Ocean Floor Physiography The ocean floor can be divided into features called physiographic provinces. These provinces are distinguished from each other by depth, general slope of the surface, and composition of the substance. 1. Continental Margins
· Underwater extension of the continents
· The margin comprises about 1/3 of the Atlantic Ocean floor
· Subdivided into three parts: shelf, slope and rise: Continental shelf:
· shallow, relatively flat, close to land
· abundant in sea life Continental Slope:
· sharp gradient; continues to a depth of 3600m
· example: Hudson Canyon Continental Rise:
· made of sediments from continents, slope and shelf 2. Abyssal Floor:
· Deepest part of ocean basin (other than trenches)
· Avg. depth = 4000m
· Dark, near freezing, great pressure 3. Ocean Ridges:
· · · · Continuous chain of underwater mountains
1000s of km wide
Can protrude above sea level, creating islands (Iceland)
Bisects the Atlantic Ocean – called Mid Atlantic Ridge
· Form at divergent plate boundaries 4. Ocean Trenches
· · · · Deep troughs in abyssal floor
Up to 6000m deep
Convergent plate boundary (subduction zones)
Found in the Pacific ocean