Introduction to Oceanography 112 - MName: Introduction to Oceanography 112 - M. Yasuda ... Every night, remarkable numbers of living things rise towards the surface of the ocean across

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Name: Introduction to Oceanography 112 - M. Yasuda

Assignment 3 – Shape of the Earth’s surface, internal layering, and plate tectonics

Due date: March 14, 2019 Quiz 4: April 21, 2019

IN THE NEWS

Part A. Naval bases dealing with sea level rise Read

https://news.nationalgeographic.com/2017/02/pentagon-fights-climate-change-sea-level-rise-defense-department-military/

Purposes:

• Reading comprehension – what did the article actually say?

• Recalling and/or being able to find basic knowledge that is referenced in the article and seeing how it relates to the subject at hand

• Learning about a topic related to Oceanography that impacts the world around us today

• Learning about a topic on your own, without going over it in lecture 1. The Defense Department wants to: a. Repair problems at bases related to sea level change that are already taking place b. Plan and prepare for costs associated with sea level rise in the future c. Keep bases in working condition for their intended purposes 2. The Defense Department has had difficulty getting money to fix and upgrade bases because:

a. Money is hard to come by and people have different priorities on how to spend it b. The House of Representatives does not want to spend money on issues related to climate

change, unlike the Senate c. No one is willing to put in a request to Congress

3. In what state is the coastal city of Norfolk located? ____________________________

4. How many times a year does the base at Norfolk flood currently? _______________ 5. If no upgrades are made, how many times a year is the base at Norfolk projected to flood by the year

2100? _______________ 6. What event currently causes the days of flooding at the base at Norfolk? _______________

7. At what level of government does the U.S. Congress exist? a. National b. State c. Regional or local 8. What are the two parts of the U.S. Congress? a. House of Senators b. House of Representatives c. Senate d. Executive branch e. Department of Defense 9. Who chooses representatives to the House of Representatives (Congress) and the Senate?

a. The President b. Voters c. State Governors

____________________________________________________________

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Part B. The diel vertical migration Every night, remarkable numbers of living things rise towards the surface of the ocean across the globe. Each sunrise, this mass of life descends back into the depths of the ocean, into a part of the ocean called the twilight zone. This pattern of motion is called the diel vertical migration (DVM) and it is the Earth’s largest migration. The term diel refers to processes that occur on a daily basis. The organisms that take part in the DVM consist of living things that cannot make their own food and includes a category of living things called zooplankton, and larger animals such as squid and lanternfishes. Living things that make their own food by photosynthesis don’t participate in the DVM because they are obligated to remain in sunny waters near the surface of the ocean during the day. The surface dwellers that do not participate in the DVM include living things categorized as phytoplankton (plankton that are able to photosynthesizer), larger seaweeds, and the very few true plants that live in the ocean. The DVM lifestyle plays a significant role in Earth’s carbon cycle. When phytoplankton consume and extract carbon dioxide out of seawater near the ocean’s sunlit surface, it makes room for more carbon dioxide molecules to enter seawater from the overlying air, helping to reduce and regulate the concentration of carbon dioxide in the atmosphere. However, when phytoplankton die and decompose, organic matter is converted back into original forms which include carbon dioxide and it escapes back into the atmosphere. Thus, just encouraging more photosynthesis in the ocean won’t necessarily result in a net reduction in atmospheric carbon dioxide. However, if an animal comes up to the surface at night and eats phytoplankton, it removes the carbon dioxide that was consumed by phytoplankton from surface waters. The predator takes the body of the prey it hasn’t fully digested and carries it into deeper water, away from the surface by each sunrise. If that animal respires or poops in the deep, rather than while it’s at the surface, it results in the eventual release of carbon dioxide in deep waters. But this time, it’s down too far from the air-sea interface and the carbon dioxide doesn’t can’t easily escape to the atmosphere. So, the DVM animals may be important in sequestering (moving and trapping) carbon dioxide in the deep ocean, making more room for surface seawater to take up atmospheric carbon dioxide at the surface. That process helps to reduce atmospheric carbon dioxide. How significant is this effect in numbers? That’s a matter for researchers to determine and it’s one of the many details of a complex system that need to be understood in order to predict future climate.

Is there a downside to pushing carbon dioxide into seawater? Yes – increased carbon dioxide in seawater can make the seawater slightly more acidic and have a large negative impact of marine life. Ocean acidification is a topic we’ll cover later. For now, learn how sonar helped to discover the Deep Scattering Layer.

Read/skim the following articles:

Deep Scattering Layer

http://www.coexploration.org/bbsr/classroombats/html/vertical_migration.html

Deep Scattering Layer

https://en.wikipedia.org/wiki/Deep_scattering_layer

Diel Vertical Migration (The word diel is pronounced “die·eel” like a mean order given to eels.)

http://funwithkrill.blogspot.com/2011/08/diel-vertical-migration-dvm.html

Plankton - Phytoplankton and Zooplankton

https://www.whoi.edu/science/B/people/kamaral/plankton.html

Note: Remember - if you come across a term you’re not sure about, look it up online or in your textbook.

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10. The event known as the diel vertical migration takes place: a. Every day b. Some days c. Every fall d. Every spring e. Annually f. During El Niño 11. What is the term we use for events that take place yearly a. Daily b. Monthly c. Annual d. Diel 12. What are phytoplankton? a. Members of the plankton community that are capable of photosynthesis (like plants) b. Members of the plankton community that are not capable of photosynthesis (like animals) c. Tend to be smaller organisms that are poor swimmers that require light for photosynthesis d. Any marine organism that tend to be poor swimmers

13. By definition, what are plankton? Choose the single best answer. a. Organisms that tend to be small, live in the water column, and/or unable to swim effectively in a

direction of their choosing so that they move with the motion of water

b. Organisms that live on or in the seafloor that are not able to swim very well

c. Organisms that swim very well d. Organisms that live at boundary between air and sea and move with the motion of water e. Organisms that are a certain size, being very small 14. What are zooplankton? a. Members of the plankton community that are capable of photosynthesis b. Members of the plankton community that are not capable of photosynthesis c. Any marine organism that requires light for photosynthesis 15. Where do phytoplankton live? a. In the upper sunlit part of the ocean (the photic zone) b. Below the upper sunlit part of the ocean (below the photic zone) c. Mostly below the photic zone during the day d. Mostly below the photic zone at night 16. Where do larger animals and zooplankton tend to live in marine environments? a. In the photic zone b. Above the photic zone during the day c. Below the photic zone during the day d. Closer to the sea surface at night 17. What characteristics are true about the deep scattering layer (DSL)? a. It is a concentration of life closer to the surface of the ocean during the day b. It is a concentration of life in deeper waters during the night c. It is a layer composed of animals (non-photosynthesizers) and zooplankton d. It is a layer composed of phytoplankton

See a photo of the density of fish in the DSL. The most common fish in this layer is the lanternfish or myctophid fish. You can see these fish in the photo because they are bioluminescent.

Aggregation of lanternfish

http://www.photolib.noaa.gov/htmls/nur00004.htm

18. What observations led to the discovery of the deep scattering layer and diel vertical migration?

a. Satellite observations

b. A false sonar reflector that disappeared during the night

c. Whale songs 19. Which term refers to a process rather than a thing?

a. Deep Scattering Layer b. Diel Vertical Migration

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20. Why might larger animals and zooplankton engage in the diel vertical migration?

a. To feed without being so easily seen by predators b. To be able to see prey c. To capture sunlight for photosynthesis d. To escape the pressure of deep water

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Part C. Sonar and living things

Sonar is the primary method used to determine the depth to the seafloor, whether the specific method involves

a single-point echo sounder or a multibeam system. Sonar stands for Sound Navigation and Ranging. The sonar or echolocation method works by measuring the time it takes for sound waves to bounce off surfaces and return to a receiver usually set near the sound source. The sonar equipment is usually carried or installed on a ship, although it can also be towed or deployed in other ways. In a basic sense, sonar equipment consists of a sound source, sound receiver, and a clock that measures two- way travel time. As we discussed in class, it is the two-way travel time that gives us information about distance, when the velocity of sound in seawater is known. It is deployed where distances to objects and surfaces cannot be measured directly. The method can be used to determine the distance of objects in water in any direction, not just the vertical direction. In class, we used an approximate velocity of 1,500 m/s, for the speed of sound in seawater. For detailed work, slight differences and variations in the speed of sound in seawater are determined in order to estimate distances more accurately. But sound velocity in seawater doesn’t vary that much, so our approximation gives us a reasonable and “ballpark” estimate of distance. A sound wave is a type of acoustic or mechanical wave. Unlike light or electromagnetic waves, mechanical waves require an intervening medium in order to transmit. An intervening medium consists of matter, usually consisting of different types of atoms and molecules at high-enough density. Spacing of one atom every mile isn’t dense enough to transmit sound. Sound waves cannot transmit or move across outer space, where atoms and molecules are space so far apart to be nearly non-existent. In class, we’ll discuss how mechanical waves move through rock (earthquake waves), water (sonar and animal echo-location), and air (sound as we hear it). Early depth measurements were done at single locations by “pinging” the seafloor with sound. Over time, improvements in technology and recording allowed moving ships to collect data along a line or track, instead of single points. Today, multibeam sonar systems collect data in a swath (strip with width) along a ship’s track, covering greater area than a thinner line. Multibeam systems allow bathymetric data to be collected faster, by requiring fewer crossings over an area for coverage. You might envision a multibeam system set on a lawn mower – the wider the mower, the fewer passes needed to cover an area. Mathematically and computationally, this required great technical improvements over the last few decades, to sort out all of the simultaneous echoes that return from a swath of seafloor at any one time. We simplified the echo diagram in class greatly. When sound exits the sound source, a half-sphere of sound goes out and bounces off the seafloor in many places. An echo returns from everywhere the sphere of sound touched, creating a continuous and simultaneous cloud of echoes back to the receiver on a moving ship. (We also learned about satellite altimetry which is also echo-based, but uses the “echo” of electromagnetic radiation rather than sound.) Animals such as bats, dolphins, and some humans have the capacity to use echolocation for navigation and hunting.

Resources

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Dolphin echolocation

https://seaworld.org/en/animal-info/animal-infobooks/bottlenose-dolphins/communication-

and- echolocation Human echolocation

https://en.wikipedia.org/wiki/Human_echolocati

on

FYI- The boy who sees without eyes

https://www.youtube.com/watch?v=TeFRkAYb1uk

20. What part of a dolphin’s head focuses outbound sound?

a. Blowhole b. Brain c. Melon d. Lower jaw 21. What part of a dolphin’s head receives and guides the returning echo?

a. Blowhole b. Brain c. Melon d. Lower jaw

22. How deep is the seafloor where sonar measures a two-way travel time of 10 seconds? This question is intended to be done by mental math. No calculation.

23. If you read a two-way travel time of 45s, you should:

a. Calculate distance to the seafloor b. Check your calculation c. Check that you read the two-way travel time correctly

24. Which area has the deepest seafloor?

a. Place where the two-way travel time is 6s b. Place where the two-way travel time is 5 s c. Place where water depth is 1,500 meters below sea level

25. What is the average depth of the seafloor?

a. 150 mbsl b. 2,700 mbsl c. 4,000 mbsl d. 11,000 mbsl 26. Modern sonar equipment can measure depth continuously, while the ship carrying the sonar equipment is

moving. a. True b. False

27. We looked at several cross-sections (side views, profiles) of the seafloor that were produced by plotting

data collected by sonar. Consult the diagram on the practice sonar problem for reference. These cross- sections show: a. The shape of the seafloor in side view, along the path of the ship b. The shape of the seafloor in side view, along a straight-line path c. The shape of the seafloor in side view, but not necessarily along a straight-line path

28. On the diagram referenced in the previous question, if the y-axis is given in units of two-way travel

time, where is the sea surface or sea level?

a. At the top of the diagram given b. At two-way travel time = 0 seconds

c. At the top of the printed page d. Not necessarily on the diagram 29. Which kind of wave travels further in seawater?

a. Sound b. Light

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30. Sound waves tend to bounce off surfaces when they encounter different material, such as a change from water to sediment, or from one rock type to another. a. True b. False

31. You can already see the shape of the seafloor, on a cross-section that plots two-way travel time rather

than depth, because two-way travel time is directly related to depth. a. True b. False

____________________________________________________________ PLATE TECTONICS

Suggested reading in textbook

Chapter 3 – Earth Structure and Plate Tectonics Chapter 4 – Ocean Basins Chapter 1 - Pages 3-8 – Scientific Method

Additional reading that may be useful to you 1. Online – This Dynamic Earth: The Story of Plate Tectonics – another presentation

http://pubs.usgs.gov/gip/dynamic/dynamic.html

2. Plate tectonics

http://en.wikipedia.org/wiki/Plate_tectonics

Key diagrams

1. Some of the animations I showed in class

http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/t_tectonics.html Not all the links connect back to this page. So if you get lost go back in from the link above.

2. Crustal Age

http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/images/WorldCrustalAge.jpg

3. Age of rocks found at the surface of the Earth around the globe

http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/images/crustalage_lg.jpg

4. Map of lithospheric plates (tectonic plates) – Flash animation with interactive layers Includes overlays for surface relief, volcanism, earthquakes, and crustal age http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/p_map_plate_layers.html

5. Map of lithospheric plates (tectonic plates) – Static (less info, but visible on iPad)

http://pubs.usgs.gov/gip/dynamic/slabs.html

6. Plate reconstruction movie

http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/p_plate_reconstruction_blakey.html

7. Map of global surface (National Geographic – Heezen and Tharp) Pages 414-415 in textbook

8. Map of global surface – ETOPO1

https://www.ngdc.noaa.gov/mgg/image/color_etopo1_ice_low.jpg

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Vocabulary list for plate tectonics 1. Crust, mantle and core 2. Planetary differentiation 3. Density stratification (layering) 4. Buoyancy 5. Isostatic equilibrium 6. Lithosphere 7. Asthenosphere 8. Cross-section 9. Aerial view 10. Topography 11. Bathymetry 12. Geotherm 13. Convection 14. Radioactive decay 15. Gravitational compression 16. Seafloor spreading 17. Mid-ocean ridges

18. Transform faults 19. Fracture zones 20. Subduction and subduction zone 21. Trench 22. Island arc 23. Volcanic arc 24. Divergent, convergent and transform plate margins 25. Active and passive continental margins 26. Lithospheric plate 27. Tectonics 28. Plate tectonics 29. Hotspot or mantle plume 30. Paleomagnetic anomaly or stripe 31. Paleomagnetic reversal

Part D. Continent vs. Ocean

A geologist’s definition of a continent is different than the everyday definition. In everyday language, the “continent” of North America extends from its Pacific to Atlantic shorelines. This is not the definition used by a geologist. A geologist considers a continent to be an area of the Earth’s surface that is composed of continental rock (i.e. continental crust) underneath the relatively thin layer of surface sediments. Oceanic areas are distinguished from continents by being underlain by material composed of oceanic rock (i.e. oceanic crust) below surface sediments. For our purposes, the distinction between continent and ocean isn’t based on being covered with water or not, but by the type of igneous rock that makes up the outermost layer of the Earth at a particular location. The rock of the oceanic crust happens to lie lower than continental crust, making the Earth’s surface water pond preferentially over areas underlain by oceanic crust rather than continental crust. Oceanic crust lies lower than continental rock because of the way the thinner and more dense oceanic crust sits on top of the underlying mantle, with its top lying lower than continental rock.. The true lateral (sides in horizontal) edges of the continents extend beyond the margins of shorelines to the seaward edges of submerged continental shelves. Continental margins are usually located somewhere underneath and near continental shelf breaks. During times of past glaciation, sea level was lower and continental shelves were exposed. 32. Where is the western edge of the continent of North America near San Diego?

a. At the shoreline b. At the San Andreas Fault c. At the Patton Escarpment

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33. 33.1. Mark and label the location of the continental margin on the map of the southern California Borderland given below. It is the same map we studied in class. Make labels on the sides of the map and use arrows to point to relevant parts where they touch the side of the map.

33.2. Mark and label the Patton Escarpment.

Map of California Borderland. Map courtesy C. Goldfinger and J. Chaytor, OSU. Image used with permission.

34. The image to the right shows a section of the ETOPO1 map.

It shows the eastern margin of North America that faces the Atlantic Ocean.

34.1. Mark the eastern edge of the continent of

North America on this map. The geology of the area is complex so we will not discuss whether the Blake Plateau is technically continental or oceanic. For this purpose, assume that the Blake Plateau is composed of continental crust.

Reference: https://en.wikipedia.org/wiki/Blake_Plateau 34.2. Label Cape Hatteras on the map to the right. 34.3. Label Bermuda on the map to the right. 34.4. Label Chesapeake Bay on the map to the right.

Observe and consult the ETOPO1 map as needed to answer questions.

You may want to bookmark this map because we will refer to it often.

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https://www.ngdc.noaa.gov/mgg/image/color_etopo1_ice_low.jpg

35. In map view, which sides of the continents of North America, South America, Europe, and Africa tend to

have wider continental shelves? Choose the single best answer.

a. Eastern b. Western

c. Facing the Pacific d. Facing the Atlantic

36. Observe this map which shows the global distribution of areas of continental and oceanic crust.

https://en.wikipedia.org/wiki/Crust_(geology)#/media/File:World_geologic_provinces.jpg

36.1. Based on what you know about the distribution of continental and oceanic crust, areas of oceanic crust on this map are assigned: Choose the single best answer. a. Shades of blue b. Shades of warm colors – pink, red, orange, yellow, and purple c. Shades of blue (except for one shade of blue that is used for continental crust)

36.2. What sets the age of an igneous rock?

a. Time elapsed since the rock arrive on the planet b. Time elapsed since that rock was deposited in the ocean c. Time elapsed since that rock solidified from a previously molten form

36.3. Unlike the continental areas, the areas of oceanic crust:

a. Are made up of older crust b. Exhibit an orderly age pattern c. Exhibit an orderly and symmetrical age pattern that is centered on mid-ocean ridges

36.4. The oldest parts of the oceanic crust occur:

a. At mid-ocean ridges b. Furthest away from mid-ocean ridges 36.5. Seawater sits preferentially on:

a. Oceanic crust b. Continental crust c. Neither type of crust 36.6. Oceanic crust is composed of: a. A rock type similar to granite B. A dark-colored rock

c. A rock type that is almost always basalt d. A light-colored rock

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Part E. Internal layers of the Earth We know that the inside of the Earth is layered, although it wasn’t layered in its earliest days. We know that layering exists based on evidence provided by earthquakes (mechanical waves that pass through rock).

Your task is to learn about the two ways the Earth’s internal layering is divided and classified, based on:

One way: By differences in the composition of different layers AND Another way: By differences in the mechanical properties of different layers These two criteria result in the two different systems of naming layers inside the Earth. These two systems have different layer names and the boundaries between layers do not necessarily occur at the same depths in the two systems.

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37. Which layers form the outermost part of the Earth? a. Crust b. Mantle c. Core d. Lithosphere e. Asthenosphere f. Mesosphere g. Inner core h. Outer core 38. Which layer defines the part of the earth we classify as continental? a. Crust b. Mantle c. Core d. Lithosphere e. Asthenosphere f. Mesosphere g. Inner core h. Outer core

39. Which layer defines the part of the earth we classify as a tectonic plate?

a. Crust b. Mantle c. Core d. Lithosphere e. Asthenosphere f. Mesosphere g. Inner core h. Outer core

40. The rock type at the lowest part of the lithosphere is different from the rock type at the topmost part of the underlying asthenosphere. This statement is:

a. True b. False 41. Each part of the Earth’s interior can be assigned two different layer names.

a. True b. False

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Part F. Crust vs. lithosphere 42. Below any sediment cover that happens to fall onto the seafloor, what kind of material makes up the

seafloor? a. Continental crust b. Oceanic crust c. Basalt d. Andesite or Granite

44. How does oceanic crust differ from continental crust? a. Continental crust is thinner than oceanic crust b. The base of continental crust sits lower into the underlying mantle c. The average rock type is different d. The density of continental crust is greater than oceanic crust

45. The terms “crust” and “lithosphere” are synonyms (i.e. mean the same thing) a. True b. False

46. Which layer constitutes (makes up) the entire vertical thickness of each moving plate?

a. Crust b. Lithosphere 47. Which boundary is generally associated with coastlines rather than tectonic hazards?

a. Continental margin b. Plate margin 48. What distinguishes the lithosphere from the underlying asthenosphere?

a. Responding to stress in a different way b. Being made up of a different type of rock 49. In the context of the previous question, what does the term ”distinguish” mean?

a. To tell apart b. To be well known for an accomplishment c. To be ancient 50. Massive areas of rock in the lithosphere can bend without breaking when:

a. Great pressure is applied rapidly b. Great pressure is applied slowly c. Earthquakes occur

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51. What is the average thickness of a lithospheric plate? a. 5-7 km b. 100 m c. 100 km d. 6,371 km

52. What is the average thickness of oceanic crust?

a. 5-7 km b. 100 m c. 100 km d. 6,371 km e. Thicker than the lithosphere f. Thinner than the lithosphere

53. The thickness of the lithosphere at mid-ocean ridges is:

a. Less than 100 km b. 100 m c. 100 km d. 6,371 km 54. Where is the western margin of the South American Plate? a. Peru-Chile Trench b. Mid-Atlantic Ridge c. East Pacific Rise 55. Where is the eastern margin of the continent of South America? a. East coast shoreline b. Continental shelf break off the east coast c. Mid-Atlantic Ridge 56. A single plate: a. Is made up of one type of crust b. Is often made up of both oceanic and continental crust c. Moves as a single cohesive unit in one general direction on a large scale

57. The North American Plate is the same thing as the continent of North America. a. True b. False

58. Very roughly the North American Plate is bounded by: a. West coast of North America b. East coast of North America c. East Pacific rise d. Mid-Atlantic Ridge

59. Which part of a plate undergoes the greatest change over time, growing in area or disappearing entirely by subduction? a. Continental b. Oceanic

60. What is the typical depth of the continental shelf break?

61. Continental shelf areas are:

a. Parts of continental crust b. Parts of oceanic crust 62. What is the average depth of the ocean?

____________________________________________________________ Part G - Key process of plate tectonics #1: Seafloor spreading

Note: There are two major processes of plate tectonics – seafloor spreading and subduction. Make sure you know about these processes. If a question on an exam asks about the key processes of plate tectonics, it is asking about either seafloor spreading or subduction.

63. Seafloor spreading takes place at: a. Trenches b. Mid-ocean ridges c. Hawaii d. San Andreas Fault

64. Seafloor spreading:

a. Produces and adds new areas of continental crust to the Earth’s surface b. Produces and adds new areas of oceanic crust to the Earth’s surface c. Destroys seafloor

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d. Changes the shape of the seafloor and is related to the motion of attached continents e. Produces new oceanic crust

65. In overall area, the Atlantic is now:

a. Growing larger b. Shrinking and closing c. Staying constant in size 66. The first appearance of the Atlantic Ocean began with rifting (opening) within a continent, in a way that may be similar to activity along the East African Rift today. The Atlantic began opening: a. ~18,000 years ago, about the same time as the last major glaciation b. ~180-200 million years ago, during the Jurassic Period (of dinosaur fame) c. ~2.4 billion years ago, when Earth’s atmosphere started to become oxygenated Consult: Opening of the North Atlantic – Reconstruction by scientists Chris Scotese https://www.youtube.com/watch?v=l6EIC83xcQk

Geologic time scale https://en.wikipedia.org/wiki/Geologic_time_scale

67. Earth is about 4.5 billion years old. Suppose the Earth’s lithosphere has existed for the last 3 billion years

and behaved the way that it does today. Suppose too, that each major opening and closing of the Earth’s oceans takes 300 million years, how many times could the Earth have experienced major openings, closings, and disappearances of oceans throughout its history?

a. ~1 b. ~10 c. ~100 d. ~1000 68. Many oceans have opened up in previously continuous land masses over the long history of the Earth.

Those oceans no longer exist. What has happened to the oceanic crust that made up the floor of those oceans over 180 million years ago?

a. Attached to continents b. Recycled back into the interior of the Earth c. In the Pacific Ocean d. Buried under sediment 69. Continents have been around the Earth’s surface for a long time, for billions of years, but the entire

seafloor is relatively very young. How old is the oldest remaining oceanic crust in the Atlantic and Pacific Oceans?

a. ~4.4 billion years b. ~2.1 billion years c. ~180-200 million years d. ~18,000 years 70. How old is the oldest remaining continental crust in the continents, found on its surface? a. ~4 billion years b. ~2 billion years c. ~180-200 million years d. ~18,000 years

71. The oceanic crust at or near the crest of a mid-ocean ridge is: a. Relatively new b. Relatively old c. About zero years old 72. In map view, the age pattern of oceanic crust is symmetrical on each side of every mid-ocean ridge, and the pattern runs parallel to the length of each mid-ocean ridge. a. True b. False

73. The oceanic crust on opposites sides of a mid-ocean ridge are always on different plates because: a. They move in different directions b. Subduction takes place there c. It is volcanic d. It is a hotspot or mantle plume 74. As the northernmost segment of the East Pacific Rise (in the Gulf or California or Sea of Cortez) spreads, what is it doing to the Pacific Plate that lies west of the San Andreas Fault, including San Diego? a. Making it move to the northwest b. Making it move to the southeast

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75. Which ocean(s) are producing new seafloor today? a. Pacific b. Atlantic 76. Which ocean(s) are losing area (shrinking) now? a. Pacific b. Atlantic

77. What is the depth at the tops of most mid-ocean ridges? a. About 4,000 mbsl b. About 11 kmbsl c. About 3,000 mbsl d. The shallowest in the open ocean over oceanic crust (not including areas of continental shelf- slope-rise and islands ) 78. What material erupts out of mid-ocean ridges? a. Andesite b. Basalt c. Lava d. Magma 79. The molten rock that flows out of a mid-ocean ridge originates: a. Just under the crest of mid-ocean ridges at a relatively shallow depths, from magma bodies within otherwise solid rock b. In the outer core, the only totally molten layer of the Earth c. Underneath each mid-ocean ridge segment where melting is concentrated by tensional forces that reduce pressure in that region d. May be associated with the spacing of convection cells located in the underlying mantle 80. The continent of North America and the western half of the North Atlantic Ocean are parts of the same plate that move together as a single unit. a. True b. False 81. The continent of North America and the eastern half of the North Pacific are part of the same plate that move together as a single unit. a. True b. False 82. Beyond the continental shelf-slope-rise in the seaward direction, the seafloor is generally shallowest at: a. The area just beyond the continental rise b. Halfway between the continental rise and mid-ocean ridge

c. At mid-ocean ridges

83. The broad depth pattern of the oceans is a prominent feature of the shape of our planet. In a direction perpendicular to mid-ocean ridges, what is the broad depth pattern across oceans?

a. Seafloor slopes downward away from mid-ocean ridges, deepest close to continental margins b. Seafloor slopes downward away from mid-ocean ridges, shallowest close to continental margins c. Seafloor slopes upward away from mid-ocean ridges, shallowest close to continental margins

84. The mid-ocean ridge is elevated: a. Because underlying rock is relatively warm, compared with oceanic crust to each side b. Because underlying rock is relatively cold, compared with oceanic crust to each side 85. As oceanic crust cools over the millions of years and moves away from mid-ocean ridges, it:

a. Expands, causing the seafloor depth to change from ~6,000 mbsl to ~2,700 mbsl over ~180 million years b. Contracts, causing the seafloor depth to change from ~2,700 mbsl to ~6,000 mbsl over ~180 million years

86. In the vertical, if a 100 km thickness of lithosphere shrinks by 3 km over 180 million years, by what

percentage has it contracted? a. 1% b. 3% c. 10% d. 30% e. 60%

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Part H - Key process of plate tectonics #2: Subduction

87. Which features are associated with subduction? a. Mid-ocean ridge b. Trench c. Accretionary prism or accretionary wedge d. Fracture zone e. Transform fault f. Volcanic arc g. Island arc 88. At what depths do most earthquakes originate within Earth? a. Within the lithosphere b. Within the upper 100 km c. Within totally molten rock d. Within partially molten rock 89. Subduction zones are notable because earthquakes occur at progressively deeper and unusually great

depths under continents, compared with other settings. a. True b. False 90. What is the source of magma in a volcanic arc or island arc? a. The molten outer core b. Hotspot under the lithosphere c. Partial melting of a subducting plate d. Below the subducting plate 91. What causes the subducting plate to melt? a. Being forced into a situation that is warmer than it was previously b. Encountering lower pressure caused by tension (pull apart forces) c. Encountering lower pressure caused by compaction (pushing together forces) 92. What general hazards are caused by the process of subduction? a. Tsunami b. Earthquakes c. Volcanic eruption 93. Which of these hazards does not generally occur due to forces along transform plate margins? a. Tsunami b. Earthquakes c. Volcanic eruption 94. Where are most transform plate margins located?

a. Land b. Ocean

95. The rim of this ocean is called the “Ring of Fire” due to the presence of stratovolcanoes. a. Pacific b. Atlantic c. Indian 96. Which ocean is nearly entirely surrounded by trenches and thus subduction zones and related hazards? a. Pacific b. Atlantic c. Indian 97. Continental margins that are near subduction zones and any other type of plate margin are: a. Active continental margins b. Passive continental margins 98. Which side of the continent of North America is a passive continental margin? a. West b. East 99. Which side of the continent of North America is less prone to tectonic hazards? a. Active b. Passive 100. Large mountain ranges on the planet, whether on land or undersea, are produced by: a. Subduction b. Seafloor spreading c. Transfom faults d. Continent-continent convergence e. Ocean-ocean divergence

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101. The mountain ranges that form over subduction zones: a. Are formed of continental crust that has been crumpled due to plate collision b. Are embedded with volcanoes that release the products of partial melting of subducting plates c. Are crumpled due to collision, but do not include volcanoes d. Can include layers of sedimentary rock that have been uplifted to great heights above where they were formed

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Part I – Plate vs. continental plate margins 102. Which terms are associated with plate margins? a. Convergent b. Active c. Divergent d. Passive e. Transform 103. What features are located at or near ocean-to-continent convergent plate margins? a. San Andreas Fault b. Trenches c. Transform faults

d. Mid-ocean ridges e. Volcanic arcs f. Island arcs g. Hawaiian-Emperor Seamount chain h. Himalayas i. Appalachians

104. What features were formed at or near continent-to-continent convergent plate margins? a. San Andreas Fault b. Trenches c. Transform faults

d. Mid-ocean ridges e. Volcanic arcs f. Island arcs g. Hawaiian-Emperor Seamount chain h. Himalayas i. Appalachians 105. Give an example of a real place that is a: 105.1. Continent-continent divergence zone _________________________________ 105.2. Ocean-ocean convergence zone _________________________________ 105.3. Continent-continent convergence zone _________________________________ 106. The Appalachian Mountains are an example of: a. Modern continent-continent convergence b. Modern continent-ocean convergence c. Past continent-continent convergence d. Past continent-ocean convergence Appalachian Mountains https://en.wikipedia.org/wiki/Appalachian_Mountains

107. Where are the Appalachian Mountains located? a. Mostly in the U.S. b. Western North America c. Eastern North America d. Southwest 108. What features are located at or near ocean-ocean divergent plate margins? a. San Andreas Fault b. Trenches c. Transform faults d. Mid-ocean ridges e. Volcanic arcs f. Island arcs g. Fracture zones h. Hawaiian-Emperor Seamount chain i. Himalayas j. Appalachians

109. Which side of North America is an example of a passive continental margin? a. West b. East

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110. What is the difference between a passive and active continental margin? a. Passive continental margin is the edge of a continent that happens to be at or near a plate margin b. Passive continental margin is the edge of a plate that happens to be at or near a plate margin c. Passive continental margin is the edge of a continent that is far from a plate margin and located within the interior of a plate

111. What type of plate margins are associated with the greatest tectonic hazards – earthquakes, volcanoes, and tsunami? a. Passive b. Active c. Divergent d. Convergent e. Transform

112. Which kind of continental margin has a wider continental shelf? a. Active b. Passive c. Those around the Pacific d. Those around the Atlantic 113. Why do the world’s largest rivers tend to exit passive margins rather than active margins? a. Large mountains keep rivers from flowing out to the sea on passive margins b. Mountains such as the Andes keep rivers from flowing to the sea on passive margins c. Subduction produces large obstructions to the flow of rivers d. Large mountain ranges that obstruct rivers do not tend to form on passive margins 114. The continent of North America is rimmed by: a. Passive margins b. Active margins

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Part J - The Hawaiian-Emperor Seamount Chain

115. The islands and seamounts of the Hawaiian-Emperor Seamount Chain may have formed over: a. A convergent plate margin b. An active plate margin c. A hotspot underneath the lithosphere d. A hotspot inside the lithosphere

e. A mid-plate location f. A mid-ocean ridge g. An asteroid impact site

116. Which of these chains of volcanoes is (are) age-progressive? a. Hawaiian-Emperor Seamount Chain b. Volcanoes in the Andes c. Volcanoes along the Mid-Atlantic Ridge 117. The oldest feature of the Hawaiian-Emperor Seamount Chain is: a. The seamount closest to the Aleutian Trench b. The Big Island of Hawaii c. The bend in the seamount chain d. Loihi 118. If you have a plate moving southward over a hotspot, in which direction will the oldest volcanoes lie? a. North b. South c. East d. West 119. A hotspot is thought to be in a relatively fixed position underneath an overlying plate. a. True b. False 120. The older seamounts are more submerged because: Choose the single best answer. a. They are continually eroded by waves as they age b. The seafloor on which they sit continually sinks as it ages c. Sea level is rising 121. Which of these statements are true?

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a. Most of the seafloor was produced at mid-ocean ridges, at an initial depth of about 2,700 mbsl b. Most seafloor becomes progressively deeper as it gets older c. The seafloor is relatively shallow at mid-ocean ridges relative to locations to either side d. By the time seafloor has moved from the East Pacific Rise to the area of the Hawaiian hotspot, seafloor is relatively deep

122. Which statements are true about volcanoes that make up the Hawaiian-Emperor Seamount Chain? a. They are mostly composed of basalt b. Eruptions are more hazardous than volcanoes at subduction zones c. Their lava is more viscous than at Mt. St. Helens d. The piles of lava that make up each seamount are shorter in overall height than volcanoes in the Andes e. The overall shape of the seamounts is shield shaped rather than cone-shaped 123. Which material has exited to the surface of the Earth? a. Lava b. Magma FYI: Read about the next seamount on the way - Loihi

https://en.wikipedia.org/wiki/L%C5%8D%CA%BBihi_Seamount

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Part K. Plate tectonics as a theory

Read Tectonism http://www.lpi.usra.edu/education/explore/shaping_the_planets/tectonism.shtml Consult this and your lecture notes Plate tectonics https://en.wikipedia.org/wiki/Plate_tectonics

Plate tectonics is one of the major revolutionary scientific theories advanced by humans.

See examples here: Top 10 revolutionary scientific theories https://www.sciencenews.org/blog/context/top-10-revolutionary-scientific-theories 10 most famous scientific theories that were later debunked http://www.famousscientists.org/10-most-famous-scientific-theories-that-were-later-debunked/ Some of these were never elevated to theory status in the first place, and were actually hypotheses. FYI - Example of a concept in oceanography that did not turn out to be true: Excerpt from Wikipedia

“Bathybius haeckelii was a substance that British biologist Thomas Henry Huxley discovered and initially believed to be a

form of primordial matter, a source of all organic life. He later admitted his mistake when it proved to be just the product of a

chemical process (precipitation).

In 1868 Huxley studied an old sample of mud from the Atlantic seafloor taken in 1857. When he first examined it, he had

found only protozoan cells and placed the sample into a jar of alcohol to preserve it. Now he noticed that the sample contained

an albuminous [like egg white] slime that appeared to be criss-crossed with veins.

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Huxley thought he had discovered a new organic substance and named it Bathybius haeckelii, in honor of German biologist

Ernst Haeckel. Haeckel had theorized about Urschleim ("primordial slime"), a protoplasm from which all life had originated.

Huxley thought Bathybius could be that protoplasm, a missing link (in modern terms) between inorganic matter and organic

life.

Huxley published a description of Bathybius and also wrote to Haeckel to tell him about it. Haeckel was impressed and

flattered and procured a sample for himself. In the next edition of his textbook The History of Creation Haeckel suggested that

the substance was constantly coming into being at the bottom of the sea. Huxley did not agree but speculated that Bathybius

formed a continuous mat of living protoplasm that covered the whole ocean floor.

Other scientists were less enthusiastic. Charles Wyville Thomson examined some samples in 1869 and regarded them as

analogous to mycelium [thready, root-like structures of fungi]. George Charles Wallich claimed that Bathybius was a product

of chemical disintegration.

In 1872 the Challenger expedition began; it spent three years studying the oceans. The expedition also took soundings at 361

ocean stations. They did not find any sign of Bathybius, regardless of the claim that it was a nearly universal substance.

In 1875 ship's chemist John Young Buchanan analyzed a substance that looked like Bathybius from an earlier collected

sample. He noticed that it was a precipitate [solid chemical substance that forms in a liquid] of calcium sulfate from the

seawater that had reacted with the preservative liquid (alcohol). Buchanan suspected that all the Bathybius samples had been

prepared the same way and notified Thomson, the leader of the expedition. Thomson sent a polite letter to Huxley and told

about the discovery.

Huxley realized that he had been too eager and made a mistake. He published part of the letter in Nature [a scientific journal]

and recanted his previous views. Later, during the 1879 meeting of the British Association for the Advancement of Science, he

stated that he was ultimately responsible for spreading the theory and convincing others. Most biologists accepted this

acknowledgement of error.”

124. Plate tectonics is:

a. A plate b. The motion of plates c. The motion of continents

d. Sea floor spreading e. A hypothesis f. Continental drift

g. A revolutionary scientific theory

Note: The term revolutionary is somewhat subjective, but the theories cited below are nearly universally considered to have been revolutionary.

Heliocentrism – that the Earth orbits the Sun, not the other way around as previously thought Evolution - that living things are descended from other living things, with traits being passed between

individuals and species by DNA, not by spontaneous generation as previously hypothesized Plate tectonics - that the Earth’s surface is broken up into plates that move around significantly, as a

result of seafloor spreading and subduction, not quite according to concepts of continental drift as previously hypothesized 125. What characteristics contribute to a scientific theory being revolutionary?

a. A scientific theory explains many things that have been observed and is broad in its relevance b. A scientific theory lets us predict a lot of things that will happen in the future c. It is a breakthrough concept that leads to rapid acquisition of new knowledge, technology, and/or

solutions to long-standing problems d. It affects how we think about a lot of things, including our world view and how we see ourselves in the context of the broader universe e. It is sometimes a major shift in how we think the natural world works

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126. Science is: Choose the single best answer. a. A thing: The factual knowledge we have come to know b. An action: The process of producing new knowledge by a specific method c. A thing: The machinery that lets us make new discoveries 127. Knowledge, such as that which we have learned about in class: a. Is the product of science b. Is science in action c. Is useful in making decisions about daily and long-term activities d. Is the foundation upon which we can invent new technologies and make new discoveries e. Is often a valuable commodity

128. Relative to its usage in everyday context, in the context of science, the term “theory”: a. Has the same meaning b. Refers to a concept that is much more certain c. Refers to a concept that is much less certain 129. Every piece of knowledge in science is: a. Subject to the test of new observations as time goes by b. A permanent stepping stone to new scientific knowledge c. Is the best current stepping stone to new scientific knowledge d. Is the best current knowledge upon which to make scientific predictions of future events e. Collected by the scientific method f. Is observable and reproducible g. Not equal in value or certainty 130. The scientific method is confined to the natural world, i.e. all that is observable. a. True b. False 131. The hypothesis about Bathybius haecklii concerned: a. The origin of matching coastlines across the Atlantic Ocean b. The transition from non-living to living matter c. The depth pattern of the ocean

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Part L - The significance of discovering paleomagnetic stripes in the seafloor

Part I – Magnets and the Earth’s magnetic field

Additional resources, to read as much as you need: Magnets Earth’s magnetic field http://en.wikipedia.org/wiki/Magnet http://en.wikipedia.org/wiki/Earth's_magnetic_field

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The Earth behaves as if there were a very large bar magnet embedded in its interior. You might imagine a magnet, just like the image of the bar magnet to the right, to be located in the Earth’s core, with the long direction of the magnet aligned roughly along the Earth’s rotational axis (running N to S).

The Earth’s internal magnet exerts a magnetic field that

affects substances, such as little bits of iron, which are susceptible to magnetic fields. The magnetic field is a force field that extends beyond the edges of the magnet itself. The field is generated by the motion of iron in the Earth’s outer core.

If you sprinkle iron filings (powdered iron) around a bar

magnet, as shown in the image on the previous page, each little piece of iron lines up along invisible field lines around the magnet, revealing the pattern of the field. Any susceptible mineral that forms in the Earth’s magnetic field also lines up in this way. The floating needle in a compass aligns along invisible field lines.

Each little iron filing has a “North” pole end and a “South” pole end. Pieces of iron exhibit a condition called

polarity and within a single piece, they possess areas that have opposite poles of polarity (the north and south, or positive and negative poles).

When two objects that possess magnetic polarity approach each other, opposite poles of each object attract and

similar poles repel each other. Remember that in magnetism, opposites attract. Thus, a compass needle points North because compass needles are made of magnetic material that is attracted to

the Earth’s “North” pole. Technically, the polarity near the Earth’s north rotational pole is south-magnetized, in terms of magnetics.

The magnetic field is not the same as the gravitational field. Both fields attract things, but each field only affects

objects that possess certain characteristics. The magnetic field operates on objects that have magnetic polarity while the gravitational field operates on the mass of an object. Also, the magnetic field has two opposite poles per object, while the gravitational field has a single center of mass per object, making the shapes of the magnetic and gravitational fields very different.

In general, the term polarity refers to having two opposite properties on different parts of a single entity, such as a

magnet or a molecule (note – electrons and protons are not polar entities). A pole is one of the two places on a magnetic object where the magnetic field is most concentrated, such as at the

North magnetic pole and the South magnetic pole. A field is the region of space over which a given effect, such as a magnetic force field exists.

132. What kinds of materials are attracted to magnets? If you’re not sure, find a magnet and test it out.

a. Metal paper clip b. Plastic cup c. Silver d. Water 133. If you place a tiny bar magnet (the size of an iron filing), close enough to a larger bar magnet, it will: a. Rotate around until the tiny bar magnet lines up along a field line b. Rotate around until the North pole side of the tiny bar magnet points towards the South pole side of the bigger magnet c. Rotate around until the North pole side of the tiny bar magnet points towards the North pole side of the bigger magnet

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134. Since there is no actual bar magnet inside the Earth, what is the source of the Earth’s magnetic field? a. The solid inner core b. The liquid outer core c. Mantle

d. The asthenosphere e. Oceanic crust f. Continental crust 135. Resource: https://science.nasa.gov/science-news/science-at-nasa/2003/29dec_magneticfield Is the Earth’s North magnetic pole located at the North rotational pole? a. Yes b. No c. Close by, but not exactly at the same place 136. Does the Earth’s magnetic pole stay in the same location over time? a. Yes b. No

137. We encounter objects made up of iron in our everyday lives, but most of those objects do not exert magnetic forces. What key condition allows the iron in the outer core to generate a magnetic field?

a. Being mixed with nickel b. Being molten and in motion

138. What could cause the Earth’s magnetic field to disappear or cease? a. Melting of the inner core b. Cooling of the planet and solidification of the outer core c. Cooling of the planet and solidification of the asthenosphere d. Subduction of oceanic crust 139. A geomagnetic reversal is: a. A time when the magnetic field increases b. The magnetic field near the Earth’s north rotational pole assumes the polarity that used to be near the south rotational pole c. The Earth physically flips over in the north-south direction, reversing the location of the polar areas 140. The current magnetic polarity condition is called: a. Normal b. Reversed 141. When did the Earth’s magnetic field last reverse? ______________________ Consult this resource that summarizes what is known about past geomagnetic reversals: https://en.wikipedia.org/wiki/Geomagnetic_reversal

142. Which conditions made life possible on the surface of the early Earth? a. The existence of oxygen in the Earth’s early atmosphere b. The existence of water on the Earth c. The existence of a protective magnetic field 143. How old is the Earth, i.e. how long has it existed? _____________________________

All done!