1. Earth: An Introduction to Physical Geology, 10e
Tarbuck & Lutgens
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2. Stan Hatfield Southwestern Illinois College
An Introduction to Geology
Earth, 10e - Chapter 1
Stan Hatfield
Southwestern Illinois College
© 2011 Pearson Education, Inc.

3. © 2011 Pearson Education, Inc.
The Science of Geology
Geology is the science that pursues an understanding of planet Earth.
Physical geology examines Earth materials and seeks to understand the many processes that operate on our planet.
Historical geology seeks an understanding of the origin of Earth and its development through time.
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4. The Science of Geology, Continued
Geology, people, and the environment
Many important relationships exist between people and the natural environment.
Problems and issues addressed by geology include:
Natural hazards, resources, world population growth, and environmental issues
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Geologic Time
The magnitude of geologic time
Involves vast times—millions or billions of years
An appreciation for the magnitude of geologic time is important because many processes are very gradual.
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The Science of Geology
Some historical notes about geology
The nature of Earth has been a focus of study for centuries.
Catastrophism
Uniformitarianism—the physical, chemical, and biologic laws that operate today have operated throughout the geologic past.
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Geologic Time
Geologists are now able to assign fairly accurate dates to events in Earth history.
Relative dating and the geologic time scale
Relative dating means that dates are placed in their proper sequence or order without knowing their specific age.
Superposition—in a sequence of sedimentary rocks or lava flows, the youngest layer is on top and the oldest layer is on the bottom.
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8. Superposition is well illustrated in the rocks of the Grand Canyon
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Geologic Time
Relative dating and the geologic time scale
Principle of fossil succession—fossil organisms succeed one another in a definite and determinable order. Therefore, any time period can be recognized by its fossil content.
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10. The Geologic Time Scale
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11. The Nature of Scientific Inquiry
Science assumes the natural world is consistent and predictable.
The goal of science is to discover patterns in nature and use the knowledge to make predictions.
Scientists collect data through observation and measurements.
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12. The Nature of Scientific Inquiry, Continued
How or why things happen are explained using:
Hypothesis—a tentative (or untested) explanation
Theory—a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts
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13. The Nature of Scientific Inquiry, Continued
Scientific methods involves:
Gathering facts through observations
Formulation of hypotheses and theories
There is no fixed path that scientists follow that leads to scientific knowledge.
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A View of Earth
Earth is a planet that is small and self-contained.
Earth’s four spheres are:
Hydrosphere
Atmosphere
Biosphere
Geosphere
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15. A View of Earth From Apollo 17
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Earth as a System
Earth is a dynamic planet with many interacting parts or spheres.
Earth system science:
Aims to study Earth as a system composed of numerous interacting parts, or subsystems
Employs an interdisciplinary approach to solve global environmental problems
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17. Earth as a System, Continued
What is a system?
Any size group of interacting parts that form a complex whole
Open vs. closed systems
Feedback mechanisms
Negative feedback maintains the status quo.
Positive feedback enhances or drives changes.
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18. Earth as a System, Continued
Cycles in the Earth System
Hydrologic cycle
Rock cycle
An interface is a common boundary where different parts of a system come in contact and interact.
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19. The Interface between the Hydrologic and Rock Cycles
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Earth as a System
The Earth system is powered by the Sun that drives external processes in the following:
Atmosphere
Hydrosphere
At Earth’s surface
The Earth system is also powered by Earth’s interior.
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21. Early Evolution of Earth
Origin of planet Earth
Most researchers believe Earth and other planets formed at essentially the same time.
Nebular hypothesis
Solar system evolved from an enormous rotating cloud called the solar nebula
Composed of hydrogen and helium
Nebula began to contract about 5 billion years ago.
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22. Early Evolution of Earth, Continued
Origin of planet Earth
Nebular hypothesis
Assumes a flat, disk shape with the protosun (pre-Sun) at the center
Inner planets begin to form from metallic and rocky substances.
Larger outer planets began forming from fragments of ices (H2O, CO2 , and others).
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The Nebular Theory
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24. Early Evolution of Earth
Formation of Earth’s layered structure
Metals sank to the center.
Molten rock rose to produce a primitive crust.
Chemical segregation established the three basic divisions of Earth’s interior.
A primitive atmosphere evolved from gases in Earth’s interior .
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25. Earth’s Internal Structure
Layers defined by composition:
Crust
Mantle
Core
Layers defined by physical properties:
Lithosphere
Asthenosphere
Mesosphere
Inner and outer core
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26. Earth’s Layered Structure
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The Face of Earth
Earth’s surface:
Continents
Oceans
Continents:
Mountain belts
Most prominent feature of continents
The stable interior
Also called a craton—composed of shields and stable platforms
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28. Earth’s Mountain Belts, Stable Platforms, and Shields
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The Face of Earth
Ocean basins:
Continental margins
Includes the continental shelf, continental slope, and the continental rise
Deep-ocean basins:
Abyssal plains
Oceanic trenches
Seamounts
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30. The Face of Earth, Continued
Ocean basins:
Oceanic ridge system
Most prominent topographic feature on Earth
Composed of igneous rock that has been fractured and uplifted
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31. Rocks and the Rock Cycle
Basic rock types:
Igneous rocks
Cooling and solidification of magma (molten rock)
Examples include granite and basalt.
Sedimentary rocks
Accumulate in layers at Earth’s surface
Sediments are derived from weathering of preexisting rocks
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32. Granite (an Igneous Rock) in Yosemite National Park, CA
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33. Rocks and the Rock Cycle
Basic rock types:
Sedimentary rocks
Examples include sandstone and limestone.
Metamorphic rocks
Formed by “changing” preexisting igneous, sedimentary, or other metamorphic rocks
Driving forces are heat and pressure.
Examples include gneiss and marble.
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34. Sandstone (a Sedimentary Rock) in Zion National Park, Utah
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35. Rocks and the Rock Cycle
The rock cycle: one of Earth’s subsystems
The loop that involves the processes by which one rock changes to another.
Illustrates the various processes and paths as Earth materials change both on the surface and inside the Earth
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The Rock Cycle
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End of Chapter 1
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