This preview shows page 1. Sign up to view the full content.
Unformatted text preview: The Earth System
Professor John Platt Material covered: Understanding Earth 5th edition Chapter 1, pp. 1-16 15:19 Earth Sy stem 1 Today's lecture The Scientific Method An example of a hypothesis The Earth is a sphere An example of a model: The layered Earth An example of a theory Isostasy "The present is the key to the past" The Earth System
15:19 Earth Sy stem 2 The Scientific Method Science is based on the empirical method: We can understand the world by developing scientific explanations for observations Scientific explanations can be considered valid only if they account for the observations What we observe has a physical explanation, even if it's beyond our present capacity to understand it We assume that basic physical laws are the same at all places and times 15:19 Earth Sy stem 3 Types of Scientific Explanations Hypothesis a tentative explanation of observations and experiments, proposed for further testing Theory a set of hypotheses that has survived repeated challenges and has accumulated a substantial body of observational support Scientific model a representation of some aspect of nature based on a set of hypotheses and established theories 15:19 Earth Sy stem 4 15:19 Earth Sy stem 5 Scientific Method No explanation, no matter how believable or appealing, is closed to question Theories can never be proved! A hypothesis, theory, or model that is confirmed by repeated observations and experiments gains credibility The longer a theory holds up to all scientific challenges, the more confidently it is held One of the most important tests of a scientific explanation is to compare its predictions with observations
15:19 Earth Sy stem 6 Example of an hypothesis: We live on a sphere. Eratosthenes 15:19 BC - 194 BC 276 Earth System Christopher Columbus 7 Example of an hypothesis: We live on a sphere.
Alexandria 800 km Syene (Aswan) Eratosthenes 15:19 BC - 194 BC 276 Earth System 8 Example of an hypothesis: We live on a sphere.
Alexandria 800 km Syene (Aswan) 15:19 Earth System 9 800 km x 360/7 ! 40,000 km 15:19 Earth System 10 Example of a Model:
Earth is a sphere with a circumference of 40,000 km
C = 2" R 10,000 km R = 6370 km 15:19 Earth System 11 Crust Mantle Liquid iron outer core Solid iron inner core Example of a model: The Layered Earth
15:19 Earth Sy stem 12 Example of a Theory: Isostasy The flotation principle The crust "floats" on the underlying denser mantle Topography is controlled by the thickness and density of the crust
15:19 Earth Sy stem 13 Earth's Topography 15:19 Earth Sy stem 14 Earth's Crust The crust is a compositional layer lying above the mantle. Oceanic crust is thin and dense Continental crust is thick and has lower density
15:19 Earth Sy stem 15 "The Present is the Key to the Past" 15:19 Earth Sy stem 16 "The present is the Key to the Past" A guiding principle in geologic research Not a hypothesis Not a theory Not a model
15:19 Earth Sy stem 17 The Earth System The Climate System The Plate Tectonic System The Geodynamo System 15:19 Earth Sy stem 18 The Earth System The Earth System is in fact a set of interacting systems 15:19 Earth Sy stem 19 Earth is an open system that exchanges energy and mass with its surroundings 15:19 Earth Sy stem 20 ...
View Full Document
This note was uploaded on 02/27/2008 for the course GEOL 105Lg taught by Professor Davis,platt during the Spring '07 term at USC.
- Spring '07