About This Chapter
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
|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.|
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.
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.
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.
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!
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.
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.
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!
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.
Earning College Credit
Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.
To learn more, visit our Earning Credit Page
Transferring credit to the school of your choice
Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.
Other chapters within the Earth Science 101: Earth Science course
- Earth Science Basics
- Characteristics of Matter
- Earth's Spheres and Internal Structure
- Plate Tectonics
- Minerals and Rocks
- Igneous Rocks
- Volcanic Landforms
- Weathering and Erosion
- Sedimentary Rocks: A Deeper Look
- Metamorphic Rocks: A Deeper Look
- Rock Deformation and Mountain Building
- Water Balance on Earth
- Running Water
- Ground Water
- Coastal Hazards
- Earth's Atmosphere
- Weather, Air Masses & Storms
- Earth History
- Energy Resources
- Studying for Earth Science 101