Summary
Imagine Earth’s history as a giant book, with rocks and fossils as its pages. How do scientists read this book without page numbers? They use two main methods: relative time and absolute time. These techniques help us figure out which “chapters” came first and how long ago they were written. In this lesson, you’ll learn how geologists unlock these clues and practice the skills needed to date rocks and fossils—like becoming a detective of Earth’s past!
Miocene fossils on display at the Denver Museum of Nature and Science in Denver, CO
Fossil ages range from 7-million years old to 13-million years old.
Learning Outcomes
- Differentiate between relative dating and absolute dating by defining each method and explaining their key differences.
- Describe the concept of stratigraphy and analyze its significance in determining relative ages of rock layers.
- Identify and explain the fundamental principles of relative dating (e.g., superposition, original horizontality, cross-cutting relationships).
- Apply relative dating principles to interpret the chronological sequence of events in given stratigraphic column examples.
- Explain the process of radioactive decay and evaluate its role in determining the absolute age of rocks and fossils.
- List and describe common radioactive isotopes used for absolute age determination and their geological applications.
- Define and illustrate the concept of half-life and its significance in radiometric dating.
- Calculate the approximate absolute age of rocks and fossils using isotope data and half-life values through worked examples.
- Integrate and apply principles of relative and absolute dating to interpret subsurface geology and assess potential oil and gas reservoir locations.
Image Credits
- Fossils: Sabrina Ewald