitates, each extracting specific elements in the process. Strontium is extracted in many minerals that are formed early, whereas rubidium is gradually concentrated in the final liquid phase. In practice, rock samples weighing several kilograms each are collected from a suite of rocks that are believed to have been part of a single homogeneous liquid prior to solidification.
The samples are crushed and homogenized to produce a fine representative rock powder from which a fraction of a gram is withdrawn and dissolved in the presence of appropriate isotopic traces, or spikes. Strontium and rubidium are extracted and loaded into the mass spectrometer, and the values appropriate to the x and y coordinates are calculated from the isotopic ratios measured.
The Radiometric Dating Game Radiometric dating methods estimate the age of rocks using calculations based on the decay rates of radioactive elements such as uranium, strontium, and potassium. On the surface, radiometric dating methods appear to give powerful support to the statement that life has existed on the earth for hundreds of millions, even billions, of years. We are told that these methods are accurate to a few percent, and that there are many different methods.
We are told that of all the radiometric dates that are measured, only a few percent are anomalous. This gives us the impression that all but a small percentage of the dates computed by radiometric methods agree with the assumed ages of the rocks in which they are found, and that all of these various methods almost always give ages that agree with each other to within a few percentage points.
The rubidium-strontium dating method is a radiometric dating technique used by scientists to determine the age of rocks and minerals from the quantities they contain of specific isotopes of rubidium (87 Rb) and strontium (87 Sr, 86 Sr).. Development of this process was aided by German chemists Otto Hahn and Fritz Strassmann, who later went on to discover nuclear fission in December
Several Christian ministries promote the idea that the earth is less than 10, years old, which they say comes from the Bible. In reality, the Bible makes no claim as to the age of the earth, although it does establish a minimum age. This page examines some of the history of the controversy—what the Bible actually says and does not say—and the scientific evidence surrounding the age of the earth. Age of the earth according to the Bible The following is a summary of the biblical evidence presented on this website regarding the age of the earth.
For more detailed explanations of each topic, please click on the associated link. History of the age of the earth As indicated earlier, the Bible does not fix the age of the earth, contrary to the claims of Answers in Genesis. Archbishop Ussher took the genealogies of Genesis, assuming they were complete, and calculated all the years to arrive at a date for the creation of the earth on Sunday, October 23, B. There are a number of other assumptions implicit in the calculation. The first, and foremost, assumption is that the genealogies of Genesis are complete, from father to son throughout the entire course of human existence.
The second assumption is that the Genesis creation “days” were exactly hours in length. It turns out that both assumptions are false. Incomplete genealogies Biblical Genealogies Although Archbishop Ussher assumed the Genesis genealogies were complete, it is clear from the rest of the Bible that those genealogies were telescoped some names were left out for the sake of brevity , which is common in biblical genealogies but rare in modern genealogies.
How Old is the Earth
Shirey and James E. The loose crystals range from 1. Photo by Orasa Weldon. ABSTRACT It has been more than two decades since diamond ages have proven to be up to billions of years older than their host magmas of kimberlite or lamproite.
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.
Methods of Dating the Age of Meteorites Meteorites are among the oldest objects we know about – formed about 4. But how do scientists know this? This article describes the principles and methods used to make that determination. There are well-known methods of finding the ages of some natural objects. Trees undergo spurts in growth in the spring and summer months while becoming somewhat dormant in the fall and winter months.
When a tree is cut down, these periods are exhibited in a cross section of the trunk in the form of rings. Simply counting the number of rings will give one a fairly good idea of the age of the tree. Periods of heavy rain and lots of sunshine will make larger gaps of growth in the rings, while periods of drought might make it difficult to count individual rings.
The isotopes[ edit ] There are three isotopes used in Rb-Sr dating. It produces the stable daughter isotope 87Sr strontium by beta minus decay. The third isotope we need to consider is 86Sr, which is stable and is not radiogenic , meaning that in any closed system the quantity of 86Sr will remain the same. As rubidium easily substitutes chemically for potassium, it can be found doing so in small quantities in potassium-containing minerals such as biotite , potassium feldspar , and hornblende.
martindale’s calculators on-line center archaeology, anthropology, paleoichnology – palaeoichnology – neoichnology, paleobiology – palaeobiology, paleobotany – palaeobotany, paleoclimatology – palaeoclimatology.
Landsat Image provided by Ronald W. Lunar and Planetary Science XX, pp. Impact evidence from Massignano, Arcona. Dense fluid inclusions and their petrological significance abstract. Russian , Mineralogicheskii Zhurnal, v. International Geology Review, v. Geological Society of America, Special Paper , pp. Mineralogicheskoye Obshchestvo Zapiski, v. Large Meteorite Impacts and Planetary Evolution,. Geochemical Characteristics of the Melt Coatings, Meteoritics; vol.
Geochemistry of rocks from the Chesapeake Bay crater and North American tektites abstract. Meteoritics and Planetary Science, v 33, n 4, p A90 – New sites, nature of the strewn field, Ir data, and discovery of coesite and shocked quartz, Special Paper of the Geological Society of America, Issue , pp. Leningrad, Nedra, p.