Stratigraphy

This episode, the seventh in our Introduction to Geology course, focuses on stratigraphy, the study of rock layers. Building upon our knowledge of geology, Earth, geologists, rocks, minerals, and the geological time scale, we will explore how stratigraphy helps us understand Earth's history. We will examine the principles of stratigraphy, including superposition, original horizontality, and cross-cutting relationships, and learn how geologists use these principles to interpret the sequence of events that shaped our planet. This episode provides a foundation for understanding how Earth's history is recorded in its rock layers.

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.

Which principle states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom?

  1. Principle of original horizontality
  2. Principle of superposition
  3. Principle of cross-cutting relationships
  4. Principle of uniformitarianism

What is the study of rock layers called?

  1. Mineralogy
  2. Petrology
  3. Stratigraphy
  4. Paleontology

If a fault cuts across several rock layers, which is younger?

  1. The rock layers
  2. The fault
  3. They are the same age
  4. It depends on the type of rock

What can fossils help stratigraphers determine?

  1. The absolute age of rocks
  2. The relative ages of rock layers
  3. The composition of rocks
  4. The temperature at which rocks formed

Which of the following principles is NOT a fundamental principle of stratigraphy?

  1. Principle of superposition
  2. Principle of original horizontality
  3. Principle of cross-cutting relationships
  4. Principle of uniformitarianism

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