Radiometric dating of ordovician period

Still older are zircon crystals found in sedimentary rock from Western Australia. They are not intact original crust material either.The rock from which they originated eroded, and the individual particles became part of the later sedimentary rock that was sampled.However, he neglected to take into account the fact that some heat from the earth's core is regularly conducted to the crust.He also was unaware of the fact that intense heat is still being produced inside the earth by radioactive decay.If that were true, it would be possible to measure the thickness of all known fossil bearing strata and multiply it by a presumed constant evolution rate to determine the total amount of time passed.The English geologist Still another flawed method for estimating the age of the earth was devised by Lord Kelvin (William Thomson) in 1862.In 1691, the British astronomer and mathematician proposed that if the original oceans were fresh water, one could calculate the minimum age of the earth by dividing the total amount of salt now present in the oceans by the amount added each year from the world's rivers and streams.Those water sources bring with them mineral salts eroded from the land.

The oldest still intact rock found so far is from the eastern shore of Canada's Hudson Bay.

However, before the 1960's, scholars in many cultures tried to estimate the age of the earth and of life.

, an ancient Egyptian historian, listed all of the dynasties of pharaohs and gods that reigned down to his time (3rd century B. This made the earth about 38,000 years old (from our time). D., accepted the Judeo-Christian Old Testament as being literally true and subsequently determined the age of the earth by counting biblical generations and adding their time to modern recorded history. With the rapid growth of European scientific knowledge, largely beginning in the late 17th century A.

By the mid 19th century, some geologists were estimating the amount of time for the successive changes in animal species found as fossils in the sedimentary rock layers identified by William Smith.

It was wrongly assumed that species evolve at a steady, measurable rate.

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