The estimation of age of most ancient geological formations is done using which of the following methods?

Options :
  1. Potassium - argon method
  2. Ra - Si method
  3. C14 method
  4. Uranium - lead method
Answer and Explanation :-

Answer: Option 3


The Carbon-14 dating method, also called Radiocarbon dating method, is a method of age determination that depends upon the decay to nitrogen of Radiocarbon (Carbon-14). The carbon-14 method was developed by the American physicist Willard F. Libby in 1946-47. It has proved to be a versatile technique of dating fossils and archaeological specimens from 500 to 50,000 years old. The method is widely used by Pleistocene geologists, anthropologists, archaeologists, and investigators in related fields. Radiocarbon dating is based on the fact that the interaction of cosmic rays from outer space with nitrogen atoms in the atmosphere produces an unstable isotope of carbon, namely radiocarbon. Since it is chemically indistinguishable from the stable isotopes of carbon (carbon-12 and carbon-13), radiocarbon is taken by plants during photosynthesis and then ingested by animals regularly throughout their lifetimes. When a plant or animal organism dies, however, the exchange of radiocarbon from the atmosphere and the biosphere stops, and the amount of radiocarbon gradually decreases, with a half-life of approximately 5730 years. Because of this relatively short half-life, radiocarbon is useful for dating items of a relatively recent vintage, as far back as roughly 50,000 years before the present epoch. Radiocarbon dating cannot be used for older specimens, because so little carbon-14 remains in samples that it cannot be reliably measured. For dating older specimens other radioactive dating methods are used. They include potassium-argon dating, that's useful for rocks over 100,000 years old. There's also uranium-lead dating, which has an age range of 1-4.5 million years old. It can be used for such long time spans because the half-life of uranium turning into lead is billions of years, in the order of the age of the Earth at 4.5 billion years.

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By: Dr Ashish On: Jun/18/2014

Nice answers and quite useful

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