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Uranium-thorium dating
 
 
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Uranium-thorium dating, also called thorium-230 dating, uranium-series disequilibrium dating or uranium-series dating, is a radiometric dating
Radiometric dating

Radiometric dating is a technique used to date materials, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates....
 technique commonly used to determine the age of carbonate materials such as speleothem
Speleothem

A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone Cave#Types and formation....
 or coral
Coral

Corals are marine organisms from the class Anthozoa and exist as small sea anemone?like polyps, typically in colonies of many identical individuals....
. Unlike other commonly used radiometric dating
Radiometric dating

Radiometric dating is a technique used to date materials, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates....
 techniques such as rubidium-strontium
Rubidium-strontium dating

The rubidium-strontium dating method is a radiometric dating technique that geology use to determine the rock dating.Development of this process was aided by Fritz Strassmann, who later moved onto discovering nuclear fission with Otto Hahn and Lise Meitner....
 or uranium-lead
Uranium-lead dating

Uranium-lead is one of the oldest and most refined radiometric dating schemes, with a routine age range of about 1 million years to over 4.5 billion years, and with routine precisions in the 0.1-1 percent range....
 dating, the uranium-thorium technique does not measure accumulation of a stable end-member decay product
Decay product

In nuclear physics, a decay product, also known as a daughter product, daughter isotope or daughter nuclide, is a nuclide resulting from the radioactive decay of a parent isotope or precursor nuclide....
, instead calculating an age from the degree to which equilibrium
Secular equilibrium

In nuclear physics, secular equilibrium is a situation in which the quantity of a radioactive isotope remains constant because its production rate is equal to its decay rate....
 has been restored between the radioactive isotope
Isotope

Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass . Isotopes of an element have atomic nucleus with the same number of protons but different numbers of neutron....
 thorium
Thorium

Thorium is a chemical element with the symbol Th and atomic number 90. As a naturally occurring, slightly radioactive metal, it has been considered as an alternative nuclear fuel to uranium....
-230 and its radioactive parent uranium
Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
-234 within a sample.

Because uranium
Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
 is soluble to some extent in all natural
Nature

File:Jungle in Punjab.JPGNature, in the broadest sense, is equivalent to the natural world, physical universe, material world or material universe....
 water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
s, any material that precipitates or is grown from such waters also contains trace uranium, typically at levels of between a few parts per billion and few parts per million by weight.






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Uranium-thorium dating, also called thorium-230 dating, uranium-series disequilibrium dating or uranium-series dating, is a radiometric dating
Radiometric dating

Radiometric dating is a technique used to date materials, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates....
 technique commonly used to determine the age of carbonate materials such as speleothem
Speleothem

A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone Cave#Types and formation....
 or coral
Coral

Corals are marine organisms from the class Anthozoa and exist as small sea anemone?like polyps, typically in colonies of many identical individuals....
. Unlike other commonly used radiometric dating
Radiometric dating

Radiometric dating is a technique used to date materials, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates....
 techniques such as rubidium-strontium
Rubidium-strontium dating

The rubidium-strontium dating method is a radiometric dating technique that geology use to determine the rock dating.Development of this process was aided by Fritz Strassmann, who later moved onto discovering nuclear fission with Otto Hahn and Lise Meitner....
 or uranium-lead
Uranium-lead dating

Uranium-lead is one of the oldest and most refined radiometric dating schemes, with a routine age range of about 1 million years to over 4.5 billion years, and with routine precisions in the 0.1-1 percent range....
 dating, the uranium-thorium technique does not measure accumulation of a stable end-member decay product
Decay product

In nuclear physics, a decay product, also known as a daughter product, daughter isotope or daughter nuclide, is a nuclide resulting from the radioactive decay of a parent isotope or precursor nuclide....
, instead calculating an age from the degree to which equilibrium
Secular equilibrium

In nuclear physics, secular equilibrium is a situation in which the quantity of a radioactive isotope remains constant because its production rate is equal to its decay rate....
 has been restored between the radioactive isotope
Isotope

Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass . Isotopes of an element have atomic nucleus with the same number of protons but different numbers of neutron....
 thorium
Thorium

Thorium is a chemical element with the symbol Th and atomic number 90. As a naturally occurring, slightly radioactive metal, it has been considered as an alternative nuclear fuel to uranium....
-230 and its radioactive parent uranium
Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
-234 within a sample.

Because uranium
Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
 is soluble to some extent in all natural
Nature

File:Jungle in Punjab.JPGNature, in the broadest sense, is equivalent to the natural world, physical universe, material world or material universe....
 water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
s, any material that precipitates or is grown from such waters also contains trace uranium, typically at levels of between a few parts per billion and few parts per million by weight. In contrast, thorium
Thorium

Thorium is a chemical element with the symbol Th and atomic number 90. As a naturally occurring, slightly radioactive metal, it has been considered as an alternative nuclear fuel to uranium....
 is not soluble in natural waters under conditions found at or near the surface of the earth and so materials grown in or from these waters do not usually contain thorium. As time passes after the formation of such a material, the uranium-234 in the sample decays to thorium-230, with a half-life
Half-life

The half-life of a quantity whose value decreases with time is the interval required for the quantity to decay to half of its initial value. The concept originated in describing how long it takes atoms to undergo radioactive decay but also applies in a wide variety of other situations....
 of 245,000 years. The thorium-230 is itself radioactive with a half-life
Half-life

The half-life of a quantity whose value decreases with time is the interval required for the quantity to decay to half of its initial value. The concept originated in describing how long it takes atoms to undergo radioactive decay but also applies in a wide variety of other situations....
 of 75,000 years and so instead of accumulating indefinitely (as for instance is the case for the uranium-lead
Uranium-lead dating

Uranium-lead is one of the oldest and most refined radiometric dating schemes, with a routine age range of about 1 million years to over 4.5 billion years, and with routine precisions in the 0.1-1 percent range....
 system) it instead approaches secular equilibrium
Secular equilibrium

In nuclear physics, secular equilibrium is a situation in which the quantity of a radioactive isotope remains constant because its production rate is equal to its decay rate....
 with its parent isotope. At equilibrium, the number of thorium-230 decays per year within a sample is equal to the number of uranium-234 decays per year in the same sample.

Uranium-thorium dating has an upper age limit of somewhat over 500,000 years, defined by the half-life of thorium-230, the accuracy with which we can measure the thorium-230/uranium-234 ratio in a sample, and the precision
Precision

Precision has the following meanings:Concepts* Accuracy and precision, measurement deviation from true value and its scatter* arithmetic precision, the number of digits from which a value is expressed...
 to which we know the half-lives of thorium-230 and uranium-234. Note that to calculate an age using this technique the ratio of uranium-234 to its parent isotope uranium-238 must also be measured.