Important We believe any unbiased reader will realize that we were fair with our treatment of the two models in the table above. Yet, although the theory of evolution matches the facts in some cases, evolution is still an unproven theory. By now, you may believe it should be your first choice also. Unlike many others that preceded us, we attempted to find a clear defense of evolution for two reasons: To keep from being accused of bias. To keep from making claims that someone could refute later.
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. Finally in , it was discovered that the earth is “really” 4. In these early studies the order of sedimentary rocks and structures were used to date geologic time periods and events in a relative way. At first, the use of “key” diagnostic fossils was used to compare different areas of the geologic column.
Index, Illustration, Reference, and Photo Credit. A B C D E F G H I J K L | (go to 2nd index page) M N O P Q R S T U V W X Y Z.
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.
Inteendeel, meeste sillabusse in skole en universiteite aanvaar die konsep van evolusie as die wetenskaplike basis vir die verstaan van die fisiese kosmos soos ons dit vandag ken. A gradual process in which something changes into a different and usually more complex or better form. See Synonyms at development. The process of developing.
Change in the genetic composition of a population during successive generations, as a result of natural selection acting on the genetic variation among individuals, and resulting in the development of new species.
The generally accepted age for the Earth and the rest of the solar system is about billion years (plus or minus about 1%). This value is derived from several.
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. When determining the ages of very old objects, the only suitable clocks we have found involve the measurement of decay products of radioactive isotopes.
Isotopes are atoms of the same element with different amounts of neutrons. Some isotopes are stable, whereas others are radioactive and decay into other components called daughter isotopes. For example, hydrogen has two stable isotopes 1H ordinary hydrogen , 2H deuterium , and one radioactive isotope 3H tritium.
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.
A brief introduction to isochron dating methodology. The technique (and related ones) is widely used in isotope geology.
Abstract Documenting the early tectonic and magmatic evolution of the Izu—Bonin—Mariana IBM arc system in the Western Pacific is critical for understanding the process and cause of subduction initiation along the current convergent margin between the Pacific and Philippine Sea plates. Ocean floor drilling International Ocean Discovery Program Expedition recovered basement-forming, low-Ti tholeiitic basalt crust formed shortly after subduction initiation but distal from the convergent margin nominally reararc of the future IBM arc Amami Sankaku Basin: Radiometric dating of this basement gives an age range Similarity in age range and geochemical character between the reararc and forearc basalts implies that the ocean crust newly formed by seafloor spreading during subduction initiation extends from fore- to reararc of the present-day IBM arc.
Given the age difference between the oldest forearc basalt and the ASB crust, asymmetric spreading caused by ridge migration might have taken place. This scenario for the formation of the ASB implies that the Mesozoic remnant arc terrane of the Daito Ridges comprised the overriding plate at subduction initiation.
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.
Creation Versus Evolution: We compare the theory of evolution with the Bible’s creation account in easy-to-understand terms, using evidence from the fields of paleontology, geology, biology, and provide links and a bibliography for those who want to study both sides of the issue.
Idealized and simplified diagram of the Grand Canyon There are a number of lava flows on the plateau that the canyon is cut into yellow in Figure 1, above. These lava flows are Cenozoic in age, and some of them spill into the canyon. The walls of the canyon are mostly cut into horizontal rock layers of Paleozoic age green in Figure 1, above. There is an angular unconformity at the bottom of the Paleozoic layers. An angular unconformity is the result of tilting and eroding of the lower layers before the upper ones are deposited.
These tilted and eroded layers are Precambrian in age blue in Figure 1, above. The geological relationships of the various formations are quite clear. The lava flows which spill into the canyon must be younger than the canyon. The canyon must be younger than the rock layers that it cuts into. The sediments above the angular unconformity must be younger than the sediments below it.
The ordering of events which resulted in Figure 1 must be: The blue layers are deposited.
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.
Radiometric dating or radioactive dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay.
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. Since then, there have been significant advances in the analysis of diamonds and their mineral inclusions, in the understanding of diamond-forming fluids in the mantle, and in the relationship of diamonds to the deep geology of the continents and the convecting mantle.
The occurrence of natural diamonds is remarkable and important to earth studies. This article reviews current thinking of where, how, when, and why natural diamonds form. Analytical advances, improved geologic knowledge, and the emergence of new diamond-producing regions such as the Slave craton of Canada have all contributed to this change.
The most prized specimens for research are flawed with visible inclusions figure 2 , for these carry actual samples of mantle minerals from depths as great as km beneath the surface. Diamond provides the perfect container for mantle minerals, isolating them from the high pressure and temperature reactions within the earth for geologic time scales. Even low elemental concentrations and minute features in diamond can now be analyzed using instruments with higher sensitivity and resolution.
As a result, study combining the inclusion and its diamond host is a powerful tool for geologic research, which itself has improved our understanding of diamond formation.
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.
40 Ar/ 39 Ar dating reveals a ± Ma age for the basement of the Izu–Bonin–Mariana arc.. The arc basement is oceanic crust formed at or soon after subduction initiation. • A spreading ridge following subduction initiation migrated away from the trench.
Manicouagan crater, Quebec, Canada is visible in the background. Exhumed paleoplains of the Precambrian shield of North America. American Journal of Science, , — The viscous flow behavior of diaplectic glass and fusion-formed glass: A Comparitive study on shocked anorthosite from Manicouagan crater, Canada. Diaplectic glass and fusion-formed glass: Comparative studies on shocked anorthosite from Manicouagan crater, Canada.
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: Pnow – The quantity of the parent isotope that remains now.
The Planetary and Space Science Centre (PASSC) opened in April, and was the first facility of its kind in Canada.
March 28, This post is about elevation measurements for exposure-dating samples, and how accurate they need to be. Basically, the main thing that controls cosmogenic-nuclide production rates is site elevation, or, more precisely, atmospheric pressure — at higher elevation, there is less atmosphere between you and the extraterrestrial cosmic-ray flux, so the production rate is higher. Thus, to compute the cosmogenic-nuclide production rate at a sample site, the first thing we need to know is the elevation.
Once we know the elevation, we can convert it to a mean atmospheric pressure using a model for how the atmospheric pressure varies with elevation, and then compute the production rate. The second one — converting an elevation to a mean atmospheric pressure during the exposure duration of the sample — is actually a fairly complicated problem and is the subject of another post , as well as a fairly large number of papers.
However, the first one — accurately measuring the elevation — ought to be pretty simple.