CHAPTER 1 Introduction to Planet “Earth”

1. CHAPTER 1 Introduction to Planet “Earth”

2. Overview • 70.8% Earth covered by ocean • Interconnected global or “world ocean” • Oceans contain 97.2% of surface water • 99% of earth’s biosphere is in the ocean!!

3. Introduction • Oceanography – the description of the oceans • Interdisciplinary • Geological • Chemical • Physical • Biological

4. Global Ocean4 principal oceans + plus one • Pacific • Largest, deepest • Atlantic • Second largest • Indian • Mainly in Southern Hemisphere • Arctic • Smallest, shallowest, ice-covered • Often consider only a “sea” • + Antarctic or Southern Ocean • Connects Pacific, Atlantic, and Indian • South of about 50o S latitude

5. The “Seven” Seas • Smaller and shallower than oceans • Salt water • Usually enclosed by land • Sargasso Sea defined by surrounding ocean currents http://www.jimloy.com/biology/sargasso.gif

6. The “Seven” Seas • Before 15th Century: • Red Sea • Mediterranean Sea • Persian Gulf • Black Sea • Adriatic Sea • Caspian Sea • Indian Ocean • These were what was known, “sailing the 7 seas” • Current list also includes: • North Pacific • South Pacific • North Atlantic • South Atlantic • Indian • Arctic • Southern

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

8. History of Oceanography • http://www.divediscover.whoi.edu/history-ocean/index.html

9. Journey to the bottom of the ocean • Alexander the Great • Supposedly went down in sealed container in 332 BC • William Bebe - 1934 • Bathyshpere – heavy steel ball with windows • Went about 923m (3028 ft) • US Navy’s Trieste • took 3 people down 9906m (32,500 ft!) in Mariana Trench, heard cracking sound • Submersible Alvin • Began dives in 1964 • Can go down 4000m (13,120 ft) • Submersible Shinkai • Japanese submersible that can dive over 21,000ft • James Cameron – 2012 (National Geographic) • http://www.youtube.com/watch?v=DO6_jKN-1hw&feature=player_embedded

10. Nature of scientific inquiry • Natural phenomena governed by physical processes • Physical processes similar today as in the past • Scientists discover these processes • Make predictionsand test them • Leads to better understanding and prediction of future events that rely on natural processes

11. Scientific method • Observations and questions • Develop falsifiable, testable hypotheses • Science can only deal with hypotheses that are testable! • Predictions based on hypotheses • Test predictions • Comparative studies • Controlled manipulative experiments • Field and lab experiments • Lot of trial and error! And retesting! • Gather data and analyze results • Accept or reject (falsify) hypothesis • Modification of hypotheses

12. Scientific method Fig. 1.9

13. Scientific method • Theory • Well-substantiated by large body of data • Many facts, supported by testing of many scientists • “Probably true” versus “absolutely true” • Always possible that additional data cannot be fully explained by current theory • The public often thinks that scientists really don’t know because of the word “theory” • However, in biology the word theory is a close to a law as you will come! • Science is continually developing because of new observations and new technology

14. Formation of Solar System and Earth • Big Bang formed universe over 15 billion years ago • Earth formed from gases & dust • ~ 4.6 – 5 bya • How do we know that? Scientists use radiometric dating

15. Formation of Solar System and Earth • Nebular hypothesis • Nebula = cloud of gases & space dust • Mainly hydrogen and helium • Gravity concentrates material at center of cloud (Sun) • Protoplanets from smaller concentrations of matter (eddies)

16. Protoearth • Larger than Earth today • Homogeneous composition • Bombarded by meteorites • Moon formed from a chunk of protoearth after collision with large asteroid • Heat from solar radiation • Initial atmosphere boiled away • Ionized particles (solar wind) swept away nebular gases

17. Protoearth • Denser materials started to move to center • density stratification (layered Earth) http://instruct1.cit.cornell.edu/Courses/biog105/pages/demos/106/unit08/media/interior-of-earth.jpg

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

19. Chemical composition • Crust • Low-density, mainly silicate minerals • Oceanic and continental crust • Mantle • Mainly Fe (iron) and Mg (mangnesium) silicate minerals • Core • High-density, mainly Fe and Ni (nickel)

20. Physical properties • Lithosphere • Asthenosphere • Mesosphere • Outer core • Inner core • Rock 'behavior' determined by temperature, density and stress • ranges from brittle to plastic ("deformable") to elastic

21. Physical properties • Core • ~ 90% iron with nickel • 5,500-6,600O C (9900-12000O F) • Solid inner core and viscous liquid outer core • Differential spin of inner/outer cores  Earth's magnetism

22. Physical properties • Mantle • Iron and magnesium silicates • 2500O C (4500O F) • Inner mantle -mesosphere • rigid • 'Upper' mantle • Asthenosphere - partially molten  plastic • Lithosphere – rigid (part of crust)

23. Physical properties • Upper Mantle • Asthenosphere • Plastic – deforms by flowing • High viscosity – able to flow slowly • From 100 km to 700 km (430 miles)

24. Physical properties • Upper Mantle and Crust • Lithosphere • “Cool”, rigid, brittle • (500O C, 900O F) • Surface (“crust”) fused to uppermost mantle, to about 100 km (62 miles)

25. Two types of crust • Oceanic crust • Underlies ocean basins • Igneous rock basalt • Dark colored • Average thickness 8 km (5 miles) • Relatively higher density • 3.0 g/cm3 • Continental crust – thicker but LESS dense • Underlies continents • Igneous rock – granite • Average thickness 35 km (22 miles) • Lower density • 2.7 g/cm3

26. Isostatic adjustment (isostasy) • Buoyancy – less dense “floats” higher than more dense • Continental crust “floats” higher than oceanic crust on plastic asthenosphere • As we will see, when oceanic and continental crust meet, the oceanic crust is forced below the continental crust

27. Origin of Earth’s atmosphere • Partial melting resulted in out-gassingabout 4 billion years ago • Similar to gases emitted from volcanoes • Mainly water vapor (steam) • Carbon dioxide, hydrogen • Other gases such as methane and ammonia • Living organisms had dramatic effect

28. Origin of Earth’s oceans • Water vapor released by outgassing • Condensed as rain (acidic) • Accumulated in ocean basins • About 4 billion years ago • Ice Comets may have contributed to ocean waters, but much, much less than outgassing

29. Origin of Ocean Salinity • Rain dissolves rocks • Acidic due to CO2 and H2S gas levels in the atmosphere at that time • 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

30. Life in oceans • Life originated in the oceans • Originated as prokaryotic life • Ocean water gave protection against harmful UV rays from sun (ozone layer was not yet well established) • Earliest life forms fossilized bacteria in rocks about 3.5 billion years old • Found in marine rocks Fossil cyanobacteria, ~ 850 MYA http://www.ucmp.berkeley.edu/bacteria

31. Bacteria are microscopic organisms • How can scientists say they have found cyanobacteria fossils that are 3.5 billion years old? • Mats of cyanobacteria can form stromatolites • Trapped sediment and secreted calcium carbonate

32. Stanley Miller’s experiment – 1953 • Experiment replicated Earth’s early atmospheric conditions • They put molecules/gases that were present, water, exposed UV light, electrical sparks (atmosphere was very dynamic, lightening) • Organic molecules started to form by ultraviolet light, electrical spark (lightning), and mixture of water, carbon dioxide, hydrogen, methane, and ammonia • Organics combined to form more complex molecules • These molecules are needed for life http://fig.cox.miami.edu/~cmallery/150/life/Stanley_Miller_large.jpg

33. Evolution and natural selection – Darwin’s “On the Origin of Species” – 1859 • Populations of organisms adapt and change through time  evolve • Advantageous traits are naturally selected • Individuals with “better” traits for environment tend to survive and reproduce better than others • Advantageous traits passed on to offspring  inherited • Produces organisms that… • are adapted to environments • Organisms change environments

34. Types of life forms • Heterotrophs • Most bacteria and animals and fungi • Must get energy from others • Autotrophs • Chemosynthetic autotrophs • Bacteria that chemosynthesize, fairly recently discovered • Photosynthetic autotrophs • Photosynthetic bacteria, algae, and plants • Chlorophyll captures solar energy •  produces excess O2 as by-product released

35. Photosynthesis and respiration Fig. 1.19

36. Oxygen • Photosynthetic anaerobic bacteria released oxygen (O2) to atmosphere • About 2 billion years ago, sufficient O2 in atmosphere to oxidize (rust) rocks • Ozone (O3) built up in atmosphere • Protects Earth’s surface from ultraviolet solar radiation • Oxygen and ozone in atmosphere resulted in aerobic organisms to evolve and allowed life to move to land • Aerobic organisms (including us) need oxygen for cellular respiration

37. Age of Earth • Radiometric age dating • Spontaneous change/decay • Half-life • Can determine age of rocks and organisms • http://www.youtube.com/watch?v=2io5opwhQMQ • Earth is about 4.6 billion years old

38. Geologic time scale

39. MisconceptionsWhat have we learned that make these statements false? • Science is just a collection of facts just to be memorized. • Scientific ideas are absolute and unchanging. • Scientists have already studied all the Earth’s systems so there will not be any new discoveries. • All theories are permanent. • Science and technology can solve all of our problems. • Not everyone can love science and get something out of it. • Science always has exact answers. • All radioactivity is dangerous. • The Earth is younger than ~4.6 billion years old. • All rocks are more or less the same. • The Earth has always been pretty much the same it is now. • There is significant disagreement about Earth’s age among scientists. • Evolution has never been observed. • Evolution is a theory on the origin of life. • Life does not continually change. • Fossils are man made.