For many years, people thought the ocean floor was smooth and covered with silt or mud.
Now, radar and sonar measurements, plus many explorations to the ocean floor, have revealed an amazing variety of structures.
There are mountains (even higher than Mount Everest, the highest on Earth’s surface), trenches, canyons, caves, rock formations, and virtually every other kind of topography, or natural structure, we see on land.
Five main components form the structure of the ocean floor. A continental shelf stretches out from land. This shelf is an extension of the continental plate, or land mass. It gradually declines, forming the continental slope, until it reaches the continental rise, the part of the ocean floor inclining to meet the slope.
The floor then extends in an abyssal plain to the raised ocean ridge. Basically, one ocean ridge runs through the middle of the Atlantic, Arctic, Pacific, and Indian oceans. On the other side of the ridge is another abyssal plain reaching to another continental rise, another continental slope, and another continental shelf.
A continental shelf, slope, and rise are together known as a continental margin. The abyssal plains and ocean ridge make up the ocean basin.