| A | B |
|---|
| CORING | Using tubes to take samples of ocean sediments. |
| SONAR | The use of sound waves to find depth and map the ocean floor. |
| HMS CHALLENGER | A British research ship that studied the oceans in the 1870's. |
| ALVIN | A submarine (submersible) used to study the ocean floor directly. Discovered geyser-like vents. |
| CONTINENTAL SHELF | Smooth, gently sloping surface of continental margin, closest to shore. |
| CONTINENTAL SLOPE | Steeper drop-off of continental margin, at the edge of the continental shelf. |
| CONTINENTAL RISE | The part of the continental margin that extends from the slope to the deep ocean floor. |
| SUBMARINE CANYON | Underwater canyons cut in the continental slope by underwater currents or ice-age rivers. |
| ABYSSAL PLAIN | Extremely flat regions of the deep ocean floor, covered with sediments. |
| RIDGES (Mid-ocean ridges) | Volcanic mountain ranges that run for great distances in the middle of oceans. |
| SEAMOUNT | A single volcanic mountain that rises more than 1000 meters above the ocean floor. |
| GUYOT | A seamount that is no longer growing and has been flattened by wave action so its top is below the ocean surface. |
| REEFS | Structures made by coral that form in shallow water on continental shelves or along the shores of islands. |
| ATOLL | A ring of coral left behind after a volcanic island has sunk beneath the ocean surface; can be an island itself. |
| TRENCH | A deep valley on the ocean floor that forms where one crustal plate moves underneath another; the deepest part of the ocean. |
| ISLAND | The top of a seamount that sticks out and is surrounded by water. |
