Chapter 1 - Introduction

Chapter 1 - Introduction - Grotzinger • Jordan...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Grotzinger • Jordan Understanding Earth Sixth Edition Chapter 1: THE EARTH SYSTEM © 2011 by W. H. Freeman and Company Chapter 1: Chapter The The Earth System About the Earth System About • All parts of our planet and all of the interaction of those parts comprise the Earth System. Earth • Earth system is an open system. • Geosystems include: climate, plate tectonics, and the geodynamo. tectonics, Lecture Outline Lecture 1. The scientific method The 2. Geology as a science 3. Earth’s shape and surface 4. Discovery of a layered Earth 5. Earth as a system of interacting 5. components components 6. Overview of geologic time 1. The Scientific Method 1. The goal: explain how the universe works universe 1. The Scientific Method 1. Observation and experimentation Observation Development of an hypothesis or multiple hypotheses as tentative explanation(s) hypotheses Testing (challenging) and experimentation to Testing eliminate hypotheses or revise them eliminate Scientific theory – a coherent set of hypotheses Scientific that explains some aspect of nature that Scientific model – based on many hypotheses Scientific and theories and Thought questions for this chapter Thought How does science differ from religion as a way to How understand the world? understand If no theory can be proved true, why do almost all If geologists believe strongly in Darwin’s theory? geologists 2. Geology as a Science 2. Major questions in geology involve processes Major that operate on large scales and over long time periods. Field observations are supplemented by laboratory experiments. laboratory There are many subfields of geology, including: Oceanography, Ecology, Geophysics, Oceanography, Geochemistry, and Geobiology. Geochemistry, In addition, there are others, including Planetary In Science. Science. 2. Geology as a Science 2. A special aspect: probing Earth’s long probing history – studying the geologic record 2. Geology as a Science 2. Principle of Principle uniformitarianism: uniformitarianism: The present is the key The to understanding the past. 2. Geology as a Science 2. Process comparison: slow versus rapid The most recent layer of sediment is about 250 million years old. S L O The explosive impact of a meteorite created this 1.2­km­wide crater in just a few seconds. W The rocks at the bottom of the Grand Canyon are 1.7–2.0 billion years old. R A P ID 3. Earth’s Shape and Surface 3. Geodesy – study of Earth’s shape and surface • Ancient Greek scholar Eratosthenes’ work showed Ancient that the Earth was spherical. that • Modern research shows that the Earth is not a Modern perfect sphere. perfect • Earth’s topography (surface elevation) ranges nearly Earth’s 20 km from highest to lowest. • Sea level – reference level for all Earth surface and Sea seafloor elevations. seafloor Eratosthenes’ work Eratosthenes’ Topography Topography 4. Discovery of a Layered Earth 4. Seismic waves – illuminate Earth’s interior • Compression and shear waves behave differently and are bent or absorbed at layer boundaries within the Earth. boundaries Earth’s interior is layered according to Earth’s density density • Surface rock density is less than 3.5 g/cm3. Surface • Whole Earth density is 5.5 g/cm3. Whole 3 4. Discovery of a Layered Earth 4. Crust Crust Mantle Crust Mantle Liquid iron outer core Crust Mantle Liquid iron outer core Solid iron inner core 4. Discovery of a Layered Earth The crust: continents are made of lighter The rock and thus literally “float” on material of higher density. 0 (km) 10 20 30 40 50 Oceanic crust (3.0 g/cm3) Continental crust (2.8 g/cm3) Mantle (3.4 g/cm3) Horizontal distance not to scale Moho discontinuity Less dense continental crust floats on denser mantle. 0 (km) 10 20 30 40 50 Oceanic crust (3.0 g/cm3) Continental crust (2.8 g/cm3) Mantle (3.4 g/cm3) Horizontal distance not to scale Moho discontinuity Less dense continental crust floats on denser mantle. 0 (km) 10 20 30 40 50 Oceanic crust (3.0 g/cm3) Continental crust is less dense than oceanic crust. Continental crust (2.8 g/cm3) Mantle (3.4 g/cm3) Horizontal distance not to scale Moho discontinuity 4. Discovery of a Layered Earth 4. Abrupt changes in Abrupt density between Earth’s major interior layers are caused by changes in the chemical composition of those layers. of Thought questions for this chapter Thought Imagine you are a tour guide on a journey from Earth’s Imagine 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? as 5. Earth as a System of Interacting Components Components Earth system – all parts of Earth and the Earth interactions of the parts interactions • climate system climate • plate tectonics system plate • geodynamo system geodynamo Earth is an open system. • exchanges mass and energy with the rest of the cosmos rest Earth system: Earth Interactions Interactions of the climate, plate tectonic, and geodynamo systems. systems. The plate tectonics system: How does The the heat energy inside the Earth move and thus affect the crustal plates? Convection causes hot water to rise… ...where it cools, moves laterally, sinks,… Hot matter from the mantle rises,… Plate …warms, and rises again. …causing plates to form and diverge. Plate Where plates converge, a cooled plate is dragged under… …sinks, warms, and rises again. The geodynamo system: Rapid motion The of the liquid outer core stirs up electrical flow in the solid (iron) inner core – causing Earth’s magnetic field. Earth is an open system. Sun The Sun drives Earth’s external engine. Sun The Sun drives Earth’s external engine. Sun Solar energy is responsible for our climate and weather. The Sun drives Earth’s external engine. Sun Solar energy is Earth’s internal engine responsible is powered by trapped for our climate and heat… weather. The Sun drives Earth’s external engine. Sun Solar energy is Earth’s internal engine responsible is powered by trapped for our climate and heat… weather. …and radioactivity in its interior. The Sun drives Earth’s external engine. Solar energy is Earth’s internal engine responsible is powered by trapped for our climate and heat… weather. Sun Heat radiating from Earth balances solar input and heat from interior. …and radioactivity in its interior. The Sun drives Earth’s external engine. Solar energy is Earth’s internal engine responsible is powered by trapped for our climate and heat… weather. …and radioactivity in its interior. Sun Heat radiating from Earth balances solar input and heat from interior. Meteors move mass from the cosmos to Earth. Thought questions for this chapter Thought How does viewing the Earth as a system of interacting How components help us to understand our planet? Give an example of an interaction between two or more geosystems that could affect the geologic record? geosystems In what general ways are the climate system, the plate In tectonic system, and the geodynamo system similar? In what ways are they different? what Thought questions for this chapter Thought Not every planet has a geodynamo. Why not? If Earth Not did not have a magnetic field, what might be different about our planet? about Based on the material presented in this chapter, what Based can we say about how long ago the three major global geosystems began to operate? geosystems 6. Overview of Geologic Time 6. 6. Overview of Geologic Time 6. 4.6 billion years ago – formation of solar system billion 3.5 billion years ago – formation of geodynamo; billion first known fossils (bacteria) first 2.7 billion years ago – oxygen begins to build billion up in atmosphere up 2.5 billion years ago – large continents in crust billion 2.0 to 1.0 billion years ago – more complex life like algae evolved like 6. Overview of Geologic Time 6. 6. Overview of Geologic Time 6. 600 million years ago – first animals 542 million years ago – evolutionary “big bang” 443 million years ago – first mass extinction of life life 420 million years ago – first land mammals 359, 251, and 200 million years ago – mass extinctions of life extinctions 125 million years ago – first flowering plants 6. Overview of Geologic Time 6. 65 million years ago – last mass extinction (death of the dinosaurs and many other species) (death 5 million years ago – appearance of first hominids hominids 200,000 years ago – appearance of Homo sapiens sapiens 6. Overview of Geologic Time 6. Key terms and concepts Asthenosphere Asthenosphere Climate Climate system Convection Core Crust Earth system Fossil Geodynamo Geologic record Geology Geosystem Inner core Lithosphere Key terms and concepts Magnetic field Magnetic Mantle Outer core Plate tectonic system Principle of uniformitarianism Scientific method Seismic wave Topography ...
View Full Document

This note was uploaded on 07/12/2011 for the course EAS 2600 taught by Professor Ingalls during the Summer '08 term at Georgia Tech.

Ask a homework question - tutors are online