Dating radioactive elements
Lyell's extreme form of uniformitarianism would have required a perfect balance between heat production and heat loss.Kelvin argued that this was physically impossible (the concept is akin to a perpetual motion machine).Strata Thickness- In the late 1800s, a British geologist estimated that 75 million years has lapsed since the beginning of the Cambrian.This estimate was based upon the maximum known thickness of strata (from Cambrian to present) divided by the average rate of sedimentation in modern environments. Joly used the salinity of ocean water to determine the age of the earth.Chronological Analysis of the Scriptures- Literal interpretation of the scriptures led some people to conclude that the Earth was created approximately 6,000 years old.In fact, Archbishop Usher of Ireland calculated that the Earth was created at 9 AM on It was believed that prior to the Great Flood, Earths surface was flat and its climate was mild.Carbon-14 has a relatively short half life of 5,730 years. Beyond 60,000 - 80,000 years, there is too little Carbon-14 left in the sample and this technique cannot be used.
Beyond 100,000,000 years, the density of the tracks becomes so great (saturated) that they cannot be counted reliably.The quantitative approach is admirable, but Buffon's assumptions are flawed. Silicate minerals have lower heat conductivity than steels and are better insulators leading to slower cooling rates.Second, the calculations did not incorporate the heating effects of radioactive decay.When an organism dies it ceases to replenish carbon in its tissues and the decay of carbon 14 to nitrogen 14 changes the ratio of carbon 12 to carbon 14.Experts can compare the ratio of carbon 12 to carbon 14 in dead material to the ratio when the organism was alive to estimate the date of its death.
Search for dating radioactive elements:
For example, isotopes with very long half lives are no good for dating rocks younger than about 100 million years.