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Geology & Earth Sciences vocabulary · Geologic Time & Fossils

Half-life

Meaning in geology & earth sciences, with examples

/ˈhæf laɪf/nounCommon term

In geology & earth sciences, half-life means: The time it takes for half of the atoms of a radioactive isotope in a sample to decay. Each isotope has its own fixed half-life.

In Turkish: yarı ömür, yarılanma süresi

How it is used

The basis of radiometric dating. Half-lives range from fractions of a second to billions of years: carbon-14 has a half-life of about 5,730 years and uranium-238 about 4.5 billion years. Usually written with a hyphen; the plural is half-lives.

Example sentences

  1. After one half-life, half of the original isotope remains; after two, only a quarter is left.

  2. Uranium-238 has a half-life of about 4.5 billion years.

Common collocations

  • a half-life of
  • a short half-life
  • a long half-life
  • radioactive half-life
  • radiometric datingA method of finding the age of rocks and minerals by measuring how much of a radioactive element has decayed into its products, using the known rate of decay.
  • geologic time scaleThe system that divides the Earth's roughly 4.6-billion-year history into named units such as eons, eras, periods and epochs, based on rocks and fossils.
  • index fossilA fossil of a species that lived for only a short time but was widespread and easy to identify, so it is used to date rock layers and match them between areas.

This word in other fields

The same English word can have a different meaning in another field:

More terms: Geologic Time & Fossils

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