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Lecture 2: Understanding Earth

Lecture 2: Understanding Earth. Research Methodology. Conclusion. The Nature of Scientific Inquiry. How or why things happen is explained using a Hypothesis – a tentative (or untested) explanation

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Lecture 2: Understanding Earth

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  1. Lecture 2:Understanding Earth

  2. Research Methodology Conclusion

  3. The Nature of Scientific Inquiry • How or why things happen is explained using a • Hypothesis – a tentative (or untested) explanation • Theory – a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts

  4. Evolution of Solar System • Nebular hypothesis • Rotating cloud called the solar nebula • Nebula began to contract about 5 billion years ago • 99.9 % of mass is in the Sun (composed mainly of hydrogen and helium) • Planets in two groups: • Inner planets (Mercury, Venus, Earth, Mars) begin to form from metallic and rocky substances. They are mostly O, Si, Fe, Mg. • Larger outer planets (Jupiter, Saturn, Uranus, Neptune) began forming from fragments of ices (H2O, CO2,and others) and gases.

  5. Evolution of the Solar System

  6. Evolution of the Solar System

  7. Evolution of the Solar System

  8. Evolution of the Solar System

  9. The Solar System

  10. A view of Earth • Earth is a planet that is small and self-contained • Earth’s four spheres • Hydrosphere • Atmosphere • Biosphere • Solid Earth

  11. Earth Internal Structure • Layers defined by composition • Crust • Mantle • Core • Layers defined by physical properties • Lithosphere • Asthenosphere • Mesosphere • Inner and Outer Core

  12. Earth’s layered structure

  13. The face of Earth • Earth’s surface • Continents • Oceans • Continents • Mountain belts • Most prominent feature of continents • The stable interior • Composed of shields and stable platforms

  14. The Continents

  15. The face of Earth • Ocean basins • Oceanic ridge system • Most prominent topographic feature on Earth • Composed of igneous rock that has been fractured and uplifted

  16. Oceanic Ridge System

  17. Dynamic Earth • The theory of plate tectonics • Involves understanding the workings of our dynamic planet • Began in the early part of the twentieth century with a proposal called continental drift – the idea that continents moved about the face of the planet

  18. Dynamic Earth • The theory of plate tectonics • Theory, called plate tectonics, has now emerged that provides geologists with the first comprehensive model of Earth’s internal workings • Plate boundaries • All major interactions among individual plates occurs along their boundaries

  19. Tectonic Plates

  20. Dynamic Earth • Plate boundaries • Divergent boundary – two plates move apart, resulting in upwelling of material from the mantle to create new seafloor • Convergent boundary – two plates move together with subduction of oceanic plates or collision of two continental plates

  21. Iceland is being pulled apart as it sits astride the Mid-Atlantic Ridge.

  22. San Andreas Fault

  23. Dynamic Earth • Plate boundaries • Transform boundaries -located where plates grind past each other without either generating new lithosphere or consuming old lithosphere • Changing boundaries - new plate boundaries are created in response to changes in the forces acting on the lithosphere

  24. Geologic time • The magnitude of geologic time Involves vast times – millions or billions of years • An appreciation for the magnitude of geologic time is important because many processes are very gradual • The big difference between geology and other sciences: TIME (Geologically speaking, not much happens in a human lifetime!) • Therefore, geologists use millions of years as the standard unit of time

  25. Age of Earth • ~ 4,600 million years • Radioactive minerals • Radium, uranium, lead • Salts in the oceans and its accumulation (not accurate) • Fro younger ages, deposits and C14

  26. The geologic time scale

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