The following article is from the book Uncle John’s Bathroom Reader Nature Calls.
Where can you find the world’s tallest mountains, most active volcanoes, and deepest canyons? Hold your nose and jump in, because they’re all on the ocean floor.
According to the United States National Oceanic and Atmospheric Association, about 95 percent of the ocean floor remains unmapped. And since the world’s five oceans cover nearly 140 million square miles, that leaves a whole lot left to explore. Earth’s oceans are…
• The Pacific is, by far, the world’s largest ocean. With an area of more than 60 million square miles, it covers about 28 percent of the earth’s surface, making it nearly equal in size to all of the landmasses on the planet combined.
• The Atlantic is the second largest, covering about 21 percent of the earth’s surface with an area of 41.1 million square miles.
• The Indian Ocean comes in as the third largest ocean, covering roughly 26.5 million square miles.
• The Southern, or Antarctic Ocean was once considered part of the Pacific. Now it’s the fourth largest ocean with its southern boundary on the freezing coast of Antarctica. It covers an area of roughly 7.8 million square miles.
• The Arctic is the world’s smallest ocean and the one that is the farthest north. Most of it lies above the Arctic Circle, covering 5.4 million square miles.
HOW LOW CAN YOU GO?
If you were to step off the land of any continent where it meets the ocean, you’d step onto the “continental margin,” the shallowest part of the ocean floor. It includes these three areas:
• The continental shelf is a section of land that’s connected to the rim of a continent. It slopes downward gradually at an angle of one to three degrees. Some continental shelves are narrow, some are wide, and they can stretch for miles. Continental shelves make only 8 percent of the ocean floor, but they’re the part that fishermen and geologists know best. They have lots of sunlight and fertile soil deposited by rivers, streams, and coastal currents. Seaweed, plankton, and microbes grow there and feed the fish that exist in greater numbers and varieties on the continental shelf than anywhere else in the ocean. There are also often minerals, gas, and oil found in the rocks that form continental shelves.
• The continental slope starts at about 450– 650 feet below sea level. Where the shelves end and the continental slopes begin, the land drops off steeply. Continental slopes fall away so quickly that the ocean becomes thousands of feet deeper within a couple of miles. Here, the water is much colder. It has less oxygen and is home to less marine life.
• The continental rise lies just below the continental slope and forms the end of the continental margin. The continental rises are created from the mud, silt, and sand that are deposited on the continental shelves by streams and rivers. Currents pick up the sediment and send it tumbling down the steep sides of the continental slopes until it lands in the continental rises.
The article above is reprinted with permission from Uncle John’s Bathroom Reader Nature Calls. From hornywinks to Dracula orchids, from alluvium to zymogen, Uncle John is embarking on a back–country safari to track down the wackiest, weirdest, silliest, and most amazing stories about the natural world.
Since 1988, the Bathroom Reader Institute had published a series of popular books containing irresistible bits of trivia and obscure yet fascinating facts. If you like Neatorama, you'll love the Bathroom Reader Institute's books - go ahead and check 'em out!