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Unformatted text preview: Geology notes The Earth as a System • The Earth’s core generates a magnetic field • The Earth’s magnetic field protects the earth’s surface from the solar wind Solar wind- radiation that could harm the atmosphere • w/o magnetic field life might not have evolved on Earth • Life sequesters carbon keeping the earth’s surface cool • w/o life Earth would be like Venus w/ thick hot poisonous atmosphere and no oceans or liquid water The Earth System The Scientific Method • depends on the empirical method • observations and experiments • seek explanations that are consistent with scientific principles • explanations must account for the observations or they are rejected We assume that basic physical laws are the same at all places and times (sometimes challenged). A hypothesis must be supported by observations. Scientific Hierarachy Hypothesis – a tentative explanations 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 No explanation, no matter how believable or appealing is closed to question • Theories can never be proved such as gravity is still challenged and we can measure changes in gravity A hypothesis, theory, or model that is confirmed by repeated observations and experiments gains creditability • Longer a theory holds up to all scientific challenged the more confidently it is held Comparing a model’s prediction with observations tests whether the hypotheses that went into the model are consistent • Hypothesis- we live on a sphere (Eratostheses and Christopher Columbus supported this and went out to find evidence. A lunar eclipse is a good example that shows that the earth is a sphere) “The present is the key to the past”- guiding principle The Layered Earth- Scientific model (decades of observations) • Crust- 35km made up of the elements Si, Na, K, Al, Fe, and Mg. It has a lower density than mantle • Mantle- 7/8 of the Earth’s volume, it is solid rock. Made up of Mg 2 Si O 4- olivine about 3000 km in radius • Liquid iron outer core and Solid Iron inner core- r= 3000km v= 1/8 of the earth. It is half the diameter of the earth Topography Averages – Ocean 5km below sea level, 9km above sea level Mt Everest Earth’s Crust • The crust is a compositional layer lying above the mantle (3.4 g/cmThe crust is a compositional layer lying above the mantle (3....
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This note was uploaded on 10/05/2008 for the course GEOL 105Lg taught by Professor Davis,platt during the Fall '07 term at USC.
- Fall '07