How do geologists know how to determine half-lives and ...

[Yolanda]

How do geologists know how to determine half-lives and decay-rates?
 
  What will be an ideal response?

Question 2

Metamorphism usually ________ the radioactive-isotope clock.
 
  A) retains
  B) preserves
  C) maintains
  D) resets

[kiamars2010]

Answer to Question 1

Answer: Radioactive-decay rates are measured in the laboratory by detecting the energy released by each decay event. Decay rates are expressed as the number of decays per unit of time per gram of parent isotope. Decay rates measured in different laboratories are the same within the uncertainty of the measurement. International committees establish the universally used decay rates based on the most reliable and upto-date laboratory values. Laboratory experiments show that decay rates are unaffected by changes in temperature, pressure, variations in gravitational field, or different magnetic fields.

Answer to Question 2

Answer: D