1. The Seafloor and its Structures

2. The seafloor is divided into two main regions:
Continental margin – submerged edges of the continents
Deep-sea floor

3. Continental Margin Structures
Continental shelf – gently sloping underwater extension of the continent
Continental break – where the margin abruptly gets steeper
Continental slope – steeply sloping edge of the continental margin
Continental rise – formed by deposited layers of sediment decreasing the steepness of the slope at the base
Submarine canyon – deep canyons formed by erosion and landslides, especially at river mouths

4. Two types of continental margins:
Active Margin
Little or no continental shelf
Steep continental slope
Trench at the base
Passive Margin
Wide continental shelf
Gentle continental slope
Continental rise at base

5. Deep-sea Floor Structures:
Abyssal plain – flat expanse of seafloor
Seamount – underwater volcanic mountain of at least 1000 meters in height
Guyot – flat-topped seamount
Island arc – island chains (usually volcanic in nature)
Mid-ocean ridge – underwater volcanic mountain chain formed by rising magma along a spreading zone

6. Rift valley – v-shaped along the center of the mid-ocean ridge, hydrothermal vents are common
Black smoker – mineral deposits forming a chimney-like structure around hydrothermal vents
Trench – deep depressions in the seafloor, they are the deepest parts of the world ocean (Marianas trench = 36,163 ft)