Clocks in the Rocks


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.

Uranium: What It It

Wikimedia Commons To produce fuel-grade uranium, the uranium has to be processed to produce uranium dioxide and to enrich or concentrate the U in the fuel pellets. During this processing, depleted uranium DU , enriched in U and depleted in U , is produced. DU and enriched uranium have numerous civilian and military uses. Since U is the most radioactive isotope of uranium, the removal of it to makes DU the least radioactive phase of uranium, but it still has heavy metal toxicity issues.

Determination of the Decay Constants and Half-Lives of Uranium (U) and Uranium (U), and the Implications for U-Pb and Pb-Pb Radioisotope Dating Methodologies Andrew Snelling, Answers in Genesis, PO Box , Hebron, Kentucky Abstract.

In a typical nuclear reactor, up to one-third of the generated power does come from the fission of Pu, which is not supplied as a fuel to the reactor, but rather, produced from U. Breeder reactors[ edit ] U is not usable directly as nuclear fuel , though it can produce energy via “fast” fission. Depending on design, this process can contribute some one to ten percent of all fission reactions in a reactor, but too few of the about 2.

Breeder reactors carry out such a process of transmutation to convert the fertile isotope U into fissile Pu It has been estimated that there is anywhere from 10, to five billion years worth of U for use in these power plants. Russia has planned to build another unit, BN , at the Beloyarsk nuclear power plant. Also, Japan’s Monju breeder reactor is planned to be started, having been shut down since , and both China and India have announced plans to build nuclear breeder reactors.

However, after safety and design hazards were uncovered, in the Japanese government ordered the decommissioning of the Monju reactor which may be completed by The breeder reactor as its name implies creates even larger quantities of Pu than the fission nuclear reactor. This design is still in the early stages of development. Radiation shielding[ edit ] U is also used as a radiation shield — its alpha radiation is easily stopped by the non- radioactive casing of the shielding and the uranium’s high atomic weight and high number of electrons are highly effective in absorbing gamma rays and x-rays.

It is not as effective as ordinary water for stopping fast neutrons. Both metallic depleted uranium and depleted uranium dioxide are used for radiation shielding. Uranium is about five times better as a gamma ray shield than lead , so a shield with the same effectiveness can be packed into a thinner layer.

The Age of the Earth

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.

The existence of two ‘parallel’ uranium–lead decay routes ( U to Pb and U to Pb) leads to multiple dating techniques within the overall U–Pb system. The term U–Pb dating normally implies the coupled use of both decay schemes in the ‘concordia diagram’ (see below).

When an igneous melt crystallizes, parent and daughter elements are chemically separated into different crystals. Further radioactive decay keeps the parent and daughter elements in the same crystal. Setting the Radiometric Clock Individual crystals of the same mineral are dated to give the age of crystallization or cooling. Examples include zircon, muscovite, and biotite.

Note that whole rock analysis would not give the age of cooling. Setting the Radiometric Clock Carbon is different in that it occurs in organic remains rather than in rocks. Clock is set when an organism dies.

UCSB Science Line

What about carbon dating? Life of 5, at the Beloyarsk nuclear dating rocks with uranium plant. With less carbon; 10 at the Wayback Machine. The mean lifetime of U is 1. Radiocarbon dating is becoming increasingly important in interpreting the past. One should know how the technique works, radiocarbon ages do not increase steadily with depth, figure 1:

Uranium-Thorium dating is based on the detection by mass spectrometry of both the parent ( U) and daughter ( Th) products of decay, through the emission of an alpha particle. The decay of Uranium to Thorium is part of the much longer decay series begining in U and ending in Pb.

Uranium is also referred to as ” depleted uranium ”. Each radioactive element on the list gives off either alpha radiation or beta radiation — and sometimes gamma radiation too — thereby transforming itself into the next element on the list. When uranium ore is extracted from the earth, most of the uranium is removed from the crushed rock during the milling process, but the radioactive decay products are left in the tailings.

Thus 85 percent of the radioactivity of the original ore is discarded in the mill tailings. Depleted uranium remains radioactive for literally billions of years, and over these long periods of time it will continue to produce all of its radioactive decay products; thus depleted uranium actually becomes more radioactive as the centuries and millennia go by because these decay products accumulate.

The horizontal bar beside the name of each decay product indicates the ” half life ” of that particular substance, measured on a logarithmic scale each half-inch to the right represents multiplication by a factor of one thousand. Lead , the last element on the list, is not radioactive. It does not decay, and therefore has no half-life. What is the ”half-life” of a radioactive element? The half-life of a radioactive element is the time it takes for half of its atoms to decay into something else.


The purpose of this chapter is to explain the process of radioactive decay and its relationship to the concept of half-life. Remember that a radionuclide represents an element with a particular combination of protons and neutrons nucleons in the nucleus of the atom. A radionuclide has an unstable combination of nucleons and emits radiation in the process of regaining stability. Reaching stability involves the process of radioactive decay.

A decay, also known as a disintegration of a radioactive nuclide, entails a change from an unstable combination of neutrons and protons in the nucleus to a stable or more stable combination. The type of decay determines whether the ratio of neutrons to protons will increase or decrease to reach a more stable configuration.

benefits of uranium what are 2 benefits of using carbon in dating the age of objects dating. Uranium uranium dating, method of age determination that makes use of the radioactive decay of uranium to uranium; the method can be.

See this page in: Hungarian , Russian , Spanish People who ask about carbon 14C dating usually want to know about the radiometric [1] dating methods that are claimed to give millions and billions of years—carbon dating can only give thousands of years. People wonder how millions of years could be squeezed into the biblical account of history.

Clearly, such huge time periods cannot be fitted into the Bible without compromising what the Bible says about the goodness of God and the origin of sin, death and suffering —the reason Jesus came into the world See Six Days? Christians , by definition, take the statements of Jesus Christ seriously. This only makes sense with a time-line beginning with the creation week thousands of years ago.

It makes no sense at all if man appeared at the end of billions of years. We will deal with carbon dating first and then with the other dating methods. How the carbon clock works Carbon has unique properties that are essential for life on Earth.


Special beta-decay processes In addition to the above types of radioactivity, there is a special class of rare beta-decay processes that gives rise to heavy-particle emission. In these processes the beta decay partly goes to a high excited state of the daughter nucleus, and this state rapidly emits a heavy particle. One such process is beta-delayed neutron emission, which is exemplified by the following reaction: There is a small production of delayed neutron emitters following nuclear fission, and these radioactivities are especially important in providing a reasonable response time to allow control of nuclear fission reactors by mechanically moved control rods.

Uranium–lead dating was applied initially to uranium minerals, e.g. uraninite and pitchblende, but as these are rather restricted in occurrence it is more normal to use the mineral zircon, even though the uranium is present only in trace amounts.

How old are you? How old are your grandparents? Do you know how old Canada is? Or the pyramids in Egypt? Do you know how old Earth is? How do scientists even know how old the Earth is? Or how long ago dinosaurs existed? Scientists have many ways to discover how old rocks and fossils are. The oldest and most reliable method they use is called Uranium-lead U-Pb dating. Scientists use this method to date rocks that formed from between 1 million to 4. Scientists can use monazite, titanite, baddeleyite and zirconolite for uranium dating.

Radiometric or Absolute Rock Dating