Oceanography Midterm Exam Study Guide –

 

Origin of Ocean, Plate Tectonics, and Seafloors

Chapters 1-4

I. Introduction to Oceanography – Chapter 1

          A. The Earth is a Dynamic Ever-changing System

                   1. Know the Earth's major subsystems

                  2. Be able to draw/ label the Earth's Cross-section

 

          B. Be able to define Oceanography.

          C. Oceanography and the Scientific Theory

                   1) Know the Scientific Theory approach to nature: the

 basic foundation of all sciences.

·        The basic steps

·        Hypotheses and Theories

·        Observations, Data and Evidence

·        Methods of Testing

·        Interpreting results

                   2) Understand the basics of how the approach works.

                   3) Find/create examples of the ST in the real world.          

                     

D. Be able to describe and explain the commonly-accepted

       explanations for the Origin of Galaxies, the Solar System,

        Earth, Ocean and Moon, and Life.

1) The Big-Bang hypothesis

2) The Solar nebula "cold" accretion hypothesis

3) Moltenization and differentiation periods of early Earth.

4) The origin and evolution of the Earth-Moon system.

5) The origin and evolution of Earth's early atmosphere,

oceans, and continental masses.

                   6) The origins of Life on Earth.

                   7) The “oxygen revolution”

 

          E. Know what makes the Earth such a dynamic planet!

                   1) Generation of INTERNAL HEAT from two key sources

·       Gravitational heat of accretion (core)

·       Radioactive isotopes barbeque (mantle)

                   2) The presence of LOTS OF WATER on the surface.

                   3) Amazing set of balanced physical, chemical, and energy

                             variables that allow water to exist in all three states.

                   5) SOLAR input.

                   6) Know and be able to describe the general physical and

                 chemical features of both, the Earth's interior and surface.

ü         The Earth's subsystems

ü         The global topographic and geographic surface

         patterns, e.g. layout of continental masses, 

      ocean basins, mountain ranges, trenches,

      island arcs, mid-ocean rift valleys, etc.

   

          F. Know what stimulated the voyages of the early seafaring

            civilizations – compare and contrast the

                   intent and purpose for voyaging of the:

                             1) Polynesians and Vikings

                             2) Phoenicians and Greeks

                             3) Chinese and Europeans

 

          G. List and describe the essential types of information

                found in a marine chart (map)

                             1) Longitude and latitude

                             2) Scale

                             3) Coastlines

                             4) Bathymetry (water depths and contours)

                              

          H. Describe the important oceanographic contributions

                   of the most influential people and organizations throughout the

               history oceanography

                             1) People like: Columbus, Megellan, Henry the

                                     Navigator, Darwin, C. Maury, Captain Cook, and

 John Harrison

2) Organizations within governments, military, and private/ 

        public research institutions

 

          I. List and Describe key technologic breakthroughs

that helped advance oceanographic research

                             1) Seaworthy ships

2) Compass

3) Sextant

4) Chronometer

5) Power winches

         6) Electronic sensing devices (ex: for salinity, currents)

7) Sonar

8) Satellite

9) GPS

10) Computers and data software

 

II. Plate Tectonics and the Seafloor – Chapter 2

          A. Know The Basics of the Earth's Rock Cycle -

1) What is it? The endless cycle of building-up and

     wearing down of the Earth's crust.

§        Building up by magmatism and crustal uplift.

§        Worn down by weathering and erosion.

§        Destroyed/recycled by subduction.

2) A complex physical and chemical interplay of

      processes between five major material reservoirs:

       magma, igneous rocks, sediments, sedimentary

       rocks, and metamorphic rocks.

3) Series of related geologic processes occur between

two material reservoirs:

 

                            4) Three Major Rock Types

ü     Each group defines a variety of rock types that have a common origin.

                                      1) Igneous Rocks - Formed by the cooling and

crystallization of either, magma deep beneath

the Earth's surface, or lava extruded on the

                   surface, or consolidation of volcanic ejecta.

           

2) Sedimentary Rocks - Formed from the deposited

                             layers of clastic and/or chemical sediment via

                             compaction and cementation.

 

                                       3) Metamorphic Rocks - Formed by metamorphic

                             reactions of pre-existing solid rock via a unique

                             combination of extreme heat, pressure, fluids, and

                              deviatoric stresses.

5. Major rock-forming Processes

a. Heating (any rock) Ž Partial Melting Ž Magma

b. Transport (magma) Ž Cooling Ž Crystallization Ž Igneous Rock

c. Weathering (any rock) Ž Erosion Ž Sediment

d. Deposition (sediment) Ž Compaction Ž Cementation Ž Sedimentary

      Rock  

e. Heating +/- Pressure +/- Fluids +/- Stress  Ž Metamorphic Rock

                     

                             6. Be Able to Draw A Simple Rock Cycle Diagram

 

 B. Know The Basics of Earth's Hydrologic Cycle

1) What is it?

·        The endless cycling of water via evaporation, precipitation, and runoff on Earth's surface.

·        Major player in controlling Earth's climate

·        Powers weathering and erosion.

·        Plays a key role in mid-ocean hydrothermal systems

·        Plays a key role in subduction zone.          

                             2. Be Able to Draw/Label A Simple Hydrologic Cycle Diagram

 

C.  Wegener's Theory of Continental Drift (TCD)

                   1) Be able to explain the overall basic concept of CD

                   2) Know the terms Pangaea, Gonwanaland, and Luarasia

                   3) List the major types of evidence supporting TCD

                   4) Know the major obstacle that discredited the TCD

                             5) Know the key scientists that developed/supported TCD

 

      D. Know All the Basics of the Plate Tectonic Theory --         

          1)  Stiff, outermost shell of solid Earth consisting of

                     the crust and uppermost mantle called the lithosphere

*      Broken up into 6 major plates & 12 minor plates –

*      Move over the hot, plastic athenosphere mantle.

2) Each tectonic plate moves independently: two adjacent

                   plates can interact in one of three ways:

*    Diverge

*    Converge

*      Slide past one another

 

3) Three types of plate boundaries and associated process

*      ·        Divergent = rifting/ seafloor spreading; tensional

*      ·        Convergent = subduction/ collision; compression

*      ·        Transform = strike-slip faulting; shearing

4) Spreading centers and Continental rifts form at divergent

                                      boundaries, where two plates are moving away from

                                      each other, forming brand-new oceanic crust.

 

          5) Subduction zones and magmatic arcs form at convergent

                             boundaries, where an oceanic plate dives beneath

                             either a continental or oceanic plate into the mantle.

6) Continental collision zones also form at convergent

           boundaries where two continental masses are

           meeting head-on.

7) Great, transform strike-slip fault systems are created

        where two plates slide sideways, past each other.

8) Three proposed driving mechanisms of plate tectonics

a.     mantle convection

b.   ridge push

c.    slab pull  

9) The plate interactions, over time, cause a

number of spectacular phenomena,  including magmatic arcs,

 mountain chains, terrane accretion and ocean basin collapses and

  openings.

·        Describe the terrane accretion process

·        Describe the Wilson Cycle  

                   10) The plate tectonic theory unifies the observation and hypotheses

                            which attempt to explain most geologic phenomena.

                   11) The Earth's rock cycle is driven in large part by  the perpetually moving plates

 

E. Seafloor Spreading (SS)

          1) Be able to explain the basic concept of seafloor spreading

          2) Know the key terms associated with seafloor spreading

          3) List the major types of evidence/discovers behind SS

          4) Know the key scientist that proposed

 

F. Subduction

          1) Be able to explain the basic concept of subduction

          2) Know the key terms related to subduction

          3) List the major evidence/discovers for subduction

          4) Know the key scientist that proposed

 

G. Important Points concerning Theory of Plate Tectonics - Know that:

                   1) Plate Tectonics is a unifying theory because it is able

                       to explain many geologic phenomena.

        2) The so-called "Wilson Cycle" represents a plate tectonic

     cycle of plate motions where an ocean basin is born,

    grows, then shrinks, and finally collapses.

       3) There are 500 million-year Supercontinent Cycles of plate

motions and interactions that begins with the break-up of

an old supercontinent and ends with the formation of a new

supercontinent.

              4) Plate tectonics is the cause of Earth's mountain building,

                     magmatism, and never-ending resurfacing of the planet.

     5) The Earth's rock cycle is fueled by plate tectonics.

           

 

      F. Be Able to Identify All Major Plate Tectonic Boundaries

                   On a Map or Globe

                   1) Circum-Pacific basin and adjoining continents

                   2) North and South Atlantic basin and adjoining continents

                   3) Indian Ocean and adjoining continents

 

      G. Be Able to Identify Elements of Plate Tectonics in a

                   Geographic Illustration (see online practice exam)

1) Match plate processes (ex. seafloor spreading)

                   with associated geographic features (ex. mid- ocean ridges)

 

H. Understand and be able to explain the concept of isostacy.

 

III. Marine Provinces  -- Chapter 3

A. Know the Geographic Significance of Seafloors

1) Oceans and seas cover over 70% of Earth's surface

2) Earth's seafloors constitute a global-scale topographic

       region of low-lying relief that contrasts to the high-

      standing relief of the continents

3) Seafloors represent the most vast (by far) depositional

       environment on Earth

·  Site of massive sedimentation and region of sedimentary

    rock production

4) The evidence used to establish and support the Theory

      of Plate Tectonics was established from the scientific

       study of seafloors and its sediments

 

B. Know Components and Nature of Continental Margins

·        Shelf – flat portion nearest shoreline

·        Slope – steep outer edge of shelf

·        Rise – base of slope where continebt and oceanic crust meet

           1) Shelf-slope break, Submarine canyons, Turbidity currents

          2) Continental margin seafloors consist mainly of

                              Granitic crust = outer edges of continents

                               Covered primarily by Terriginous sediments

3) Water depths are shallow; up to 200 meters on shelves

          4) Explain difference between Passive versus Active

                       continental margins

C. Know Components and Nature of Deep Ocean Basins

§        Abyssal plains and hills

§        Oceanic trenches

§        Oceanic ridge systems and fracture zones

§        Hydrothermal vents

§        Oceanic islands, atolls, guyouts, and seamounts

1) Ocean basns have rugged, variable topography

2) Oceanic basin seafloors consist of

·        Basaltic crust = ophiolite package

·        Pelagic clays and oozes (sediments)

·         Pelagic clays derived from continents

·         Oozes consist mainly of skeletons of microscopic marine organisms

 3) Water depth of deep ocean average 4,000 meters

 

IV. Seafloor Sediments - Chapter 4

D. List and Describe the Types of Seafloor Sediments

          1) Four types of marine-based sediment - See Table 5.2

·        Lithogeneous

·        Biogenous

·        Hydrogeneous

·        Cosmogenous

2) Pelagic clays derived from primarily three land-based

       sources

·        Rivers

·        Volcanic eruption (ash falls)

·        Windblown material

·        Consist mainly of quartz and clay

3) Describe the two main types of Biogenous Oozes

·       Calcium carbonate oozes

·        Siliceous oozes

·        Constitute fecal pellets from larger animals

·        Fine sand- to silt-size particles

4) Define the sources of calcium carbonate oozes

·        Foraminifera

·        Cocoliths

·        Found on bottoms less than 4,500 meters deep (CCCD)

5) Define the sources of siliceous oozes

·       Tropical Radiolarians

·        Polar Diatoms

6) Define types of hydrogenous sediments

·        Manganese nodules

·       Phosphate nodules

·       Massive metal sulfide deposits

·        Evaporites

 

E. Describe and Explain the Distribution of Seafloor

      Sediments -

          1) Study Table 5.3 very carefully

2)  Study Figure 5.13 very carefully

3) Distribution of each sediment type controlled by several

              environmental factors:

·               Proximity to sediment source

·        Rate of sedimentation (each specific sediment type)

·        Chemical stability at site of deposition

4) Unique distribution pattern for each sediment type

          Study Distribution Map shown in Figure 5.13

·        Lithogeneous -

·        Biogenous

·        Hydrogeneous

·        Cosmogenous

 

F. Define the Rates of Seafloor Sedimentation

          1) Deep ocean sedimentation rates are very low

2) Each type of deep seafloor sediment has specific rate

·        Lithogeneous -  2 millimeters per 1000 years

·        Biogenous - 1 to 6 centimeters per 1000 years

·        Hydrogeneous - 1 to 10 millimeters per 1 million years

·        Cosmogenous - Negligible

 

G. List and Describe Methods of Seafloor Sediment

       Sampling

·        Piston Coring samplers

·        Drag bucket and Clamshell samplers

 

      H.  List and Describe Types of Seafloor Mineral Resources

          1) Continental Margins

§       Oil and gas (hydrocarbons)

§       Sand and Gravel

2) Deep Ocean basins

·       Manganese nodules

·       Massive metal-sulphide deposits

·        NO gold and silver

 

V. Vocabulary Lists - Chapters 1-4

A. Study the Terms and Concepts Lists Found at the End

     of Each Chapter

          1) Attempt to remember them

          2) Be ready to define many of these (at least the

            ones that I have included in this study guide)

 

Seawater Properties, Atmosphere and Ocean Circulation

Chapters 6-9

   You will need to be able to answer the following questions in order to correctly answer the multiple choice and matching questions on the midterm exam.  Some questions (as noted) can be answered most easily with a drawing or diagram. Be sure to LABEL the important parts of your diagram.  Drawing and labeling diagrams and creating “concept maps” are very effective means of remembering and understanding information, particularly science material.  Terms highlighted in red are extra important to know

1.    What is salinity? How is it measured?

2.    List the two ions with the highest concentrations in seawater. Indicate which ion is a cation and which is an anion. Which salt consists of a combination of these two ions (spell out the name, not just the chemical formula)?

3.    Explain what oceanographers mean when they say that a dissolved ion or salt is conservative in seawater.

4.    Give an explanation for the observation, based on evaporite composition, that sea salt concentration and composition have been nearly constant for about the last 1 billion years.

5.    Why are oxygen concentrations higher in ocean surface waters and lower in the deep ocean?

6.    Why are carbon dioxide concentrations lower in ocean surface waters and higher in the deep ocean?

7.    What are nutrients? Give the names of two nutrients and briefly describe their importance in the ocean.

8.    The energy that the Earth receives from the sun is returned to space by two processes, reflection and re-radiation. Describe, briefly, what happens to the sun's energy when it is reflected and when it is re-radiated.

9.    In the heat budget of the Earth, which two things must balance (or be equal to one another)? What would be the consequence if this balance did not exist?

10.  Why are the equatorial regions of the Earth, on average, hotter than the polar regions?

11.  How does evaporation of water from the oceans result in a transfer of heat to the atmosphere?

12.   Why is carbon dioxide called a "greenhouse gas"?

13.   Why is the concentration of carbon dioxide in the Earth's atmosphere increasing?

14.   It is difficult for scientists to predict how much the Earth's climate will warm, if the concentration of carbon dioxide in the Earth's atmosphere doubles over the next 50 years. Describe one of the reasons for this difficulty.

15.   Why is the salinity of ocean water greater near 30° N than it is near 60° N latitude?

16.   List two processes that increase the salinity of seawater, and two processes that decrease the salinity of seawater.

17.   List two properties of water that affect water density, and, for each, indicate whether density would increase or decrease if that property increased.

18.   Define the terms thermocline and halocline, and pycnocline.

19.   What condition exists when a water column is unstable? Briefly describe one way in which a water column can become unstable.

20.   Define thermohaline circulation.

21.   In which regions of the ocean do deep and bottom waters form? Why is the formation of deep and bottom waters confined to these regions?

22.   A hypothesis has been proposed that states there is a link between the climate of northern North America and Europe (especially ice ages) and the rate of formation of North Atlantic Deep Water. How could North Atlantic Deep Water formation rates affect climate?

23.  Oceanographers say that the deep and bottom waters of the North Pacific Ocean are "old". Why are these waters said to be old?

24.  Define the term water mass.

25.  Explain why a parcel of air which was originally moving directly northward from the equator is displaced to the east, so that it travels to the northeast of its original position. (Note that it is not sufficient to name the effect responsible (Coriolis effect); you must explain what causes this effect (Coriolis effect)).

26.   Unusually large amounts of rainfall occur near the equator. Why?

27.   Between the equator and 30° N, the winds generally blow from the northeast (the Northeast Trade Winds). How do atmospheric convection and the Earth's rotation produce this wind pattern? A diagram may be helpful in answering this question.

28.   Between 30°S and 60°S latitude, the winds generally blow from the northwest (the Westerlies; this wind band includes the "Roaring Forties" and "Furious Fifties" of sailors' lore). How do atmospheric convection and the Earth's rotation produce this wind pattern? A diagram may be helpful in answering this question.

29.   Why is low atmospheric pressure generally found over the oceans of the Northern Hemisphere in winter?

30.   Why do winds in the Northern Hemisphere generally blow counterclockwise around low pressure areas? A diagram may be helpful in answering this question.

31.   What causes the wet, or summer, monsoon found along the west coast of India ? How is this related to the onshore breeze that often occurs in coastal areas during the afternoon?

32.   Although El Nińo was first noted along the west coast of South America , it is actually a global phenomenon. What are 3 unusual ocean or weather conditions associated with El Nińo, either in the eastern tropical Pacific or elsewhere?

33.   Why do hurricanes form only in the tropics?

34.   What is the Ekman Spiral? How is it related to Ekman Transport? (A diagram may be helpful in answering this question.)

35.   How does Ekman Transport cause coastal upwelling? (A diagram may be helpful in answering this question.)

36.   What is an ocean gyre?

37.   What are eddies? How do they form?

38.   Define the terms divergence, convergence, upwelling, and downwelling.

39.  Describe how the divergence and convergence of ocean currents can cause upwelling and downwelling, respectively. 

       40.   Describe how prevailing winds blowing parallel to a coastline can cause either, upwelling and downwelling.  

       41.  Define thermohaline circulation, and its role in ocean circulation.

      42. List the five common water masses found in the temperate and tropical latitudes.   

      43. Illustrate a general temperature-salinity (T-S) diagram, and show how different sets of T-S values for different water masses can have identical    densities.

      44. Name, describe, and elaborate on the origin and activity of the three major deep-water masses.

45.   Describe and illustrate the classic model of pure thermohaline circulation.

      46.  What is the process of “caballing”?

     47.  What is the vast global-scale ocean circulation system current system termed the “global conveyor belt for heat transport”?

48.    What are the two traditional types of methods for measuring currents?

49.  Which type of current measuring method works best for each type of water mass?

50.  What is “acoustical tomography”, and what is its usefulness in studying ocean currents?

 

Essay Questions - A super effective means of “getting down” the science terms and concepts is to answer questions in essay form (usually require answers of about 10 sentences in length).  The following are key questions concerning the material covered for this midterm exam:  

1. Describe the Earth’s heat budget. It is not necessary to give a quantitative answer, but your answer should include a description of the major processes affecting the sun’s energy after it enters the Earth’s atmosphere. How will increasing carbon dioxide concentrations in the Earth’s atmosphere affect the Earth’s heat budget? Indicate the specific processes affected as well as the overall effect on the budget.

2.  Describe the changes in water density in the upper ocean layer over the annual cycles at tropical, temperate, and polar latitudes and the corresponding changes in water temperature. Indicate at which times of year, in each region, that the water column is unstable and mixing with underlying water occurs. Diagrams may make this easier.

   3  Describe the circulation of the Atlantic Ocean below 1000 m depth. Discuss the sites of formation of water masses, how they form (e.g., cooling at the ocean surface, mixing of other water masses), and their paths of flow. Include the following water masses in your answer: North Atlantic Deep Water (NADW), Antarctic Intermediate Water (AAIW), Antarctic Bottom Water (AABW), and Mediterranean Water (MW).

4.    From 0° to 30° N latitude, the Northeast trade winds blow from the northeast; between 30° and 60° N latitude, the Westerlies blow from the southwest. Explain how this  wind pattern, in along with the Earth’s rotation (Coriolis effect), causes the clockwise flow of currents circling the North Pacific Ocean , the North Pacific Gyre.

5.  Define and discuss in adequate detail the vast global-scale ocean circulation system current system termed the “global conveyor belt for heat transport”.   Also discuss how it has primary importance in moderating and shaping Earth’s climate