1. The Ocean Floor Mapping the Ocean Floor Continental Margins Geological Oceanography

2. Objectives: at the end of the period, you are expected to: 1. Define what is Oceanography, 2. Value the importance of the ocean, 3. label the features of the ocean floor.

3. Oceanography -an interdisciplinary science that draws on the methods and knowledge of geology, chemistry, physics, and biology to study all aspects of the world ocean. Geological Oceanography

4. Geography of the ocean The area of the Earth is 510 M km 2. Of this total, approximately 360 M km 2 is represented by oceans and marginal seas. Geological Oceanography

5. Marginal seas are the seas around the ocean’s margin Geological Oceanography

6. Northern Hemisphere (land sphere) Geological Oceanography  61% water  39% land

7. Southern Hemisphere (water sphere) Geological Oceanography  81% water  19% land

8. Oceans of the World 1. Pacific Ocean 2. Atlantic Ocean 3. Indian Ocean 4. Southern Ocean 5. Arctic Ocean Geological Oceanography

9. Pacific Ocean covers more than 166 million square kilometers about 1/3 of the Earth surface Geological Oceanography

10. Atlantic Ocean covers an area of 82 million sq km Geological Oceanography

11. Indian Ocean covers an area of about 73 million sq km Geological Oceanography

12. Southern Ocean large circumpolar body of water totally encircling the continent of Antarctica Geological Oceanography

13. Arctic Ocean the smallest ocean - more than five times smaller than the Indian and Atlantic oceans Geological Oceanography

14. Bathymetry - is the measurement of ocean depths and the charting of the shape or topography of the ocean floor. Techniques in bathymetry : 1. SONAR (Sound Navigation and Ranging) or echo sounder 2. Multi-beam SONAR 3. Satellite altimetry Geological Oceanography

15. Echo sounding is a method of measuring depth using powerful sound pulses. The time it takes for the sound pulse to travel to the sea bed and bounce back is a measure of the depth. Geological Oceanography

16. The speed of sound in water is 1500 m/s. Thus, depth of any part of an ocean is given by: d= ½ (1500 m/s X echo travel time) Geological Oceanography

17. Multibeam systems can provide more accurate measurements than echo sounders. Multibeam systems collect data from as many as 121 beams to measure the contours of the ocean floor. Geological Oceanography

18. Satellite altimetry is an indirect way of measuring depth and detecting sea floor features. Satellites measure the sea surface height from their orbits by bouncing rapid pulses of radar energy off the ocean surface. Geological Oceanography

19. This extra mass pulls the sea surface into gentle “hills” above the features. Thus we can “see” features below the surface by measuring the variations in sea surface height that these features cause! Geological Oceanography

20. 1. Continental margin 2. Ocean basin floor 3. Mid-ocean ridge Geological Oceanography Three Major Provinces

21. Geological Oceanography Continental Margin Active Continental Margin Passive Continental Margin 1.Continental shelf 2.Continental slope 3.Continental rise

22. Continental Margin is the transition to the deep ocean basin. The margin belongs mostly to the continent. Geological Oceanography

23. 1. Passive margins (Atlantic-type margins) face the edges of diverging tectonic plates. Because there is no collision or subduction taking place, tectonic activity is minimal and the Earth's weathering and erosional processes are winning. Continental Margins Geological Oceanography

24. CONTINENTAL SHELF - the shallowest portion of the margin and the portion nearest to the continent. This feature is simply an underwater extension of the adjacent above-water portion of the continent, the COASTAL PLAIN.

25. CONTINENTAL SLOPE- is the sloping edge of the continent as it merges into the deep ocean basin. Geological Oceanography

26. Submarine Canyons known as deep, steep-side valleys. Geological Oceanography

27. Turbidity Currents Turbidity currents are periodic down slope movements of dense, sediment- laden water. Geological Oceanography

28. CONTINENTAL RISE- is a wedge of sediment that has accumulated at the base of the slope due to the change in gradient from the steeper slope to the virtually flat abyssal plain. Geological Oceanography

29. Passive Continental Margin

30. 2. Active margins (Pacific-type margins) are located near the edges of converging plates, where one plate dives beneath another at an oceanic trench, in the process of subduction. Active margins are therefore sites of extensive volcanic and earthquake activity. Geological Oceanography Continental Margins

31. Geological Oceanography Passive Continental Margin Active Continental Margin The active margin has subduction at an oceanic trench occurring next to it. The passive margin faces the diverging plate boundary of the mid- ocean ridge.

32. Geological Oceanography