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The Science of Geology Earth: An Introduction to Physical Geology, 10e Tarbuck & Lutgens An Introduction to Geology Earth, 10e - Chapter 1 © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. The Science of Geology, Continued Geology, people, and the environment à Many important relationships exist between people and the natural environment. à Problems and issues addressed by geology include: Geology is the science that pursues an understanding of planet Earth. à Physical geology examines Earth materials and seeks to understand the many processes that operate on our planet. à Historical geology seeks an understanding of the origin of Earth and its development through time. Geologic Time The magnitude of geologic time à Involves vast times—millions or billions of years à An appreciation for the magnitude of geologic time is important because many processes are very gradual. Natural hazards, resources, world population growth, and environmental issues © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. The Science of Geology Geologic Time Some historical notes about geology à The nature of Earth has been a focus of study for centuries. à Catastrophism à Uniformitarianism—the physical, chemical, and biologic laws that operate today have operated throughout the geologic past. © 2011 Pearson Education, Inc. Geologists are now able to assign fairly accurate dates to events in Earth history. Relative dating and the geologic time scale à Relative dating means that dates are placed in their proper sequence or order without knowing their specific age. à Superposition—in a sequence of sedimentary rocks or lava flows, the youngest layer is on top and the oldest layer is on the bottom. © 2011 Pearson Education, Inc. Superposition is well illustrated in the rocks of the Grand Canyon 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. © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. The Geologic Time Scale 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. © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. The Nature of Scientific Inquiry, Continued The Nature of Scientific Inquiry, Continued How or why things happen are explained using: à Hypothesis—a tentative (or untested) explanation à Theory—a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts © 2011 Pearson Education, Inc. Scientific methods involves: à Gathering facts through observations à Formulation of hypotheses and theories There is no fixed path that scientists follow that leads to scientific knowledge. © 2011 Pearson Education, Inc. A View of Earth From Apollo 17 A View of Earth Earth is a planet that is small and self-contained. Earth’s four spheres are: 1. Hydrosphere 2. Atmosphere 3. Biosphere 4. Geosphere © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Earth as a System Earth as a System, Continued Earth is a dynamic planet with many interacting parts or spheres. Earth system science: à Aims to study Earth as a system composed of numerous interacting parts, or subsystems à Employs an interdisciplinary approach to solve global environmental problems What is a system? à Any size group of interacting parts that form a complex whole à Open vs. closed systems Feedback mechanisms à Negative feedback maintains the status quo. à Positive feedback enhances or drives changes. © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Earth as a System, Continued The Interface between the Hydrologic and Rock Cycles Cycles in the Earth System à Hydrologic cycle à Rock cycle An interface is a common boundary where different parts of a system come in contact and interact. © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Earth as a System Early Evolution of Earth The Earth system is powered by the Sun that drives external processes in the following: à Atmosphere à Hydrosphere à At Earth’s surface The Earth system is also powered by Earth’s interior. Origin of planet Earth à Most researchers believe Earth and other planets formed at essentially the same time. à 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. © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Early Evolution of Earth, Continued The Nebular Theory Origin of planet Earth à Nebular hypothesis Assumes a flat, disk shape with the protosun (preSun) 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). © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Early Evolution of Earth Formation of Earth’s layered structure à Metals sank to the center. à Molten rock rose to produce a primitive crust. à Chemical segregation established the three basic divisions of Earth’s interior. à A primitive atmosphere evolved from gases in Earth’s interior . © 2011 Pearson Education, Inc. Earth’s Internal Structure Layers defined by composition: à Crust à Mantle à Core Layers defined by physical properties: à Lithosphere à Asthenosphere à Mesosphere à Inner and outer core © 2011 Pearson Education, Inc. Earth’s Layered Structure The Face of Earth Earth’s surface: à Continents à Oceans Continents: à Mountain belts Most prominent feature of continents à The stable interior Also called a craton—composed of shields and stable platforms © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Earth’s Mountain Belts, Stable Platforms, and Shields The Face of Earth Ocean basins: à Continental margins Includes the continental shelf, continental slope, and the continental rise à Deep-ocean basins: Abyssal plains Oceanic trenches Seamounts © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. The Face of Earth, Continued Ocean basins: à Oceanic ridge system Most prominent topographic feature on Earth Composed of igneous rock that has been fractured and uplifted Rocks and the Rock Cycle Basic rock types: • Igneous rocks à Cooling and solidification of magma (molten rock) à Examples include granite and basalt. • Sedimentary rocks à Accumulate in layers at Earth’s surface à Sediments are derived from weathering of preexisting rocks © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Granite (an Igneous Rock) in Yosemite National Park, CA Rocks and the Rock Cycle Basic rock types: • Sedimentary rocks à Examples include sandstone and limestone. • Metamorphic rocks à Formed by “changing” preexisting igneous, sedimentary, or other metamorphic rocks à Driving forces are heat and pressure. à Examples include gneiss and marble. © 2011 Pearson Education, Inc. Sandstone (a Sedimentary Rock) in Zion National Park, Utah © 2011 Pearson Education, Inc. 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 © 2011 Pearson Education, Inc. The Rock Cycle © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. End of Chapter 1 © 2011 Pearson Education, Inc.
