Geological time scale

This episode, "Geological Time Scale," introduces the vast expanse of Earth's history and the framework geologists use to organize it. Building upon our understanding of geology, Earth, rocks, and minerals, we'll explore how scientists have pieced together the story of our planet over billions of years. We'll learn about the major divisions of geological time – eons, eras, periods, and epochs – and the key events that define them, such as mass extinctions and major evolutionary changes. We'll also discuss the methods used to date rocks and fossils, providing a sense of the immense timescale involved in geological processes.

Check your understanding

These are the same multiple-choice questions you will see in the Quiz section after you listen to the episode. Use them here to preview or review the answers.

What is the approximate age of the Earth?

  1. 6,000 years.
  2. 4.54 million years.
  3. 4.54 billion years.
  4. 13.8 billion years.
  5. 100 million years

What is the largest division of the geological time scale?

  1. Period.
  2. Epoch.
  3. Era.
  4. Eon.
  5. Age.

Which eon are we currently in?

  1. Hadean.
  2. Archean.
  3. Proterozoic.
  4. Phanerozoic.
  5. Precambrian

What is the principle that states that in undisturbed rock layers, the oldest layers are at the bottom?

  1. Law of Superposition.
  2. Principle of Uniformitarianism.
  3. Law of Original Horizontality.
  4. Principle of Cross-Cutting Relationships.
  5. Law of Faunal Succession

Which dating method relies on the decay of radioactive isotopes?

  1. Relative dating.
  2. Radiometric dating.
  3. Stratigraphy.
  4. Fossil correlation.
  5. Lithostratigraphy

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