Radioactive dating age of earth

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Therefore, their ages indicate when they were formed.Because all parts of the solar system are thought to have formed at the same time (based on the solar nebula theory), the Earth must be the same age as the moon and meteorites--that is, about 4.6 billion years old.Recently, rocks over 3.96 billion years old have been dated from northern Canada, Wyoming, and China.The ages of these oldest rocks still don't tell us how old the Earth is, but they do establish a minimum age.One way to think about the closed system of the crystal is to compare it to an hourglass.The grains of sand in the top half of the hourglass are the radioactive parents, and those falling to the bottom are the stable daughters.The oldest rocks and soils from the moon are about the same age--4.6 billion years old.Scientists assume that meteorites and moon rocks were not subjected to the extensive alteration that Earth rocks have undergone.

Radiometric dating shows that almost all meteorites are between 4.5 and 4.7 billion years old.Radiometric dating works best on igneous rocks, which are formed from the cooling of molten rock, or magma.As magma cools, radioactive parent isotopes are separated from previously formed daughter isotopes by the crystallization process.Another line of evidence is based on the present-day abundances of the various isotopes of lead found in the Earth's crust. Three of these isotopes (lead 206, 207, 208) result from radioactive decay of isotopes of thorium and uranium.The fourth, lead 204, is not the result of radioactive decay.

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