Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgments
- PART ONE THE ASTRONOMICAL PLANET: EARTH'S PLACE IN THE COSMOS
- PART TWO THE MEASURABLE PLANET: TOOLS TO DISCERN THE HISTORY OF EARTH AND THE PLANETS
- 5 Determination of Cosmic and Terrestrial Ages
- 6 Other Uses of Isotopes for Earth History
- 7 Relative Age Dating of Cosmic and Terrestrial Events: The Cratering Record
- 8 Relative Age Dating of Terrestrial Events: Geologic Layering and Geologic Time
- 9 Plate Tectonics: An Introduction to the Process
- PART THREE THE HISTORICAL PLANET: EARTH AND SOLAR SYSTEM THROUGH TIME
- PART FOUR THE ONCE AND FUTURE PLANET
- Index
- Plate section
8 - Relative Age Dating of Terrestrial Events: Geologic Layering and Geologic Time
from PART TWO - THE MEASURABLE PLANET: TOOLS TO DISCERN THE HISTORY OF EARTH AND THE PLANETS
- Frontmatter
- Contents
- Preface
- Acknowledgments
- PART ONE THE ASTRONOMICAL PLANET: EARTH'S PLACE IN THE COSMOS
- PART TWO THE MEASURABLE PLANET: TOOLS TO DISCERN THE HISTORY OF EARTH AND THE PLANETS
- 5 Determination of Cosmic and Terrestrial Ages
- 6 Other Uses of Isotopes for Earth History
- 7 Relative Age Dating of Cosmic and Terrestrial Events: The Cratering Record
- 8 Relative Age Dating of Terrestrial Events: Geologic Layering and Geologic Time
- 9 Plate Tectonics: An Introduction to the Process
- PART THREE THE HISTORICAL PLANET: EARTH AND SOLAR SYSTEM THROUGH TIME
- PART FOUR THE ONCE AND FUTURE PLANET
- Index
- Plate section
Summary
INTRODUCTION
Prior to the invention of radioisotopic techniques for dating rock samples, geologists determined relative ages for rocks using simple principles of how rocks and their fragments are deposited, and using remains or records of extinct life to correlate samples from different locations. When combined later with the dating of rocks by radioisotopic techniques, a detailed history of Earth could be developed. We work with this history repeatedly throughout the rest of the book. This chapter serves as an introduction to the techniques used to assemble such a record.
CATASTROPHISM VERSUS UNIFORMITARIANISM
When we look at Earth's landforms, we are viewing a snapshot, a moment in a vast span of time during which mountains rise and fall, seas expand over land areas and contract again, and continents shift their positions and grow slowly from new rock added by volcanoes. These processes all require vast amounts of time for their completion, but most do not proceed in a smooth, gradual manner. Instead, geologic processes are a combination of gradual effects and sudden catastrophes. The earthquakes that shake California represent sudden failures of rock after the buildup of stresses over time as one portion of California slowly glides past the other, as we discuss in chapter 9.
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- EarthEvolution of a Habitable World, pp. 75 - 84Publisher: Cambridge University PressPrint publication year: 1998