Exploring Planet Earth: An Oceanography Introduction

1. CHAPTER 1 Introduction to Planet “Earth”Instructor: C. Charles Dong

2. Personal Card Name E-mail • Classes taking this semester • Science/Math Background • Future Major/Career • Expectation of Class Expected Grade/Goal

3. Oceanography • Geological Oceanography • Chemical Oceanography • Physical Oceanography • Biological Oceanography

4. Outline • General Information: earth, oceans • Scientific Methods • Origin of Earth, Ocean, Atmosphere • Internal Structure of Earth

5. Overview • 70.8% Earth covered by ocean • Interconnected global or world ocean • Oceans contain 97.2% of surface water Fig. 1.3ab

6. The four principal oceans • Pacific • Atlantic • Indian • Arctic Plus: • Southern or Antarctic Ocean

7. Comparison of elevation and depth • Average depth 3729 m (12,234 ft) • Average elevation 840 m (2756 ft) • Deepest ocean Mariana Trench 11,022 m (36,161 ft) • Highest continental mountain Mt. Everest 8850 m (29,935 ft)

8. Fig. 1.3cd

9. Exe. 01-01 • Name principle oceans on the earth. • Do you think if “earth” is misnamed for our planet? Why?

10. Scientific method • Observations • Hypotheses • Testing and modification of hypotheses • Theory • Probably true versus absolutely true • Science is continually developing because of new observations

11. Scientific method Fig. 1.9

12. Density is defined as: Mass of unit divided by Volume of unit  = m / V Example: A rock has a mass of 5000 Kg Its volume is 2 m3  = m / V  = 5000 Kg / 2 m3  = 2500 Kg/m3 Density

13. Density stratification • Protoearth experiences density stratification • Density = how heavy something is for its size • Density stratification causes high density material to sink while low density material rises • High density material = rock material and metals • Low density material = gases

14. Origin of the Solar System and Earth • Cloud of gas and space dust (nebula) began to contract about 4.6 billion years ago The Nebular Hypothesis

15. Origin of the Solar System and Earth • Protoplanets were created from the nebula • Protoearth was initially homogenous: • Larger in size than today’s Earth • Had lots of volcanic activity • No continents or oceans • No life

16. Origin of Earth’s atmosphere • Partial melting resulted in outgassing about 4 billion years ago • Similar to gases emitted from volcanoes • Mainly water vapor • Carbon dioxide, hydrogen • Other gases such as methane and ammonia

17. Origin of Earth’s oceans • Water vapor released by outgassing • Condensed as rain • Accumulated in ocean basins • About 4 billion years ago • Ice Comets were also important to adding water to the Earth system

18. Fig. 1.17

19. Ocean salinity • Rain dissolves rocks • Dissolved compounds (ions) accumulate in ocean basins • Ocean salinity based on balance between input and output of ions • Ocean salinity nearly constant over past 4 billion years

20. Exe. 01-02 • Please describe how our solar system, the atmosphere and ocean were formed on the earth? • What is density stratification? • Why is sea water salty?

21. Earth’s internal structure • Highest density material at center (core) • Lowest density material at surface (crust) • Earth layered • Chemical composition • Physical properties

22. Chemical composition • Crust • Low-density, mainly silicate minerals • Mantle • Mainly Fe and Mg silicate minerals • Core • High-density, mainly Fe and Ni

23. Layered Earth Fig. 1.14

24. Physical properties • Lithosphere • Asthenosphere • Mesosphere • Outer core • Inner core

25. Physical properties • Lithosphere • Cool, rigid, brittle • Surface to about 100 km (62 miles) • Asthenosphere • Warm, plastic, able to flow • From 100 km to 700 km (430 miles)

26. Fig. 1.15

27. Lithosphere • Oceanic crust • Underlies ocean basins • Igneous rock basalt • Average thickness 8 km (5 miles) • Relatively high density • 3.0 g/cm3

28. Lithosphere- Crust and Uppermost mantle fused together. • Continental crust • Underlies continents • Igneous rock granite • Average thickness 35 km (22 miles) • Lower density • 2.7 g/cm3

29. Asthenosphere • Upper mantle • Plastic—deforms by flowing • High viscosity—flows slowly

30. Exe. 01-03 • In terms of chemical property, how many layers does the earth have? List them. • In terms of physical property, how many layers does the earth have? List them.

31. Life in oceans • Earliest life forms fossilized bacteria in rocks about 3.5 billion years old • Marine rocks • Life originated in oceans?

32. Stanley Miller’s experiment • Organic molecules formed by ultraviolet light, electrical spark (lightning), and mixture of water, carbon dioxide, hydrogen, methane, and ammonia

33. Fig. 1.18a

34. Age of Earth • Radiometric age dating • Spontaneous change/decay • Half-life • Earth is about 4.6 billion years old

35. Geologic time scale Fig. 1.H

36. Exe. 01-04 • How old is the earth? When did life start on the earth? How do we know these?

37. Summary • General Information: earth, oceans • Scientific Methods • Origin of Earth, Ocean, Atmosphere • Internal Structure of Earth