Determinations based on comparisons of ages of earth minerals and rocks give two different values of the Rb half-life and decay constant to the values using determinations based on comparison of ages of meteorites and lunar rocks.
Yet the most recent direct counting and in-growth experimental determinations only agree with the most recent determinations based on comparison of the Rb-Sr ages of earth minerals and rocks with their U-Pb “gold standard” ages.
Because rubidium is concentrated in crustal rocks, the continents have a much higher abundance of the daughter isotope strontium-87 compared with the stable isotopes.
This relative abundance is expressed as the Sr ratio, where strontium-86 is chosen to represent the stable isotopes strontium-88, strontium-86, and strontium-84, which occur in constant proportions in natural materials.
he question of the ages of the Earth and its rock formations and features has fascinated philosophers, theologians, and scientists for centuries, primarily because the answers put our lives in temporal perspective.
Until the 18th century, this question was principally in the hands of theologians, who based their calculations on biblical chronology.
James Joly calculated that the Earth’s age was 89 million years on the basis of the time required for salt to accumulate in the oceans.Both the scientific community and the general public around the world (except perhaps in the USA) thus remain convinced of the earth’s claimed great antiquity.The 1997–2005 RATE (arth) project successfully made progress in documenting some of the pitfalls in the radioisotope dating methods, and especially in demonstrating that radioisotope decay rates may not have always been constant at today’s measured rates (Vardiman, Snelling, and Chaffin 2000, 2005).In contrast, Earth’s most abundant lava rocks, which represent the mantle and make up the major oceanic ridges, have values between 0.703 and 0.705.This difference may appear small, but, considering that modern instruments can make the determination to a few parts in 70,000, it is quite significant.