Classroom presentations to accompany Understanding Earth , 3rd edition

1. Classroom presentations to accompany Understanding Earth, 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 1 Building a Planet

2. Understanding the Earth System

4. ...just like chemistry and physics! Geologists face the special challenge of not being able to do experiments in the sense that chemists and physicists do. Geology is a science...

5. The universe is sensible and governed by immutable rules. Scientific principles

6. The scientific method 1) Make an observation about the sensible world. 2) Develop an explanation (hypothesis) that predicts the outcome of other observations or experiments.

7. 3a) Make new experiments. The scientific method (cont.) 3b) Make new observations.

8. The scientific method (cont.) return to step 2 return to step 3 4) Do the results match the predictions of the hypothesis ? Reject the hypothesis no yes

9. The scientific method Simply put: Always ask yourself, “How will I know if I’m wrong?”

10. A hypothesis is an explanation initially offered for a set of observations. When a hypothesis withstands many tests it may be called a theory. A theory for which it seems there to be no sensible reasons to challenge is called a law. Hypothesis - Theory - Law

11. Parsimonious(is the simplest explanation available) Consilient(explains a wide range of phenomena) A good theory is...

12. Observational: maps rock types, distributions, structures microscopic investigations Experimental: chemical geophysical What are the data used in geology?

13. Since geologists are interested in systems that are very big (hundreds of km) and that have evolved over long periods of time (millions of years), they cannot conduct controlled experiments. They must observe the results of Nature’s experiments that are already complete. The problem of experiments

14. Natural laws do not change — however, rates and intensity of processes may. Uniformitarianism The present is the key to the past — James Hutton

15. The big difference between geology and other sciences: TIME (Geologically speaking, not much happens in a human lifetime!) Rates of geologic processes: µm/year to cm/year Big earthquakes may displace the ground several meters in a few seconds, but they occur only every 500 years or so. TIME

16. The rates of geologic processes are almost always slower than the rates of human effects on the environment. TIME

17. The official SI unit of time is the second, but it would be very inconvenient to use this unit in geology; even the year is too small in most cases. Therefore, geologists use millions of years as the standard unit of time: 10 Ma = 10 million years ago 10 m.y. = an interval of time lasting 10 million years TIME

18. Some geologic features take millions of years to form. Fig. 1.1 Carr Clifton

19. Others take seconds! Fig. 1.1 John Sanford/Photo Researchers

20. Pick a theory, any theory, but it must be consistent with these facts: 1) Planets all revolve around the Sun in the same direction in nearly circular orbits. 2) The angle between the axis of rotation and the plane of orbit is small (except Uranus). 3) All planets (except Venus and Uranus) rotate in the same direction as their revolution; their moons do, too. Origin of solar system

21. 4) Each planet is roughly twice as far as the next inner planet is from the Sun (the Titus-Bode rule). 5) 99.9 % of mass is in the Sun; 99 % of angular momentum is in the planets. 6) Planets in two groups: terrestrial (inner): Mercury, Venus, Earth, Mars Mercury is mostly Fe ( = 5.4) Jovian (outer): Jupiter, Saturn, Uranus, Neptune. Jupiter mostly gas and ice (  = 0.7) Pluto ???? 7) Terrestrial planets are mostly O, Si, Fe, Mg. The Sun is almost entirely H & He (also important in Jovian planets). Origin of solar system

22. Primeval slowly rotating gas cloud (nebula) condensed into several discrete blobs. fitsdoesn't fit rotation angular momentum mass Nebular hypothesis

23. Portions of the Sun were torn off by a passing star: planetesimals then collided to form planets. Problems: gases coming from Sun would be too hot to condense; stellar collision exceedingly rare. Collision hypothesis

24. Large gas cloud begins to condense. Most mass in the center, turbulence in outer parts. Turbulent eddies collect matter meters across; small chunks grow and collide, eventually becoming large aggregates of gas and solid chunks. Protoplanets, much bigger than present planets, eventually contracted due to their own gravity. Protoplanet hypothesis

25. Evolution of the Solar System Fig. 1.2a

26. Evolution of the Solar System Fig. 1.2b

27. Evolution of the Solar System Fig. 1.2c

28. Evolution of the Solar System Fig. 1.2d

29. Our Solar System Fig. 1.3

30. Only a little smaller than Mercury (small planet in two-planet system). Surface of the moon very different from the surface of Earth. No atmosphere, therefore, no weathering. The Moon

31. Formation of the Moon Fig. 1.4 Alfred T. Kamajian

32. Timeline for the Sun, Earth, and Moon Fig. 1.5 Extensively modified from D.J. DePaolo, Nature

33. The evolutionary course is significantly influenced by the initial state. We know the state of the Earth today relatively well; knowing the beginning will help constrain the in between. Why worry about the beginning?

34. A Differentiating Planet Fig. 1.6

35. An Early Homogeneous Earth Fig. 1.6a

36. Differentiation Begins Fig. 1.6b

37. Fig. 1.6c

38. Relative Abundance of Elements Fig. 1.7

39. Lithosphere Hydrosphere Atmosphere Biosphere Fig. 1.9

40. Interacting Earth Systems Fig. 1.8

41. The unifying concept of the Earth sciences. The outer portion of the Earth is made up of about 20 distinct “plates” (~ 100 km thick) that move relative to each other. This motion is what causes earthquakes and forms mountain ranges. Plate tectonics

42. lithosphere: the outer rigid shell of the earth (~ 100 km). The plates are composed of this material. asthenosphere: part of mantle beneath lithosphere. The lithosphere rides ONTOP of the asthenosphere. Plate tectonics

43. Earth’s Crust, Lithosphere, and Asthenosphere Fig. 1.11

44. Present-day Plates Fig. 1.12 Pete W. Sloss, NOAA-NESDIS-NGDC

45. Convection in the Kitchen Fig. 1.13a

46. Convection in the Earth Fig. 1.13b

47. 1. Divergent 2. Convergent 3. Strike-slip (transform,conservative) Three types of plate boundaries

48. Three Types of Plate Boundaries Fig. 1.14

49. Fig. 1.14a

50. Fig. 1.14b