1. The Global Ocean
The Vast World Ocean

2. Objectives What is oceanography?
What is the extent and distribution of the world’s oceans?
What techniques are used to map the ocean floor?

3. What is oceanography? Interdisciplinary science
Draws on methods/knowledge of geology, chemistry, physics, biology

4. Ocean Geography Earth’s surface area: ~510 million km2
Oceans + marginal seas (Mediterranean, Caribbean, etc.): ~360 million km2 (71%)
Northern hemisphere: 61% water, 39% land
Southern hemisphere: 81% water, 19% land

5. Distribution of Land & Water

6. Uneven Land & Water Distribution

7. Four Ocean Basins + Pacific Atlantic
> half of total ocean surface area – all continents could “fit” in it 
Deepest (3940 meters)
Atlantic
Half the size of the Pacific
Average depth is 3339 meters
Land that drains into the Atlantic covers four times that of either the Pacific or Indian oceans

8. Four Ocean Basins + Indian Arctic
About the same average depth as Atlantic but slightly smaller
Mostly in Southern Hemisphere
Arctic
Surface area is ~ 7% of Pacific Ocean
25% as deep

9. Four Ocean Basins + Southern Ocean Meeting of currents near Antarctica
Portions of Pacific, Atlantic & Indian south of 50 latitude

10. Four Ocean Basins +

11. Four Ocean Basins +

12. Comparing the Oceans to the Continents
Continents – 840 meters above S.L. (average)
Oceans – 3729 meters deep

13. The Global Ocean
An Emerging Picture of the Ocean Floor

14. Mapping the Seafloor HMS Challenger (1872-1876)
1st comprehensive study of global ocean
Measured water depth using weighted lines

15. Mapping the Seafloor

16. Mapping the Seafloor

17. Modern Bathymetric Techniques
Bathymetry – measurement of ocean depths and the charting of the topography of the ocean floor
SONAR – sound navigation and ranging

18. Modern Bathymetric Techniques
Echo sounders
Early 20th century
Transmit sound wave (ping) that echoes when it hits an object
Travel time is measured
Depth =

19. Mapping the Seafloor
Scientists "See" Ocean Floor via Sonar Side Scan SONAR

20. Viewing the Ocean Floor From Space
Radar altimeter measures ocean surface height variations induced by ocean floor topography.
Better resolution but much higher cost if an echo sounder is used.
When interesting features are discovered in satellite gravity measurements, these can be surveyed in fine detail by ships.

23. Seismic Reflection Profiles
Strong low-frequency sounds are produced by depth charges.
Used to estimate the properties of the Earth's subsurface from reflected seismic waves.

24. Provinces of the Ocean Floor
Continental margins
Deep-ocean basins
Oceanic (mid-ocean) ridge

25. Provinces of the Ocean Floor