CSS Geography Oceanography Syllabus

Oceanography syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Oceanography in CSS Geography, not a summary of it.

1. 1

   Ocean Basins and Their Properties

   3 topics

   • Origin of oceans and seas
   • Characteristic features of ocean basins
   • Bottom topography of Atlantic, Indian and Pacific Oceans
2. 2

   Physical Properties of Ocean Water

   3 topics

   • Temperature distribution: causes and effects
   • Salinity distribution: causes and effects
   • Heat and salt budgets
3. 3

   Ocean Deposits and Circulation

   3 topics

   • Ocean floor deposits and classification
   • Ocean circulation
   • Waves, currents and tides
4. 4

   Marine Resources and Issues

   4 topics

   • Biotic, mineral and energy resources
   • Coral reefs and coral bleaching
   • Sea-level changes
   • Law of the sea and marine pollution

Oceanography flashcards for CSS Geography

25 of 53 cards from the Oceanography deck — real questions with worked answers.

1. What two broad theories explain the origin of the oceans' water, and which is dominant?

   Degassing (volcanic outgassing of water vapour from Earth's interior, then condensation) is the dominant theory; a secondary contribution comes from extraterrestrial sources (comets/icy meteorites). Most ocean water is now attributed to degassing of the early Earth.

2. According to continental drift / plate tectonics, how did the present oceans originate?

   The supercontinent Pangaea broke up (~200 million years ago) and the fragments drifted apart; seafloor spreading filled the widening gaps, forming the Atlantic, Indian and other modern ocean basins.

3. What are the four major relief divisions of the ocean floor?

   Continental shelf, continental slope, continental rise (deep-sea fan), and the abyssal plain (deep ocean floor), along with deeps/trenches.

4. Define the continental shelf and give its typical depth and average gradient.

   The gently sloping, submerged margin of a continent extending from the shoreline to the shelf break, generally to about 200 m depth, with a very low gradient (roughly 1° or less).

5. Define the continental slope and its characteristic gradient.

   The relatively steep zone (about 2°–5°, locally much steeper) descending from the shelf break (~200 m) down to the deep-ocean floor, marking the true edge of the continental block.

6. What is the continental rise?

   A gently sloping wedge of accumulated sediment at the base of the continental slope, formed by turbidity currents and deposition, that grades into the abyssal plain.

7. What are abyssal plains?

   Extremely flat, sediment-covered regions of the deep-ocean floor, typically 3,000–6,000 m deep, among the flattest and smoothest areas on Earth.

8. What is a mid-oceanic ridge and how is it formed?

   A continuous submarine mountain chain along divergent plate boundaries where seafloor spreading occurs; rising magma creates new oceanic crust, building the longest mountain system on Earth.

9. What is an oceanic trench (deep) and where is the deepest point?

   A long, narrow, very deep depression formed at subduction zones; the deepest is the Challenger Deep in the Mariana Trench (Pacific), about 11,000 m (~10,994 m) deep.

10. What is a seamount and how does it differ from a guyot?

    A seamount is an isolated submarine volcanic peak rising over 1,000 m above the seafloor but not reaching the surface; a guyot is a flat-topped seamount whose top was planed by wave erosion before subsiding.

11. Describe the dominant bottom topography feature of the Atlantic Ocean.

    The S-shaped Mid-Atlantic Ridge running roughly north–south down the centre, dividing the basin into eastern and western troughs; the Atlantic is relatively shallow with broad continental shelves and few deep trenches.

12. What characterizes the bottom topography of the Pacific Ocean?

    The largest and deepest ocean, ringed by deep trenches and active volcanic/subduction zones (the 'Ring of Fire'), with the East Pacific Rise, numerous seamounts, guyots and coral islands; it contains the deepest point on Earth.

13. What is distinctive about the Indian Ocean's floor topography?

    An inverted-Y / 'M'-shaped system of ridges (Mid-Indian, Carlsberg and Southwest/Southeast Indian Ridges) radiating from a central node; relatively few trenches except the Sunda (Java) Trench; broad shelves near the Indian subcontinent.

14. Name the major source of heat for the ocean surface and the main controls on sea-surface temperature (SST).

    Insolation (solar radiation) is the main heat source. Controls on SST include latitude, prevailing winds, ocean currents, depth, and the amount of cloud/evaporation.

15. How does ocean surface temperature vary with latitude?

    It generally decreases from the equator toward the poles; highest SSTs (~26–30°C) occur in equatorial/tropical waters and fall to near or below 0°C at the poles.

16. What is the thermocline?

    The transition layer of the ocean where temperature decreases rapidly with depth, lying between the warm, well-mixed surface layer and the cold deep layer.

17. Why is the diurnal and annual range of ocean surface temperature small compared with land?

    Water has a high specific heat, is mobile (mixing distributes heat), is transparent (heat penetrates and is spread over depth), and loses heat through evaporation—so it heats and cools slowly.

18. How do ocean currents affect the temperature distribution of surface waters?

    Warm currents raise the temperature of the waters and adjacent coasts they flow toward (e.g., Gulf Stream), while cold currents lower temperatures (e.g., Labrador, Benguela); they redistribute heat poleward.

19. Define salinity of seawater and state the average open-ocean value.

    Salinity is the total mass of dissolved salts in grams per kilogram (per mille, ‰) of seawater. The average ocean salinity is about 35‰ (35 g/kg, ~3.5%).

20. What are the main factors that increase ocean surface salinity?

    High evaporation, low precipitation, little freshwater inflow, and limited mixing—conditions typical of enclosed subtropical seas.

21. What factors decrease ocean surface salinity?

    High precipitation, large river/freshwater inflow, melting of ice, and low evaporation.

22. Why is salinity highest in the subtropics (around 20°–30° latitude) rather than at the equator?

    The subtropics have high evaporation and low rainfall under descending dry air, raising salinity; the equator has heavy rainfall and high humidity that dilute surface waters.

23. Which water body has the highest salinity, and roughly what value?

    Among open seas, the Red Sea is very high (~40‰); enclosed water bodies are higher still—the Dead Sea reaches around 240‰ and the Great Salt Lake even more (these are lakes, not open ocean).

24. What are the two most abundant ions in seawater, and roughly what proportion of dissolved salts do they form?

    Chloride (Cl⁻) and sodium (Na⁺); together as sodium chloride they make up about 85% of the dissolved salts in seawater.

25. What is the principle of 'constancy of composition' (Forchhammer's/Marcet's principle) for seawater?

    Although total salinity varies from place to place, the relative proportions of the major dissolved ions remain almost constant throughout the world ocean.

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