Methods of dating fossils

• What are the two main methods for dating fossils?

  Relative dating and radiometric dating
• What is relative dating?

  • Uses fossil study and rock layers
  • Compares two or more things to establish relative age
  • Determines if one fossil is older or younger than another
• How do scientists determine the relative age of fossils found at different depths?

  They assume that the fossil found at greater depth is older
• What is the Law of Similar Fossil?

  It is used to date hominid fossils in South Africa
• What is stratigraphic dating?


  • A method of relative dating
  • Uses the depth of rock layers to determine relative age
  • Deeper layers are generally older than those closer to the surface
• What factors can affect the accuracy of stratigraphic dating?

  Volcanic activity, earthquakes, and unpredictable rock formation
• What does fluorine analysis compare to determine the relative age of bones?

  The fluorine content of two or more fossilized bones
• What are the limitations of fluorine analysis?

  • Can only determine relative ages of bones from the same site
  • Does not provide exact ages
• What is the approximate age of the Earth determined by scientists?

  Approximately 4.6 billion years old
• How does radiometric dating work?

  • Measures radioactive decay of isotopes in rocks
  • Provides a reliable indicator of age
  • More accurate than relative dating
• What is potassium-argon dating used for?

  To measure the decay of potassium-40 to argon-40
• What is the half-life in potassium-argon dating?

  The rate at which potassium-40 decays into argon-40
• What type of material can potassium-argon dating be used on?

  Inorganic material
• What is carbon-14 dating used for?

  To date both organic and inorganic material
• Why is carbon-14 dating more appropriate for later materials?

  Because carbon-14 decays at a significantly faster rate than potassium-40
• What happens to the accuracy of carbon-14 dating on samples older than 40,000 years?

  Its accuracy drops significantly
• How do scientists combine relative and radiometric dating?

  • To find the age of a fossil
  • By discovering relative and specific ages of different specimens
  • To understand the development of organisms through geological periods
• What is inference in the context of paleontology?

  Using existing knowledge or data to interpret fossil evidence
• What conclusion did paleontologists draw about Archaeopteryx?

  That it could have been the first bird
• What evidence led scientists to conclude that Archaeopteryx could have been birds?

  Impressions of feathers found in the rock near the fossil