Dating the life of the earth

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In summary: U-Pb dating because it is very clear, and it does not form any other minerals that would obscure the uranium-lead ratio.In summary, the uranium-lead dating is based on how much lead is present in combination with uranium. Lead being the final element after the uranium decay. The dating is based on the ratio of lead that was present in combination with uranium. lead being the final element after the uranium decay. The process of crystallization has a purifying effect and only specific materials are suitable for uranium-lead dating. Zircon is a crystal that results in the separation of uranium and lead, and Cleonisant quartz is another material that can be used for U
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Impulse2
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I was looking at a program referring to dating the life of the Earth and I`m puzzled on a bit that I`m sure must be obvious to geologists. The dating was based on the ratio of lead that was present in combination with uranium. Lead being the final element after the uranium decay.
It was this varying ratio from locality that enabled the dating of the area. But doesn`t all the uranium on the Earth decay at the same rate and would not all have the same Ur/Pb ratio? Why would the decay, as was stated, of rocks at the bottom of the Grand Canyon be a billion or so years different from those on the surface as determined by the Ur/Pb ratio?
 
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Hi Impulse2! :smile:

These particular rocks are created with uranium and no lead.

Yes, the uranium in the rock has been decaying "for ever", but the lead produced has just disapppeared until the uranium got into the rock.

Only then is the lead trapped (and so is the uranium, of course) where we can find and measure it. :wink:

(for more details, see http://en.wikipedia.org/wiki/Uranium-lead_dating" [Broken])
 
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Impulse2 said:
Why would the decay, as was stated, of rocks at the bottom of the Grand Canyon be a billion or so years different from those on the surface as determined by the Ur/Pb ratio?

I started reading the link to the wikipedia article mentioned by tiny-tim.

When molten material cools very slowly there is a gradual process of crystallization. The process of crystallization has a purifying effect.

In fact, crystallization is how sugar that is harvested form beets or sugar canes is purified. The unpure suger is dissolved in hot water, and then the temperature of the solution is decreased very slowly. The sugar starts to crystallize. A crystal with no inclusions of molecules with a different shape is the lowest energy configuration. So when the crystallization proceeds slow enough non-sugar molecules that do not have a snug fit in the crystal do not find a place, and you end up with purified sugar crystals. (Sugar that is purified in this way is often branded as 'crystal sugar'.)

For Uranium-Lead dating only specific materials are suitable: they must be crystals that formed during very slow cooling of molten material, and they must be materials in which Uranium is readily incorporated in the crystal structure, while Lead is not incorporated.

Such materials do exist, and the wikipedia article mentions that usually socalled Zircon crystals are picked. Zircon is Zirconium Silicate.

The formation of Zircon crystals results in separation of Uranium from Lead, and that way the "clock" is reset.

Cleonis
 

What is radiometric dating and how does it work?

Radiometric dating is a method used by scientists to determine the age of rocks and other materials on Earth. It works by measuring the amount of radioactive elements in a sample and comparing it to the amount of decay products. The rate of decay of these elements is constant, making it possible to calculate the age of the sample.

What is the oldest age that has been determined for the Earth using radiometric dating?

The oldest age determined for the Earth using radiometric dating is 4.54 billion years. This age was obtained by dating meteorites, which are believed to have formed at the same time as the Earth.

What are the limitations of radiometric dating?

While radiometric dating is a reliable method for determining the age of rocks and other materials, it does have its limitations. One limitation is that it can only be used on materials that contain radioactive elements. Additionally, the accuracy of the dating can be affected by external factors such as contamination or changes in the rate of decay.

How does radiometric dating support the theory of evolution?

Radiometric dating is one of the main pieces of evidence used to support the theory of evolution. By dating different layers of rock and fossils found in them, scientists are able to create a timeline of Earth's history and the evolution of different species over time.

What other methods are used to determine the age of the Earth?

In addition to radiometric dating, scientists also use other methods such as studying the Earth's magnetic field, analyzing the composition of rocks, and examining the fossil record to determine the age of the Earth. Each method has its own strengths and limitations, and using multiple methods can provide a more accurate estimate of the Earth's age.

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