Understanding Earth Lecture Slides PDF

John Grotzinger Thomas H. Jordan Understanding Earth EIGHTH EDITION t Lecture Slides CHAPTER 1 The Earth System Copyright © 2020, W.H. Freeman and Company  About the Earth System All parts of our planet and all of the interactions of those parts comprise...

John Grotzinger Thomas H. Jordan Understanding Earth EIGHTH EDITION t Lecture Slides CHAPTER 1 The Earth System Copyright © 2020, W.H. Freeman and Company  About the Earth System All parts of our planet and all of the interactions of those parts comprise the Earth system. The Earth system is an open system. Geosystems include: climate, plate tectonics, and the geodynamo.  Lecture Outline 1. The scientific method 2. Geology as a science 3. Earth’s shape and surface 4. Discovery of a layered Earth 5. Earth as a system of interacting components 6. Overview of geologic time  1. The Scientific Method (1 of 6) The goal: Explain how the universe works  1. The Scientific Method (2 of 6) Observation and experimentation  1. The Scientific Method (3 of 6) Observation and experimentation Development of a hypothesis or multiple hypotheses as tentative explanation(s)  1. The Scientific Method (4 of 6) Observation and experimentation Development of a hypothesis or multiple hypotheses as tentative explanation(s) Testing (challenging) and experimentation to eliminate hypotheses or revise them  1. The Scientific Method (5 of 6) Observation and experimentation Development of a hypothesis or multiple hypotheses as tentative explanation(s) Testing (challenging) and experimentation to eliminate hypotheses or revise them Scientific theory – a coherent set of hypotheses that explains some aspect of nature  1. The Scientific Method (6 of 6) Observation and experimentation Development of a hypothesis or multiple hypotheses as tentative explanation(s) Testing (challenging) and experimentation to eliminate hypotheses or revise them Scientific theory – a coherent set of hypotheses that explains some aspect of nature Scientific model – based on many hypotheses and theories  Thought questions for this chapter (1 of 4) How does science differ from religion as a way to understand the world? If no theory can be proved true, why do almost all geologists believe strongly in Darwin’s theory?  2. Geology as a Science (1 of 7) Major questions in geology involve processes that operate on large scales and over long time periods.  2. Geology as a Science (2 of 7) Major questions in geology involve processes that operate on large scales and over long time periods. Field observations are supplemented by laboratory experiments.  2. Geology as a Science (3 of 7) Major questions in geology involve processes that operate on large scales and over long time periods. Field observations are supplemented by laboratory experiments. There are many disciplines related to geology, including: Oceanography and Ecology. And subfields of geology such as: Geophysics, Geochemistry, and Geobiology.  2. Geology as a Science (4 of 7) Major questions in geology involve processes that operate on large scales and over long time periods. Field observations are supplemented by laboratory experiments. There are many disciplines related to geology, including: Oceanography and Ecology. And subfields of geology such as: Geophysics, Geochemistry, and Geobiology. In addition, there are others, including Planetary Science.  2. Geology as a Science (5 of 7) A special aspect: Probing Earth’s long history – studying the geologic record  2. Geology as a Science (6 of 7) Principle of uniformitarianism: The present is the key to understanding the past.  2. Geology as a Science (7 of 7) Process comparison: slow versus rapid Figure 1.6  3. Earth’s Shape and Surface Geodesy – study of Earth’s shape and surface Ancient Greek scholar Eratosthenes’ work showed that Earth was spherical. Modern research shows that Earth is not a perfect sphere. Earth’s topography (surface elevation) ranges nearly 20 km from highest to lowest. Sea level – reference level for all Earth surface and seafloor elevations. Eratosthenes’ work determining the size of Earth Pages 8-9 Earth’s Topography Figure 1.7 4. Discovery of a Layered Earth (1 of 5) Seismic waves – illuminate Earth’s interior Compression and shear waves behave differently and are bent or absorbed at layer boundaries within Earth. 4. Discovery of a Layered Earth (2 of 5) Seismic waves – illuminate Earth’s interior Compression and shear waves behave differently and are bent or absorbed at layer boundaries within Earth. Earth’s interior – layered according to density Surface rock density is less than 3.5 g/cm3. Whole Earth density is 5.5 g/cm3. Core density must be about 8 g/cm3. 4. Discovery of a Layered Earth (3 of 5) Figure 1.8 4. Discovery of a Layered Earth (4 of 5) The crust: Continents are made of lighter rock and thus literally “float” on material of higher density. Figure 1.10 4. Discovery of a Layered Earth (5 of 5) Abrupt changes in density between Earth’s major interior layers are caused by changes in the chemical composition of those layers. Figure 1.11  Thought questions for this chapter (2 of 4) Imagine you are a tour guide on a journey from Earth’s surface to the center. How would you describe the material that your tour group encounters on the way down? Why is the density of material always increasing as you go down?  5. Earth as a System of Interacting Components (1 of 2) Earth is an open system. exchanges mass and energy with the rest of the cosmos  5. Earth as a System of Interacting Components (2 of 2) Earth is an open system. exchanges mass and energy with the rest of the cosmos Earth system – all parts of Earth and the interactions of the parts climate system plate tectonics system geodynamo system Earth is an open system. (1 of 7) Figure 1.12 Earth is an open system. (2 of 7) Figure 1.12 Earth is an open system. (3 of 7) Figure 1.12 Earth is an open system. (4 of 7) Figure 1.12 Earth is an open system. (5 of 7) Figure 1.12 Earth is an open system. (6 of 7) Figure 1.12 Earth is an open system. (7 of 7) Figure 1.12  Figure 1.13 The Earth system: Interactions of the climate, plate tectonic, and geodynamo systems.  Figure 1.15 The plate tectonic system: How does the heat energy inside Earth move and thus affect the crustal plates?  Figure 1.16 The geodynamo system: Rapid motion of the liquid outer core stirs up electrical flow in the solid (iron) inner core, causing Earth’s magnetic field.  Thought questions for this chapter (3 of 4) How does viewing Earth as a system of interacting components help us to understand our planet? Give an example of an interaction between two or more geosystems that could affect the geologic record. In what general ways are the climate system, the plate tectonic system, and the geodynamo system similar? In what ways are they different?  Thought questions for this chapter (4 of 4) Not every planet has a geodynamo. Why not? If Earth did not have a magnetic field, what might be different about our planet? Based on the material presented in this chapter, what can we say about how long ago the three major global geosystems began to operate? 6. Overview of Geologic Time (1 of 6) Figure 1.18  6. Overview of Geologic Time (2 of 6) 4.6 billion years ago – formation of solar system 3.5 billion years ago – formation of geodynamo; first known fossils (bacteria) 2.7 billion years ago – oxygen begins to build up in atmosphere 2.5 billion years ago – large continents in crust 2.0 to 1.0 billion years ago – more complex life, such as algae, evolved 6. Overview of Geologic Time (3 of 6) Figure 1.18  6. Overview of Geologic Time (4 of 6) 600 million years ago – first animals 542 million years ago – evolutionary “big bang” 443 million years ago – first mass extinction of life 420 million years ago – first land mammals 359, 251, and 200 million years ago – mass extinctions of life 125 million years ago – first flowering plants  6. Overview of Geologic Time (5 of 6) 65 million years ago – last mass extinction (death of the dinosaurs and many other species) 5 million years ago – appearance of first hominids 200,000 years ago – appearance of Homo sapiens 6. Overview of Geologic Time (6 of 6) Figure 1.18