Facts about geologic dating
In 1986 they further discovered that one zircon in a conglomerate only 60 km (about 37 miles) away was 4.276 billion years old; 16 other grains were determined to be the same age or slightly younger.
In 2014 American geochemist John Valley and colleagues discharged lead atoms at one of the zircon crystals discovered in western Australia’s Jack Hills and discovered that the crystals are more than 4.4 billion years old.
Models developed from the comparison of lead isotopes in meteorites and the decay of hafnium-182 to tungsten-182 in Earth’s mantle, however, suggest that approximately 100 million years elapsed between the beginning of the solar system and the conclusion of the accretion process that formed Earth.
These models place Earth’s age at approximately 4.5 billion years old.
It is known from direct observation that the surface of the basaltic lavas caused by the impact-induced melting of the lunar mantle.
The increase in temperature became sufficient to heat the entire planet.Carbon monoxide, carbon dioxide, water vapour, and methane predominated; however, free oxygen could not have been present, since even modern volcanic gases contain no oxygen.It is therefore assumed that the secondary atmosphere during the Archean Eon (4 billion to 2.5 billion years ago) was anoxygenic.Such intense bombardment would have covered most of Earth’s surface, with the impacts causing considerable destruction of the terrestrial crust up to 4 billion years ago.An exciting discovery was made in 1983 by zircon grains that were 4.18 billion years old.