Question

Why is radiocarbon dating not good for material more than 30,000 years old?
1. Because all animals emitted radiocarbon before that time
2. Because radiocarbon was not present anywhere before that time
3. Because the amount of C14 becomes almost immeasurably small in 30,000 years
4. Because carbon extraction was not known before 30,000 years

Answer 1

Correct Answer - Option 3 : Because the amount of C14 becomes almost immeasurably small in 30,000 years

Option 3 is not correct.

• The group theorizes that large errors in carbon dating result from fluctuations in the amount of carbon 14 in the air.
  • Carbon 14 is thought to be mainly a product of the bombardment of the atmosphere by cosmic rays, so cosmic ray intensity would affect the amount of carbon 14 in the environment at any given time.
  • 30,000-Year Limit The Lamont-Doherty group says uranium-thorium dating not only is more precise than carbon dating in some cases but also can be used to date much older objects.
  • Carbon dating is unreliable for objects older than about 30,000 years, but uranium-thorium dating may be possible for objects up to half a million years old, Dr Zindler said.
    • The method is less suitable, however, for land animals and plants than for marine organisms, because uranium is plentiful in seawater but less so in most soils.
• Hence option 3 is correct.

• Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.
• The method was developed in the late 1940s at the University of Chicago by Willard Libby, who received the Nobel Prize in Chemistry for his work in 1960.
  • It is based on the fact that radiocarbon (14 C) is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen.