Tephrochronology dating websites

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The free oxygen that makes up the bulk of the present atmosphere evolved over geologic time by two possible processes.

First, solar ultraviolet radiation (the short-wavelength component of sunlight) would have provided the energy needed to break up water vapour into hydrogen, which escaped into space, and free oxygen, which remained in the atmosphere.

This age has been obtained from the isotopic analysis of many meteorites as well as of soil and rock samples from the Moon by such dating methods as rubidium–strontium and uranium–lead.

Meanwhile, heavier liquids rich in iron, nickel, and perhaps sulfur separated out and sank under gravity, giving rise to the core at the centre of the growing planet; and the lightest volatile elements were able to rise and escape by outgassing, which may have been associated with surface volcanic activity, to form the secondary atmosphere and the oceans.This mineral is the oldest dated material on Earth.The rocks from which the zircons in the quartzites and conglomerates were derived have either disappeared or have not yet been found.It is known from direct observation that the surface of the basaltic lavas caused by the impact-induced melting of the lunar mantle.Many of these basalts have been analyzed isotopically and found to have crystallization ages of 3.9 to 4 billion years.

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