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Unformatted text preview: he Precambrian, there were essentially no fossils, so not a lot of detail to the geological time scale before the Cambrian. Relative age dating using fossils Fossils can be used to correlate rocks from place to place Absolute Time Get absolute dates from radiometric dating. Radiometric dating is based on the process of radioactive decay. Radioactive decay occurs when a neutron decays into a proton and an electron. The rate at which this decay occurs is measure in half-lives... Which parent-daughter pair is used for dating the rock depends on its minerals, age. Can now add dates to the Geologic Time scale. The oldest date on this time scale is 2.5 billion years. But how old is the earth? About 4.6 billion years old Oldest continental rocks: 4 billion years old Oldest oceanic rocks: a mere 200 million years old We know the age of the earth from radiometric dating of stoney meteorites (see below). These meteorites have never been heated above 100 degrees, so have never been part of a planet (other types of meteorites are bits of Mars, for instance). Evolution of the Sola...
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- Fall '07