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 • 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.

40. Ocean Literacy Principles • 1.a - The ocean is the dominant physical feature on our planet Earth—covering approximately 70% of the planet’s surface. There is one ocean with many ocean basins, such as the North Pacific, South Pacific, North Atlantic, South Atlantic, Indian and Arctic. • 1.b - An ocean basin’s size, shape and features (islands, trenches, mid-ocean ridges, rift valleys) vary due to the movement of Earth’s lithospheric plates. Earth’s highest peaks, deepest valleys and flattest vast plains are all in the ocean. • 1.h - Although the ocean is large, it is finite and resources are limited. • 5.a - Ocean life ranges in size from the smallest virus to the largest animal that has lived on Earth, the blue whale. • 5.e - The ocean is three-dimensional, offering vast living space and diverse habitats from the surface through the water column to the seafloor. Most of the living space on Earth is in the ocean.

41. Sunshine State Standards • SC.6.N.1.2 - Explain why scientific investigations should be replicable. • SC.6.N.1.5 - Recognize that science involves creativity, not just in designing experiments, but also in creating explanations that fit evidence. • SC.6.N.2.2 - Explain that scientific knowledge is durable because it is open to change as new evidence or interpretations are encountered. • SC.6.N.2.3 - Recognize that scientists who make contributions to scientific knowledge come from all kinds of backgrounds and possess varied talents, interests, and goals. • SC.6.N.3.1 - Recognize and explain that a scientific theory is a well-supported and widely accepted explanation of nature and is not simply a claim posed by an individual. Thus, the use of the term theory in science is very different than how it is used in everyday life. • SC.6.E.7.9 - Describe how the composition and structure of the atmosphere protects life and insulates the planet. • SC.7.N.1.5 - Describe the methods used in the pursuit of a scientific explanation as seen in different fields of science such as biology, geology, and physics. • SC.7.N.1.7 - Explain that scientific knowledge is the result of a great deal of debate and confirmation within the science community. • SC.7.E.6.1 - Describe the layers of the solid Earth, including the lithosphere, the hot convecting mantle, and the dense metallic liquid and solid cores. • SC.7.E.6.4 - Explain and give examples of how physical evidence supports scientific theories that Earth has evolved over geologic time due to natural processes. • SC.7.E.6.5 - Explore the scientific theory of plate tectonics by describing how the movement of Earth's crustal plates causes both slow and rapid changes in Earth's surface, including volcanic eruptions, earthquakes, and mountain building. • SC.8.N.1.3 - Use phrases such as "results support" or "fail to support" in science, understanding that science does not offer conclusive 'proof' of a knowledge claim. • SC.8.N.1.4 - Explain how hypotheses are valuable if they lead to further investigations, even if they turn out not to be supported by the data. • SC.8.N.3.2 - Explain why theories may be modified but are rarely discarded.

42. Sunshine State Standards (cont) • SC.912.N.1.3 Recognize that the strength or usefulness of a scientific claim is evaluated through scientific argumentation, which depends on critical and logical thinking, and the active consideration of alternative scientific explanations to explain the data presented. • SC.912.N.1.7 Recognize the role of creativity in constructing scientific questions, methods and explanations. • SC.912.N.2.2 Identify which questions can be answered through science and which questions are outside the boundaries of scientific investigation, such as questions addressed by other ways of knowing, such as art, philosophy, and religion. • SC.912.N.2.4 Explain that scientific knowledge is both durable and robust and open to change. Scientific knowledge can change because it is often examined and re-examined by new investigations and scientific argumentation. Because of these frequent examinations, scientific knowledge becomes stronger, leading to its durability. • SC.912.N.3.1 Explain that a scientific theory is the culmination of many scientific investigations drawing together all the current evidence concerning a substantial range of phenomena; thus, a scientific theory represents the most powerful explanation scientists have to offer. • SC.912.E.5.1 Cite evidence used to develop and verify the scientific theory of the Big Bang (also known as the Big Bang Theory) of the origin of the universe. • SC.912.E.5.5 Explain the formation of planetary systems based on our knowledge of our Solar System and apply this knowledge to newly discovered planetary systems. • SC.912.E.6.1 Describe and differentiate the layers of Earth and the interactions among them. • SC.912.E.6.3 Analyze the scientific theory of plate tectonics and identify related major processes and features as a result of moving plates. • SC.912.E.6.5 Describe the geologic development of the present day oceans and identify commonly found features.