GEO NOTES

GEO NOTES - CHAPTER 1 1 The scientific method a The goal to...

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Unformatted text preview: CHAPTER 1 1) The scientific method a) The goal- to explain how natural phenomena works b) Based on methodical observation and experiments to develop a tentative, testable hypothesis (multiple) c) Challenge hypothesis until it is theory d) Develop a scientific model to represent some aspect of nature 2) Discovery of a layered Earth- an illustration of the scientific method a) Key observations- density i) Surface rock density is relatively low ex: granite 2.7g/cm 3 ii) However the whole earth density is 5.5 g/cm 3 iii) Mantle nodules in volcanic rocks have higher density (3.5 g/cm 3 ) b) Seismic wave behavior i) Compression (P) and shear (S) waves behave differently and are bent, absorbed or reflected at layer boundaries within the earth ii) P waves= compressional (faster); S waves= shear (slower) iii) P waves travel through solids, liquids, and gases iv) S waves only travel though solids v) Their travel velocity depends on the density of material c) Crust: continents are made of lighter rock and thus literally float on material of higher density- compositional break (Moho) i) Less dense continental crust floats on mantle ii) Oceanic crust is more dense than continental 3.0g/cm 3-2.87g/cm 3 iii) abrupt changes in density between earths major interior layers are caused by changes in the chemical composition of those layers d) Heating and differentiation of the earth i) Accretion (kinetic energy addition) ii) Compression (gravitational and kinetic energy addition) iii) Radioactive elements (spontaneous decay releases heat): long-lived heating effect 3) The earth system a) The earth system relates to the interactions of all the Geoystems i) Climate system ii) Plate tectonic system (1) How does the heat energy inside the earth move and thus affect the crustal plates? (a) Convection causes hot material to rise (b) I t cools and moves laterally, sinks (c) Warms and r ises again (2) 13 major lithospheric plates iii) Geodynamo system (1) Rapid motion of the liquid outer core stirs up electrical flow in the solid (iron) inner core causing earth’s magnetic field b) The sun drives the earth’s external engine c) Solar energy is responsible for our climate and weather d) Earths internal engine is powered by trapped heat and radioactivity in its interior 4) The geologic record a) James Hutton’s principle of uniformitarianism- geologic processes of today worked much the same way in the geologic past i) Some processes are slow like sediment accumulation on the sea floor ii) Some processes are rapid ex: meteorite impact or volcanic eruption b) Geologic record- information preserved in rocks (geo-clues) 5) Overview of geologic time (deep time) a) The geologic time element is difficult for humans to perceive i) we deal with time frames of 10s of years b) Geologic time makes nearly imperceptible rates on a human scale fast on geologic scale c) Timeline i) 4560 MYA Earth and planets form ii) 4510 MYA Moon forms iii) 4470 MYA oldest lunar rocks iv) 4000 MYA oldest continental...
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This note was uploaded on 04/19/2008 for the course GEOL 1003 taught by Professor Hanor during the Spring '08 term at LSU.

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GEO NOTES - CHAPTER 1 1 The scientific method a The goal to...

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