Text: Physical Geology

1. Text: Physical Geology 4th edition by Wicander and Monroe

2. Chapter 1 The Dynamic and Evolving Earth

3. This class is about Physical geologyWhat is Geology? • From the Greek • geo (Earth) logos (reason) • Geology is the study of Earth • Physical geology studies Earth materials, • such as minerals and rocks • as well as the processes operating within • and on Earth’s surface

4. The Role of the Geologist To understand and define:-The structure and composition of the earth-All facets of magma, lava, and volcanic activity-Minerals and rock types-Surface processes: rivers, streams, glaciers, etc.-The earth’s past: both structure origin and life’s evolution with -- Paleontological investigations (studying fossil remains)-Geologic features of other planetsAlso:-To use information learned to find fossil fuels and ores-To learn how to preserve the environment: erosion control, pollution control-Geologic information ties in greatly with advances in technology

5. Physical Geology – centered around the Chemical and Physical aspects of the earth • Geochemistry – the chemical makeup of magma, lava, minerals, rocks, etc. • Mineralogy – the study of the chemical makeup and occurrence of minerals • Petrology – the study of the formation of rocks (which are comprised of minerals) • Vulcanology - the study of volcanics • Seismology – the study of seismic (earthquake) waves • Seismic Tomography – the study of the interior of the earth indirectly by studying the behavior of seismic waves • Tectonics – the study of the formation of the continental plates and the mechanics of their movements • Oceanography – the study of the chemical and physical aspects of the earth’s oceans • Glaciology – the study of the cause and occurrence of glacial episodes • Weathering & Erosion –the disintegration or physical and chemical breakdown and subsequent transportation of earth materials • Geomorphology – the study of the creations of landforms • Soil Sciences – the study of the formation of the various soil types of the world • Economic Resources – the study of the formation and usage of natural resources: petroleum, natural gas, coal, stone materials, etc.

6. Scientific Method • The scientific method • an orderly and logical approach • Gather and analyze facts or data • A hypothesisis a tentative explanation • to explain observed phenomena • Scientists make predictions using hypotheses • based upon Observations • then they Test the predictions • After repeated tests, • if one hypothesis continues to explain the phenomena, • scientists propose it as a theory (Conclusions)

7. Formulation of Theories Theory • colloquial usage - speculation or conjecture • scientific usage • coherent explanation for one or several related natural phenomena • supported by a large body of objective evidence

8. Origin of the Universe • TheBig Bang • occurred 15 billion years ago • and is a model for the beginning of the universe • Age of Earth= 4.5 Billion years old

9. Solar System Configuration

10. Changes in its surface • Changes in life Earth is a Dynamic and Evolving Planet

11. Earth is a System of Interconnected Subsystems • Atmosphere (air and gases) • Hydrosphere (water and oceans) • Biosphere (plants and animals) • Lithosphere (Earth’s rocky surface) • Interior (mantle and core)

12. Plate Tectonic Theory • Lithosphere is broken into individual pieces called plates • Plates move over the asthenosphere • as a result of underlying convection cells

13. Geologic Time Scale

14. Summary • Earth is a system • of interconnected subsystems • Geology is the study of Earth • Historical geology is the study • of the origin and evolution of Earth • Scientific method is • an orderly, logical approach • to explain phenomena, • using data, • formulating and testing hypotheses and theories • Universe began with • a big bang 15 billion years ago

15. Summary • Solar system formed 4.6 billion years ago • by condensation and gravitational collapse • of a rotating interstellar cloud • Earth formed 4.6 billion years ago • as a swirling eddy in the solar system nebula • Moon may have formed • when a planetesimal collided with Earth • 4.6 to 4.4 billion years ago • Earth probably started solid • then differentiated into layers • as it heated and melted

16. Summary • Earth’s layers mostly solidified • into the core, mantle and crust, • with the upper mantle and crust • making up the soft asthenosphere • and the solid lithosphere • Lithosphere is broken into plates • that diverge, converge and • slide sideways past each other • Plate tectonics is a unifying theory • that helps explain features and events • including volcanic eruptions, • earthquakes and mountain forming

17. Summary • Central thesis of organic evolution is • that all living organisms evolved • from organisms that existed in the past • An appreciation • of the immensity of geologic time • is central to understanding Earth’s evolution • Uniformitarianism holds that the laws • of nature have been constant through time • Geology is part of our lives • and our standard of living depends • on our use of natural resources • that formed over billions of years

18. Interactions in Earth’s Subsystems Atmosphere Biosphere Gasesfrom respiration Transport of seeds and spores

19. Interactions in Earth’s Subsystems Wind erosion, transport of water vapor for precipitation Mountainsdivert air movements Atmosphere Lithosphere

20. Interactions in Earth’s Subsystems Source of sediment and dissolved material Water and glacial erosion, solution of minerals Hydrosphere Lithosphere

21. Historical Geology (next semester) • In historical geology we study • changes in our dynamic planet • how and why past events happened • implication for today’s global ecosystems • Principles of historical geology • not only aid in interpreting Earth’s history • but also have practical applications • William Smith, an English surveyor/engineer • used study of rock sequences • to help predict the difficulty of excavation • in constructing canals

22. Evidence for the Big Bang • Universe is expanding • How do we determine the age? • measure the rate of expansion • backtrack to a time when the galaxies • were all together at a single point • Pervasive background radiation of 2.7º above absolute zero • is the afterglow of the Big Bang

23. Big Bang Model • Initial state: • No time, matter or space existed • There is no “before the Big Bang” • Universe consisted of pure energy • During 1st second: • Very dense matter came into existence • The four basic forces separated • gravity, electromagnetic force, 2 nuclear forces • Enormous expansion occurred

24. Big Bang Model (cont.) • 300,000 years later: • atoms of hydrogen and helium formed • light (photons) burst forth for the first time • During the next 200 million years: • Continued expansion and cooling • Stars and galaxies began to form • Elements heavier than hydrogen and helium • began to form within stars by nuclear fusion

25. Features of Our Solar System • In a spiral arm of the Milky Way Galaxy • Sun • 9 planets • 101 known moons (satellites) • a tremendous number of asteroids • most orbit the Sun between the orbits of Mars and Jupiter • millions of comets and meteorites • interplanetary dust and gases

26. Relative Sizes of the Sun and Planets

27. Origin of Our Solar System Solar nebula theory • cloud of gases and dust • formed a rotating disk • condensed and collapsed due to gravity • forming solar nebula • with an embryonic Sun • surrounded by a rotating cloud

28. Embryonic Sun and Rotating Cloud • Planetesimals have formed • in the inner solar system, • and large eddies of gas and dust • remain far from the protosun

29. The Planets • Jovian Planets • Jupiter • Saturn • Uranus • Neptune • large, composed of hydrogen, helium, ammonia, methane, relatively small rocky cores • Terrestrial Planets • Mercury • Venus • Earth • Mars • small, composed of rock, with metal cores

30. Earth’s Very Early History • Started out cool about 4.6 billion years ago • probably with uniform composition/density • Mostly: • silicate compounds • iron and magnesium oxides • Temperature increased. Heat sources: • meteorite impacts • gravitational compression • radioactive decay • Heated up enough to melt iron and nickel

31. Earth’s Differentiation • Differentiation = segregated into layers of differing composition and density • Early Earth was probably uniform • Molten iron and nickel sank to form the core • Lighter silicates flowed up to form mantle and crust

32. Forming the Earth-Moon System • Impact by Mars-sized or larger planetesimal with young Earth • 4.6 to 4.4 billion years ago • ejected large quantity of hot material, • and formed the Moon

33. Forming the Earth-Moon System • Most of the lunar material • came from the mantle of the colliding planetesimal • The material cooled • and crystallized • into lunar layers

34. Forming the Earth-Moon System • Most of the lunar material • came from the mantle of the colliding planetesimal • The material cooled • and crystallized • into lunar layers

35. Moon • Light-colored areas are lunar highlands • Heavily cratered • Provide striking evidence • of massive meteorite bombardment

36. Earth—Dynamic Planet • Earth was also subjected • to the same meteorite barrage • that pock-marked the Moon • Why isn’t Earth’s surface also densely cratered? • Because Earth is a dynamic and evolving planet • Craters have long since been worn away

37. Earth’s Interior Layers • Crust - 5-90 km thick • continental and oceanic • Mantle • composed largely of peridotite • dark, dense igneous rock • rich in iron and magnesium • Core • iron and a small amount of nickel

38. Earth’s Interior Layers • Lithosphere • solid upper mantle and crust • Crust - 5-90 km thick • continental and oceanic • Mantle • composed largely of peridotite • dark, dense igneous rock • rich in iron and magnesium • Asthenosphere • part of upper mantle • behaves plastically and slowly flows • Core • iron and a small amount of nickel

39. Earth’s Interior Layers • Lithosphere • solid upper mantle and crust • broken into platesthat move over the asthenosphere • Asthenosphere • part of upper mantle • behaves plastically and slowly flows

40. Earth’s Crust • outermost layer • continental (20-90 km thick) • density 2.7 g/cm3 • contains Si, Al • oceanic (5-10 km thick) • density 3.0 g/cm3 • composed of basalt

41. Modern Plate Map

42. Plate Tectonic Theory • At plate boundaries • Volcanic activity occurs • Earthquakes occur • Movement at plate boundaries • plates diverge • plates converge • plates slide sideways past each other

43. Continental-continental convergent plate boundary Divergent plate boundary Continental-oceanic convergent plate boundary Oceanic-oceanic convergent plate boundary Divergent plate boundary Mid-oceanic ridge Trench Plate Tectonic Theory • Types of plate boundaries Transform plate boundary

44. Plate Tectonic Theory Influence on geological sciences: • Revolutionary concept • major milestone • comparable to Darwin’s theory of evolution in biology • Provides a framework for • interpreting many aspects of Earth on a global scale • relating many seemingly unrelated phenomena • interpreting Earth history

45. Plate Tectonics and Earth Systems Plate tectonics is driven by convection in the mantle and in turn drives mountain building and associated igneous and metamorphic activity SolidEarth Arrangement of continents affects solar heating and cooling, and thus winds and weather systems Rapid plate spreading and hot-spot activity may release volcanic carbon dioxide and affect global climate Atmosphere

46. Plate Tectonics and Earth Systems Continental arrangement affects ocean currents Rate of spreading affects volume of mid-oceanic ridges and hence sea level Placement of continents may contribute to the onset of ice ages Hydrosphere Movement of continents creates corridors or barriers to migration, the creation of ecological niches, and transport of habitats into more or less favorable climates Biosphere

47. History of Life • The fossil record provides perhaps • the most compelling evidence • in favor of evolution • Fossils are the remains or traces • of once-living organisms • Fossils demonstrate that Earth • has a history of life

48. Geologic Time • From the human perspective time units are in • seconds, hours, days, years • Ancient human history • hundreds or even thousands of years • Geologic history • millions, hundreds of millions, billions of years

49. Geologic Time Scale • Resulted from the work of many 19th century geologists who • pieced together information • from numerous rock exposures, • constructed a sequential chronology • based on changes in Earth’s biota through time • The time scale was subsequently dated in years • using radiometric dating techniques

50. Uniformitarianism • Uniformitarianism is a cornerstone of geology • is based on the premise that present-day processes • have operated throughout geologic time • The physical and chemical laws of nature • have remained the same through time • To interpret geologic events • from evidence preserved in rocks • we must first understand present-day processes • and their results • Rates and intensities of geologic processes • may have changed with time