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Ch 2: Geologic Time

About This Chapter

Watch online video lessons to learn about catastrophism, radioactive dating, fossil preservation and more. Each lesson is accompanied by a short multiple-choice quiz you can use to check your understanding of these geologic time concepts.

Geologic Time - Chapter Summary and Learning Objectives

Have you ever wondered how scientists, archeologists and others date things to a time in the past? For example, how do they know when the dinosaurs lived or what time period the mummy they just found was from? Well, as people have studied and researched the past, the knowledge of geological time periods evolved, which allows items to be dated back to various time periods. In this chapter, we take a look at geological time. You'll learn the names of different eons, eras, periods and epochs that are used to refer to when something occurred or when in time a found item came from. Lessons will take a look at evolution and dating methods, too. You will get to understand more about things like:

  • The subdivisions of the geological time scale
  • Catastrophism and uniformitarianism
  • Relative dating
  • Radioactive dating
  • Fossil preservation

VideoObjective
Geological Time Scale: Major Eons, Eras, Periods and Epochs Examine the geological time scale and its principle subdivisions.
Theories of Geological Evolution: Catastrophism vs. Uniformitarianism Compare and contrast the theories of geological evolution.
Methods of Geological Dating: Numerical and Relative Dating Explore the differences between numerical dating and relative dating and how they are used by geologists to study earth's history.
What is Relative Dating? - Law of Superposition, Principles of Original Horizontality & Cross-Cutting Relationships Discover these concepts related to relative dating and see how inclusions and unconformities are used to establish relative dates.
Principles of Radioactive Dating & The Significance of Half-Life Take a look at the common types of radioactive decay, the relationship between parent and daughter isotopes and the significance of half-life.
Radioactive Dating: Methods, Uses and Limits of Radioactive Decay as a Dating Tool Learn how radioactive decay is used to determine numerical age, along with learning the major methods of radioactive dating and the uses and limits of each.
Conditions of Fossil Preservation: Rapid Burial, Hard Parts & Temperature Study the conditions favoring preservation, including rapid burial, hard parts and temperature.
Relative Dating with Fossils: Index Fossils as Indicators of Time Find out about the principle of fossil succession and the use of index fossils as indicators of time.

8 Lessons in Chapter 2: Geologic Time
Geologic Time Scale: Major Eons, Eras, Periods and Epochs

1. Geologic Time Scale: Major Eons, Eras, Periods and Epochs

The geologic time scale is an essential tool for understanding the history of Earth and the evolution of life. In this lesson, explore the principal eons, eras, periods, and epochs that help us track major events in geologic history.

Theories of Geological Evolution: Catastrophism vs Uniformitarianism

2. Theories of Geological Evolution: Catastrophism vs Uniformitarianism

Geologists haven't always agreed about the history of our planet. They have debated between catastrophism and uniformitarianism over the last few hundred years! Learn about the two main theories of geologic evolution and how scientists came to resolve the dispute.

Methods of Geological Dating: Numerical and Relative Dating

3. Methods of Geological Dating: Numerical and Relative Dating

Learn how scientists determine the ages of rocks and fossils. We'll explore both relative and numerical dating on our quest to understand the process of geological dating. Along the way, we'll learn how stratigraphic succession and radioactive decay contribute to the work of paleontologists.

What is Relative Dating? - Law of Superposition, Principles of Original Horizontality & Cross-Cutting Relationships

4. What is Relative Dating? - Law of Superposition, Principles of Original Horizontality & Cross-Cutting Relationships

Discover how geologists study the layers in sedimentary rock to establish relative age. Learn how inclusions and unconformities can tell us stories about the geologic past. We'll even visit the Grand Canyon to solve the mystery of the Great Unconformity!

Principles of Radiometric Dating

5. Principles of Radiometric Dating

Radiometric dating is a method used to determine the age of rocks and other materials based on the rate of radioactive decay. Learn about three common types of radioactive decay: alpha decay, beta decay and gamma decay.

Radiometric Dating: Methods, Uses & the Significance of Half-Life

6. Radiometric Dating: Methods, Uses & the Significance of Half-Life

Radiometric dating is used to estimate the age of rocks and other objects based on the fixed decay rate of radioactive isotopes. Learn about half-life and how it is used in different dating methods, such as uranium-lead dating and radiocarbon dating, in this video lesson.

Conditions of Fossil Preservation: Rapid Burial, Hard Parts & the Elements

7. Conditions of Fossil Preservation: Rapid Burial, Hard Parts & the Elements

Learn how fossils are formed and how varying conditions affect the preservation of organisms. What is the best way for a dinosaur to become fossilized? Find out here!

Relative Dating with Fossils: Index Fossils as Indicators of Time

8. Relative Dating with Fossils: Index Fossils as Indicators of Time

You may already know how to date a fossil with a rock. But did you know that we can also date a rock with a fossil? Watch this video to find out how we use index fossils to establish the relative ages of rocks.

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