Leibnitz reworked Descartes’s cosmogony. Protogea was published much later in An essay toward a Natural History of the Earth. Woodward came down fairly strongly for the view that the flood was an act of God that could not be accounted for by normal physical processes. He also postulated hydrological sorting to account for the ordering of fossils. Whiston added comets to Burnet’s cosmogony as the source of the waters of the flood. Lectures and Discourse of Earthquakes and Subterranean Eruptions. Hooke believed that the fossils were the remains of extinct species and could not be accounted for by the Flood.

Changing Views of the History of the Earth

See Article History Fission-track dating, method of age determination that makes use of the damage done by the spontaneous fission of uranium , the most abundant isotope of uranium. The fission process results in the release of several hundred million electron volts of energy and produces a large amount of radiation damage before its energy is fully absorbed. The damage, or fission tracks, can be made visible by the preferential leaching removal of material by solution of the host substance with a suitable chemical reagent; the leaching process allows the etched fission-track pits to be viewed and counted under an ordinary optical microscope.

Thorium (Th), radioactive chemical element of the actinoid series of the periodic table, atomic number 90; it is a useful nuclear reactor fuel. Thorium was discovered () by Swedish chemist Jöns Jacob is silvery white but turns gray or black on exposure to air. It is about half as abundant as lead and is three times more abundant than uranium in Earth’s crust.

Thorium, also, is potentially of great economic value, because one of its isotopes, thorium , can be converted into the fissionable isotope uranium in a nuclear breeder reactor i. This and other physical properties such as melting and boiling points are greatly affected by small amounts of certain impurities, such as carbon and thorium dioxide.

Thorium is added to magnesium and magnesium alloys to improve their high-temperature strength. It has been used in commercial photoelectric cells for measuring ultraviolet light of wavelengths ranging from to angstroms. Added to glass , thorium yields glasses with a high refractive index , useful for specialized optical applications. It was formerly in great demand as a component of mantles for gas and kerosene lamps and has been used in the manufacture of tungsten filaments for lightbulbs and vacuum tubes.

Natural thorium is a mixture of radioactive isotopes , predominantly the very long-lived thorium 1. Other isotopes occur naturally in the uranium and actinium decay series , and thorium is present in all uranium ores. Thorium is useful in breeder reactors because on capturing slow-moving neutrons it decays into fissionable uranium Synthetic isotopes have been prepared; thorium 7, year half-life , formed in the decay chain originating in the synthetic actinoid element neptunium , serves as a tracer for ordinary thorium thorium The dioxide ThO2 , a very refractory substance, has many industrial applications; thorium nitrate has been available as a commercial salt.


NORM results from activities such as burning coal, making and using fertilisers, oil and gas production. Uranium mining exposes those involved to NORM in the uranium orebody. Radon in homes is one occurrence of NORM which may give rise to concern and action to control it, by ventilation.

Thorium (Th), radioactive chemical element of the actinoid series of the periodic table, atomic number 90; it is a useful nuclear reactor fuel. Thorium was discovered () by Swedish chemist Jöns Jacob is silvery white but turns gray or black on exposure to air. It is about half as abundant as lead and is three times more abundant than uranium in Earth’s crust.

Red horse head, below and to the left of the yellow horse heads. These horse heads and signs are in a small alcove, above a flat floor. Just a few lines have been used to outline more clearly the shape of a small mammoth, about 20 cm wide, taken up by the flowstone or stalagmite cascade at the entrance to the Brunel Chamber. I have highlighted the shape in the right hand photograph. The zone is heavily covered with calcite. It is not possible to determine whether the front of this animal existed at one time.

Length ca 40 cm. I had noticed in several images that the artist s used natural irregularities in the surfaces to emphasize a three-dimensional appearance. I wonder if some of the odd placements of the figures is because the artist saw something to add to the realism of his picture. So when I saw the ‘headless’ ibex, I immediately thought that the other side of the crevice suggested the head.

Then I saw that the crevice itself forms the line of the shoulder completed by a short line of red and the front legs where it splits into an inverted Y. One leg is fairly straight and is paralleled by the drawn hind leg. The other front leg is raised and curled in a prancing mid-step, complete with cloven hoof small inverted V. Just below the raised leg I think I see faint red ochre smudging that has washed down and away.


Because uranium ores emit radon gas, and their harmful and highly radioactive daughter products , uranium mining is significantly more dangerous than other already dangerous hard rock mining Uranium is a chemical element in the periodic table that has the symbol U and atomic number Heavy, silvery-white, toxic, metallic , and naturally- radioactive , uranium belongs to the actinide series and its isotope U is used as the fuel for nuclear reactors and the explosive material for nuclear weapons.

Uranium is commonly found in very small amounts in rocks , soil , water , plants , and animals including humans. Notable characteristics When refined, uranium is a silvery white, weakly radioactive metal, which is slightly softer than steel. It is malleable, ductile, and slightly paramagnetic. When finely divided, it can react with cold water; in air, uranium metal becomes coated with uranium oxide.

Before more precise absolute dating tools were possible, researchers used a variety of comparative approaches called relative dating. These methods — some of which are still used today — provide only an approximate spot within a previously established sequence: Think of it as ordering rather than dating.

Bulk properties[ edit ] Thorium is a moderately soft , paramagnetic , bright silvery radioactive actinide metal. In the periodic table , it lies to the right of actinium , to the left of protactinium , and below cerium. Pure thorium is very ductile and, as normal for metals, can be cold-rolled , swaged , and drawn. Aluminium ‘s is At the start of period 7 , from francium to thorium, the melting points of the elements increase as in other periods , because the number of delocalised electrons each atom contributes increases from one in francium to four in thorium, leading to greater attraction between these electrons and the metal ions as their charge increases from one to four.

After thorium, there is a new downward trend in melting points from thorium to plutonium , where the number of f electrons increases from about 0. The major impurity is usually thorium dioxide ThO2 ; even the purest thorium specimens usually contain about a tenth of a percent of the dioxide. Addition of small proportions of thorium improves the mechanical strength of magnesium , and thorium-aluminium alloys have been considered as a way to store thorium in proposed future thorium nuclear reactors.

Thorium forms eutectic mixtures with chromium and uranium, and it is completely miscible in both solid and liquid states with its lighter congener cerium. Isotopes of thorium All but two elements up to bismuth element 83 have an isotope that is practically stable for all purposes “classically stable” , with the exceptions being technetium and promethium elements 43 and All elements from polonium element 84 onward are measurably radioactive.

Age of the Earth: strengths and weaknesses of dating methods

Stratigraphic unit numbers are shown on the left, and the cultural horizons are highlighted in gray. Clovis ages have been reported elsewhere see text. No HF etching was applied. An initial equivalent dose De estimate was made by comparing the natural OSL signal of four aliquots to their OSL signal after a given dose. A second identical regenerative dose was applied to the same four aliquots, and the Infrared Stimulated Luminescence IRSL signal was measured as a check for feldspar contamination.

Uranium–lead dating, abbreviated U–Pb dating, is one of the oldest and most refined of the radiometric dating schemes. It can be used to date rocks that formed and crystallised from about 1 million years to over billion years ago with routine precisions in the –1 percent range.. The dating method is usually performed on the mineral zircon.

This thing all things devours: Birds, beasts, trees, flowers; Grinds hard stones to meal; Slays kings, ruins town, And beats high mountain down. This riddle exemplifies how time normally results in decay and destruction. So, why are people so interested in the topic of time? Perhaps the biggest reason is because of evil: Humans have a limited lifespan to get things done, so we try to synchronize schedules in order not to waste time. We have a limited endurance for boredom or pain, so before the use of anesthesia, the best surgeons were the quickest.

Although some complain that the Lord delays His coming Mt The best they have is consciousness with a limited ability for such movement providing memories of past times and hopeful pictures of future times.


Decay routes[ edit ] The above uranium to lead decay routes occur via a series of alpha and beta decays, in which U with daughter nuclides undergo total eight alpha and six beta decays whereas U with daughters only experience seven alpha and four beta decays. The term U—Pb dating normally implies the coupled use of both decay schemes in the ‘concordia diagram’ see below. However, use of a single decay scheme usually U to Pb leads to the U—Pb isochron dating method, analogous to the rubidium—strontium dating method.

Finally, ages can also be determined from the U—Pb system by analysis of Pb isotope ratios alone. This is termed the lead—lead dating method.

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.

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.

This challenge is mainly headed by Creationism which teaches a young-earth YE theory. A young earth is considered to be typically just 6, years old since this fits the creation account and some dating deductions from Genesis.


It is ductile, malleable , and capable of taking a high polish. In air the metal tarnishes and when finely divided breaks into flames. It is a relatively poor conductor of electricity. The formulation of the periodic system by Russian chemist Dmitry Mendeleyev in focused attention on uranium as the heaviest chemical element, a position that it held until the discovery of the first transuranium element neptunium in In the French physicist Henri Becquerel discovered in uranium the phenomenon of radioactivity , a term first used in by French physicists Marie and Pierre Curie.

Background. Initially identified in , excavation at Area 15 of the Gault Site was undertaken to explore evidence of early cultures in Central ch focused on the manufacturing technologies, their relationship to Clovis, and the associated age of this assemblage.

Everything Worth Knowing About Scientific Dating Methods This dating scene is dead. The good dates are confirmed using at least two different methods, ideally involving multiple independent labs for each method to cross-check results. Sometimes only one method is possible, reducing the confidence researchers have in the results.

Methods fall into one of two categories: These methods — some of which are still used today — provide only an approximate spot within a previously established sequence: Think of it as ordering rather than dating. One of the first and most basic scientific dating methods is also one of the easiest to understand. Paleontologists still commonly use biostratigraphy to date fossils, often in combination with paleomagnetism and tephrochronology.

A submethod within biostratigraphy is faunal association: Sometimes researchers can determine a rough age for a fossil based on established ages of other fauna from the same layer — especially microfauna, which evolve faster, creating shorter spans in the fossil record for each species. The polarity is recorded by the orientation of magnetic crystals in specific kinds of rock, and researchers have established a timeline of normal and reversed periods of polarity.

How Old is that Rock?