| A | B |
|---|
| Continental shelf | The gradually slanting edge of a continent that extends beneath the ocean; relatively flat |
| Continental slope | The section of the ocean floor that dips steeply down from the continental shelf |
| Abyssal plain | A flat seafloor area from 4,000 meters to 6,000 meters below the ocean surface, formed by the deposition of sediments |
| Mid-ocean ridge | An area where new ocean floor is formed when lava erupts through cracks in Earth’s crust on the seafloor |
| Trench | A long, narrow, steep-sided depression in the seafloor formed where one crustal plate sinks beneath another |
| Photosynthesis | A food-making process using light energy from the sun, carbon dioxide, and water that is used by plants and algae |
| Chemosynthesis | A food-making process using sulfur or nitrogen compounds that is used by bacteria living near hydrothermal vents on the seafloor |
| Plankton | Marine organisms that drift in ocean currents |
| Nekton | Marine organisms that actively swim in the ocean |
| Benthos | Marine plants and animals that live on or in the ocean floor |
| Estuary | An area where a river meets the ocean that contains a mixture of freshwater and ocean water and provides an important habitat to many marine organisms |
| Reef | A rigid, wave-resistant, coastal habitat built by corals from skeletal materials and calcium |
| Pollution | The introduction of wastes to an environment, such as sewage and chemicals, that can damage organisms |
| Algal bloom | A sudden and large increase in the population of phytoplankton caused by the runoff of excess nutrients (fertilizers, sewage, etc) from land |
