| A | B |
|---|
| continental margin | underwater edge of the continent |
| continental slope | gentle downward slope |
| continental slope | steep plunge 4-5 km to the ocean floor |
| continental rise | between continental slope and ocean floor |
| turbidity currents | an underwater avalanche |
| submarine canyon | deep valleys cutting through the coneinental shelf and slope |
| boundary between continent and crust of the ocean floor | continental slope |
| seamounts | steep sides and a narrow top |
| guyout | flat topped underwater mountains |
| abyssal plains | large, flat areas |
| trenches | long, narrow cracks in the ocean floor |
| deepest trench known to man | Marianna's Trench |
| midocean ridges | underwater mountains |
| reefs | limestone structures containing the shells of animals |
| fringing reef | coral reef that touches the shore of volcanic mountains |
| barrier reef | separated from the shore by a lagoon |
| atoll | surrounds an island that has sunk |
