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Unformatted text preview: Scientific Method • The scientific method- a research strategy based on the principle that every physical event has a physical explanation • Data interpretation and hypothesis construction- tentative explanation based on data collected through observation and experimentation. With a hypothesis you can predict. • Theory- a hypothesis that has survived repeated challenges and experiments • Data collecting - Hypothesis constructing - n x Hypothesis testing Theory • Hypothesis testing never stops, and even well established hypotheses need to be tested against new data. • Uniformitarianism- Interpretation of historical data based on present- day geological phenomena • James Hutton- Father of Geology “The Theory of the Earth” (1785) • Charles Lyell- Geologist “Principles of Geology” • “The past history of our globe must be explained by what can be seen to be happening now” • “The present is the key to the past” • Methodological o Uniformity of Law: Foundation of historical science. Ex: Gravity o Uniformity of Process: Actualism. Ex: Water Cycle. Not Valid • Substantive o Uniformity of Rate and magnitude: Gradualism (Things do change, but at constant rate). Not Valid o Uniformity of Condition: nondirectionism (Things don’t change; or the Earth system has been maintaining the same quilibrium state). Not Valid • Catastrophism • Found by Curvier and Brongniart • Studied fossils in the Paris Basin • Used the Bible’s Noah’s Arc story to hypothesize about the rocks and fossils found in the Paris Basin • Dramatic changes in successive fossil assemblages • Believed that these changes were caued by total extinction resulted from catastrophes akin to the Noachian Deluge, followed by successive creations of new species • We now know that these abrupt changes are largely due to unconformities or missing record • Catastrophism has not been totally abandoned; it is particularly instructive in later studies on mass extinctions Steno’s Principles • Rocks deposited in the ocean (sedimentary rocks) form layers (strata) and follow the following principles: o The principle of original horizontality o The principle of original lateral continuity o The principle of superposition0 important for relative dating. • Why some strata are not horizontal, contra Steno’s first principle? • Hutton’s unconformity with basal “puddlingstone”, or conglomerate, along the River Jed, Scotland. • Some rock layers are vertical mostly because of earthquakes, lava, tectonic events, etc. o These rocks are then pushed above sea level. Then pushed down below sea level to make room for rocks above it • Time Missing: Anglar Unconformity • Unconformity: A substantial break or gap in the geologic record: o Angular Unocnformtiy: An unconformity between two groups of rocks whose bedding planes are not parallel: (older rocks tilted and eroded) o Parallel Unconformity: An unconformity between two group sof rocks...
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- Fall '08
- Plate Tectonics, Sedimentary rocks, land plants, oceanic crust