| A | B |
|---|
| continental shelf | the gently sloping part of a continent that is under water and rings each continent |
| continental slope | the edge of a continent that drops steeply down to the ocean floor |
| abyssal plain | the vast floor of the deep ocean |
| mid-ocean ridge | place where plates of the Earth's crust along the ocean floor are being split up to form new ocean floor and a mountain range |
| trench | place where two plates of the Earth's crust hit each other, forming a deep part of the ocean |
| seamount | a steep-sided volcanic mountain under the ocean |
| atoll | a ring of islands around a shallow central lagoon |
| intertidal zone | area between the high-tide mark and the low-tide mark |
| coral reef | structure built by living creatures |
| estuary | a place where a freshwater environment and saltwater environment meet |
