Half life radiometric dating element
He calculated the modern rate of salt delivery to the oceans, and suggested that the present salinity of ocean water would take at least 100 million years to develop.
In the 1860's, English physicist Lord Kelvin disagreed with Charles Lyells proposition that the earth behaves in a uniform, unchanging manner.
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.
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.
Thus they probably formed at a depth of 100–200 km.
Geologists believe that the ones we find must have been transported supersonically to the surface, in extremely violent eruptions through volcanic pipes.
Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.
Mountains have been built and eroded, continents and oceans have moved great distances, and the Earth has fluctuated from being extremely cold and almost completely covered with ice to being very warm and ice-free.