1. Oceanography The scientific study of the oceans and oceanic phenomena.

2. Bathymetry The measurement of ocean depths and the charting of the shape or topography of the ocean floor.

3. Submersible A small underwater craft used for deep sea research.

4. Sonar An electric depth-sounding mechanism; sonar calculates ocean depth.

5. Continental Margin That portion of the seafloor adjacent to the continents.

6. Continental Shelf The gently sloping submerged portion of the continental margin, extending from the shoreline to the continental slope.

7. Continental Slope The steep gradient that leads to the deep-ocean floor and marks the seaward edge of the continental shelf.

8. Submarine Canyon A seaward extension of a valley that was cut on the continental shelf during a time when the sea level was lower.

9. Turbidity Current A downslope movement of dense, sediment- laden water created when sand and mud on the continental shelf and slope are dislodged and thrown into suspension.

10. Continental Rise The gently sloping surface at the base of the continental slope.

11. Ocean basin floor Area of the deep-ocean floor between the continental margin and the oceanic.

12. Abyssal plains Very level area of the deep-ocean floor, usually lying at the foot of the continental.

13. Seamount An isolated volcanic peak that rises at least 1000 meters above the deep-ocean floor.

14. Mid-ocean Ridge A continued elevated zone on the floor of all the major ocean basins and varying in width from 1000 to 4000 kilometers.

15. Seafloor Spreading The process by which plate tectonics produces new oceanic lithosphere at ocean ridges.