GLG101 Physical Geology

1. GLG101 Physical Geology Spring 2010 Thomas D. Hoisch http://jan.ucc.nau.edu/~tdh5/glg101_S10.htm

2. NAU Geology Club Contact: Carmen Winn, clw264@nau.edu

4. The Science of Geology • Geology, people, and the environment • Problems and issues addressed by geology include • Natural hazards, resources, and environmental issues

5. The Science of Geology • Some historical notes about geology • The nature of Earth has been a focus of study for centuries • Catastrophism • Uniformitarianism and the birth of modern geology

6. What is Geology? • Geology vs. other sciences • Physical Geology • What do geologists do?

7. Table 1.1

10. Figure 1.2

14. Figure 1.7B

16. Geologic time • Absolute ages: Geologists are now able to determine fairly accurate dates for events in Earth history • Relative ages:Relative dating means that dates are placed in their proper sequence or order without knowing their specific age

17. Geologic time • The magnitude of geologic time • Involves vast times – millions or billions of years • Many processes are very gradual

22. The nature of scientific inquiry • How or why things happen are 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 • Paradigm - a theory with broad implications

23. The nature of scientific inquiry • Scientific methods involves • Gathering facts through observations • Formulation of hypotheses and theories

24. Science – a definition: • “Science is the acceptance of what works and the rejection of what does not” • …Jacob Bronowski - mathematician

25. Earth as a system • *Hydrosphere • Atmosphere • Biosphere • **Solid Earth • Outer space?

27. Figure 1.5

28. Early Earth Evolution • Big Bang • According to NASA WMAP mission – occurred at 13.7 Ga • First stars appears 200 m.y. later

29. Early evolution of Earth • Origin of planet Earth • Most researchers believe Earth and other planets formed at essentially the same time • Nebular hypothesis • Rotating cloud called the solar nebula • Composed of hydrogen and helium • Nebula began to contract about 5 billion years ago

31. Early evolution of Earth • Origin of planet Earth • Most researchers believe Earth and other planets formed at essentially the same time • Nebular hypothesis • Rotating cloud called the solar nebula • Composed of hydrogen and helium • Nebula began to contract about 5 billion years ago

32. Early evolution of Earth • Origin of planet Earth • Nebular hypothesis • Assumes a flat, disk shape with the protosun (pre-Sun) at the center • Inner planets begin to form from metallic and rocky substances • Larger outer planets began forming from fragments of ices (H2O, CO2,and others)

33. Early evolution of Earth • Formation of Earth’s layered structure: the “Great Catastrophe” • Metals sank to the center • Molten rock rose to produce a primitive crust • Chemical segregation established the three basic divisions of Earth’s interior • Primitive atmosphere evolved from gases in Earth’s interior

34. Earth’s internal structure • Layers defined by composition • Crust • Mantle • Core • Layers defined by physical properties • Lithosphere • Asthenosphere • Mesosphere • Inner and Outer Core

35. Earth’s Layered structure Figure 1.16

36. Figure 1.14A

37. Figure 1.14B

38. The face of Earth • Earth’s surface • Continents: average elevation 0.5 miles • Oceans: average depth 2.4 miles • Continents • Mountain belts • Most prominent feature of continents • The stable interior • Also called a craton – composed of shields and stable platforms

39. Figure 1.16

40. The face of Earth • Ocean basins • Continental margins • Includes the continental shelf, continental slope, and the continental rise • Deep-ocean basins • Abyssal plains • Oceanic trenches • Seamounts

41. 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

42. Figure 1.15Left

43. Figure 1.15Right

44. Rocks and the rock cycle • Basic rock types • Igneous rocks • Cooling and solidification of magma (molten rock) • Examples include granite and basalt • Sedimentary rocks • Accumulate in layers at Earth’s surface • Sediments are derived from weathering of preexisting rocks

45. Rocks and the rock cycle • Basic rock types • Sedimentary rocks • Examples include sandstone and limestone • Metamorphic rocks • Formed by “changing” preexisting igneous, sedimentary or other metamorphic rocks • Driving forces are increased heat and pressure • Examples include gneiss and marble

46. Rocks and the rock cycle • The Rock Cycle: One of Earth’s subsystems • One rock changes to another and back with time • Materials change both on the surface and inside the Earth

47. The Rock Cycle Figure 1.23

48. End of Chapter 1