Radioactivity Dating

1
Radioactivity Dating

• Measuring the radioisotope decay in rock sediment
• Each radioisotope has an characteristic
  half-life
• Tritium (3H)
• 12.3 years
• Carbon-14 (14C)
• 5,700 years
• the ratio of 14C and 12C (non-radioactive) is
  always the same as is in the environment since
  carbon is always exchanged between each. As soon
  as an organism dies the ratio decreases. By
  measuring the 14C we can tell when the organism
  died. This measurement is good up to about 30,000
  years
• Potassium-40 (40K)
• 1.3 billion years
• has been used to date most of the ancient events
  in the evolution of life
• Uranium-238 (238U)
• 10 billion years