GEOL 1001 annie's notes - Geol 1001 Chapter 1 09:36 Topics 1 What is geology Geology is the science that pursues an understanding of planet Earth

GEOL 1001 annie's notes - Geol 1001 Chapter 1 09:36 Topics...

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Geol 1001: Chapter 1 09:36 Topics 1. What is geology? 2. Geologic Time Overview The geologic record Process comparison: slow versus rapid rates A lot of geologic events happen on different time scales Geologic time Relative dating
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Events are placed in their proper sequence or order without knowing their specific age Law of superposition In a sequence of sedimentary rocks or lava flows, the youngest layer is on top and the oldest layer is on the bottom. Principle of fossil succession Fossil organisms succeed one another in a definite and determined order, and therefore any time period can be recognized by its fossil content Radiometric dating: Gives actual dates based on known rates of decay for radioactive isotopes (e.g. Uranium (parent isotope) decays into lead (daughter isotope)) Oldest material Detrital Zircons from a conglomerate at Jack Hills, Australia (4.4. billion years) Geologic time scale Eons, eras, periods, epochs Years added after divisions Precambrian 88% time 3. Scientific Inquiry The Scientific Method 1. Start with observations 2. Hypothesis : a testable explanation, can be many to explain the same phenomenon (must be TESTABLE) 3. Experiments to test hypothesis 4. Accept, modify, reject the hypothesis Theory: Well-tested hypothesis, widely-accepted view that the scientific community agrees best explains the observable facts
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4. Earth as a system Earth’s spheres 1. Hydrosphere: all salt water & fresh water (above & below ground) water covers ~71% of Earth’s surface 2. Atmosphere thin envelope of gas around the Earth, protects from heat & UV radiation 3. Biosphere all life on Earth 4. Geosphere: the solid Earth, 6400 m from surface to center Earth as a system Components (spheres) interact in the Earth system Closed system Movement of energy but no movement of matter in/out of system Open system ********* Solar energy, condensation, precipitation, etc, MAP 5. Early earth evolution 14 Ga (billion years): Big Bang Explosion
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H & He cooled, condensed into stars & galaxies Nebular theory: Bodies in the solar system evolved from enormous, rotating cloud (solar nebula) 5 Ga: Nebula contracts (gravity),rotates faster flat, disc with protosun (like an ice skater pulling her arms in & therefore spinning faster) 6. Earth’s Internal & External Structure The Crust 1. Oceanic 7 km, AKA 5 mi Basalt Relatively homogeneous 2. Continental 35-40 km, AKA 25 mi (to >70 km, 40 mi!)
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