Absolut dating

Posted by / 27-Aug-2014 20:03

Absolut dating

He believed the Earth started off as a molten mass and subsequently transformed to a hot solid mass during cooling. Instead, Chamberlain proposed a model of cold accretion for the Earth.

That is, the earth accreted from small, cold chunks of material and then heated up at a later time.

However, we can predict what fraction of the parent atoms will decay over a certain amount of time because each radioactive isotope has a constant rate of decay (unaffected by temperature, pressure, or chemical state).

For example, isotopes with very long half lives are no good for dating rocks younger than about 100 million years.

Buffon's Iron Sphere Experiments- On the basis of iron sphere cooling experiments, Frenchman Georges de Buffon estimated that the Earth would have needed 75,000 years to cool to its present temperature.

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.

Mountains, erosion, and variations in climate were considered to be punishment for the sins committed by humanity.

Although development of radiometric methods led to the first breakthroughs in establishing an absolute time scale, other absolute methods have limited applications.

Chief among these are dendochronology, varve analysis, hydration dating, and TL dating.

Dendochronologists can use this index to date accurately events and climatic conditions of the past 3000-4000 years.

Varve Analysis This technique was developed by Swedish scientists in the early 20th century.

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A varve is a sedimentary bed, or sequence of beds, deposited in a body of still water within a year’s time.

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