Clocks in the Rocks

Uranium Uranium is a fissile isotope of uranium that is bred from thorium as part of the thorium fuel cycle. Uranium was investigated for use in nuclear weapons and as a reactor fuel; however, it was never deployed in nuclear weapons or used commercially as a nuclear fuel. It has a half-life of , years. Uranium is produced by the neutron irradiation of thorium When thorium absorbs a neutron , it becomes thorium , which has a half-life of only 22 minutes. Thorium decays into protactinium through beta decay. Protactinium has a half-life of 27 days and beta decays into uranium ; some proposed molten salt reactor designs attempt to physically isolate the protactinium from further neutron capture before beta decay can occur. Uranium usually fissions on neutron absorption but sometimes retains the neutron, becoming uranium


See Article History Alternative Title: The important characteristic of common lead is that it contains no significant proportion of radiogenic lead accumulated since the time that the mineral or rock phase was formed. Of the four isotopes of lead, two are formed from the uranium isotopes and one is formed from the thorium isotope; only lead is not known to have any long-lived radioactive progenitor. Primordial lead is thought to have been formed by stellar nuclear reactions, released to space by supernovae explosions, and incorporated within the dust cloud that constituted the primordial solar system; the troilite iron sulfide phase of iron meteorites contains lead that approximates the primordial composition.

The lead incorporated within the Earth has been evolving continuously from primordial lead and from the radioactive decay of uranium and thorium isotopes. Thus, the lead isotopic composition of any mineral or rock depends upon its age and the environment from which it was formed; that is, it would depend upon the ratio of uranium plus thorium to lead in the parent material.

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.

While there are numerous natural processes that can serve as clocks, there are also many natural processes that can reset or scramble these time-dependent processes and introduce uncertainties. To try to set a reasonable bound on the age, we could presume that the Earth formed at the same time as the rest of the solar system. If the small masses that become meteorites are part of that system, then a measurement of the solidification time of those meteorites gives an estimate of the age of the Earth.

The following illustration points to a scenario for developing such an age estimate. Some of the progress in finding very old samples of rock on the Earth are summarized in the following comments. It is a compound of zirconium, silicon and oxygen which in its colorless form is used to make brilliant gems. Samples more than 3. Older ages in the neighborhood of 4. The graph below follows the treatment of Krane of Rb-Sr studies of meteorite samples from Wetherill in order to show the nature of the calculation of age from isochrons.

Considering the relative scale of nuclei and atoms , nuclei are so remote from the outer edge of the atoms that no environmental factors affect them.

Radiometric dating

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.

In dating: Fission-track dating during the spontaneous fission of uranium In this unique type of radioactive decay, the nucleus of a single parent uranium atom splits into two fragments of similar mass with such force that a trail of crystal damage is left in the mineral.

E-mail An analysis of the precise NIST atomic mass of the members of a same atomic weight family of isotopes appears to provide some interesting results. Some important and surprising characteristics of nuclear structure seem to be clear, along with some fine-structure hints. Predictions of the half-life or stability of isotopes seem very reliable. The total amount of released energy in a Beta-decay kinetic and photon is also generally reliably known.

Generally, isotopes have always been examined as parts of a family of same-element isotopes. This research was quite different in considering them instead to be parts of families of same-atomic-weight isotopes. Even more significant is the fact that there seems to be very strong evidence that neutrons do not actually exist as neutrons within atomic nuclei! They certainly exist in free space, but the presentation which follows suggests that they cannot exist within the atomic nucleus, that they must instead exist as SEPARATE protons and electrons within the nucleus.

This actually agrees with a long-known fact which seems to have never troubled anyone before. However, such a statement seems to imply that a common method of nuclear decay should be the spontaneous natural emission of a neutron, to enable a nucleus to become more stable. But it has long been known that none of the heaviest nuclei ever decay by emitting a neutron!

Only three known, relatively common isotopes decay by emitting a neutron, 89Br35, 87Br35, and 5He2. The first two of these do not naturally occur and are only produced as fission products of U If discrete neutrons actually existed within all nuclei, it seems logical that at least some nuclei would naturally decay by releasing one or more of them.


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.

The various dating techniques available to archaeologists by Michael G. Lamoureux, March/April Introduction. Today’s archaeologist has a wide variety of natural, electro-magnetic, chemical, and radio-metric dating methodologies available to her that can be used to accurately date objects that are just a few hundred years old as well as objects that are a few million years old with high.

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. The crucial point here is: Accepted Dating Methods Here we outline some dating methods , both absolute and relative, that are widely accepted and used by the scientific community. Absolute dating supplies a numerical date whilst relative dating places events in time-sequence; both are scientifically useful.

Radiometric Dating This is based upon the spontaneous breakdown or decay of atomic nuclei.


A single watch or clock for the entire class will do. Return to top PART 1: After students have decided how to establish the relative age of each rock unit, they should list them under the block, from most recent at the top of the list to oldest at the bottom. The teacher should tell the students that there are two basic principles used by geologists to determine the sequence of ages of rocks.

Uranium-lead is one of the oldest and most refined of the radiometric dating schemes. It can be used over an age range of about 1 million years to over billion .

Hitler, unable to make a living as an artist, turned to earning extra money by serving as an army intelligence agent reporting to a Captain Karl Mayr. The bushy-eyebrowed Hess flew alone to England in May , in an effort to make peace. In August , British military authorities announced that Hess had committed suicide, a judgment that continues to be disputed. Several recent studies of the Hess incident show there was much deeper meaning to this intriguing story, which was only magnified by his sudden and mysterious death just as his release from captivity seemed imminent.

Rudolf Hess was born in Egypt in , the son of a German importer. He was well schooled and well traveled by the time he joined the German Army during World War I, serving in the same regiment as Corporal Adolf Hitler. He was wounded twice and later became a fighter pilot, but the war ended before he could experience much combat. Returning to Munich after the war, Hess helped other ex-servicemen in the paramilitary Freikorps to oust a short-lived Communist local government.

After helping to break the Communist coup, Hess joined the Thule Society and enrolled as a student at the University of Munich, where he met his future wife and the man who was to prove a major influence on both Hitler and himself: Professor General Karl Haushofer. Haushofer became the first ranking Nazi to form relationships with South American governments in anticipation of a war with America. These relationships would prove instrumental in the later escape of war criminals from Europe.

When the coup failed, Hess drove off to Austria, where he was sheltered by members of a paramilitary wing of the Thule Society.


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.

The two uranium isotopes decay at different rates, and this helps make uranium-lead dating one of the most reliable methods because it provides a built-in cross-check.

The letter m is sometimes appended after the mass number to indicate a nuclear isomer , a metastable or energetically-excited nuclear state as opposed to the lowest-energy ground state , for example m 73Ta The common pronunciation of the AZE notation is different from how it is written: For example, 14 C is a radioactive form of carbon, whereas 12 C and 13 C are stable isotopes.

There are about naturally occurring nuclides on Earth, [7] of which are primordial nuclides , meaning that they have existed since the Solar System ‘s formation. Primordial nuclides include 32 nuclides with very long half-lives over million years and that are formally considered as ” stable nuclides “, [7] because they have not been observed to decay. In most cases, for obvious reasons, if an element has stable isotopes, those isotopes predominate in the elemental abundance found on Earth and in the Solar System.

However, in the cases of three elements tellurium, indium, and rhenium the most abundant isotope found in nature is actually one or two extremely long-lived radioisotope s of the element, despite these elements having one or more stable isotopes. Of the nuclides never observed to decay, only 90 of these all from the first 40 elements are theoretically stable to all known forms of decay.

Element 41 niobium is theoretically unstable via spontaneous fission , but this has never been detected. Many other stable nuclides are in theory energetically susceptible to other known forms of decay, such as alpha decay or double beta decay, but no decay products have yet been observed, and so these isotopes are said to be “observationally stable”.

The predicted half-lives for these nuclides often greatly exceed the estimated age of the universe, and in fact there are also 27 known radionuclides see primordial nuclide with half-lives longer than the age of the universe. Adding in the radioactive nuclides that have been created artificially, there are 3, currently known nuclides.


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.

• radiometric dating (which uses the concept of radioactive decay) is the most common method of absolute dating Uranium – Lead Dating Method • Uranium is a radioactive isotope that decays in a series of steps to lead • Half-life of Uranium is billion years.

One kg of fresh water contains Surprisingly the world under water is very much different from that above in the availability of the most important gases for life: Whereas in air about one in five molecules is oxygen, in sea water this is only about 4 in every thousand million water molecules. Whereas air contains about one carbondioxide molecule in air molecules, in sea water this ratio becomes 4 in every million water molecules, which makes carbondioxide much more common available in sea water than oxygen.

Note that even though their concentrations in solution differ due to differences in solubility ability to dissolve , their partial pressures remain as in air, according to Henry’s law, except where life changes this. Plants increase oxygen content while decreasing carbondioxide and animals do the reverse. Bacteria are even capable of using up all oxygen.

How Old is that Rock?