¶ … Features of the Ocean Floor Continental Margins

As one travels away from the continents, water depths increase in a systematic manner.

Closest to the continents are continental shelves with water depth typically less than 1000 m. Continental shelves were formed as rivers carried tons of particles of sand and soil from the land out to sea. This sand and soil then settled as layers of sediments, or layers of particles of rock and animal remains.

Commonly at the distal edge of the continental shelves, there is a marked continental slope where water depths increase quickly. The continental slope separates the continental shelf from the ocean floor.

The continental rises, located at the base of the continental slopes, mark the beginning of the deep ocean basins.

Submarine canyons commonly occur along continental margins and transport sediment from the margins down into the deep ocean basins.

B. Mid Ocean Ridges

Long mountain chains found in the deep ocean basins of all major oceans.

1) The mid ocean ridges commonly occur far from continental margins and on the edges of deep-sea basins.

2) The ridges commonly have long fracture zones associated with them; the fracture zones occur on both sides of the ridges and run perpendicular to them.

C. Deep Ocean Basins

Topographic basins bounded by Mid Ocean Ridges and Continental Slopes.

1) Many plains on the ocean basin are larger and flatter than any found on the Earth's surface. They are called abyssal plains. Abyssal plains are form by sediments deposited by turbidity currents. It sediments continually falling from the seawater above.

D. Deep Sea Trenches

The deepest parts of the ocean are long linear trenches, which commonly occur adjacent to continental margins.

E. Oceanic Rises

Throughout the oceans are located isolated topographic highs...

When these reach the ocean surface they may contain reefs. Other terms that are associated with seamounts are guyots, and atolls.
2) Oceanic Plateaus

There are several regions of the oceans, which are really drowned continents.

Ocean Floor Sediments

A. Biogenous Sediments

Biogenous sediments are particles that are produced directly by marine organism.

Example: Calcareous, siliceous oozes

B. Hydrogenous Sediments

Hydrogenous sediments are form either by direct precipitation from seawater or as a new mineral from chemical reactions between seawater and sediments on the sea floor.

Example: Manganese nodules, phosphorus deposits, salt and gypsum

C. Terrigenous Sediments

Terrigenous sediments are produced by the physical and chemical "weathering" of rocks exposed on continents.

Example: Quartz sand, clays, mud, glacial

Oceanic current systems

Large oceanic current systems have names and description based on their average locations. The water transport and speed of a current is affected by the current's cross-sectional area, by the other currents, by westward intensification and by wind speed.

A. The Pacific Ocean Currents

In the North Pacific Ocean, the northeast trade winds push the water toward the west and northwest; this is the North Equatorial Current. The Westernizes create the North Pacific Current, or North Pacific Drift, moving from west to east.

In the South Pacific Ocean, the southeast trade winds move the water to the left of the wind and westward, forming the South Equatorial Current. The westerly winds push the water to the east; at these southern latitudes the surface current so formed can move almost continuously around the earth. This current is the West Wind Drift.

B. The Atlantic Ocean Currents

The North Atlantic westerly winds move the water eastward as the…