In the late 1950s, the bathyscaphe (deep boat) Trieste was the first manned vehicle to venture to the deepest parts of the ocean, a region of the Marianas Trench named the Challenger Deep. Of course, some scientific research requires actually traveling to the bottom of the ocean to collect samples or directly observe the ocean floor, but this is more expensive and can be dangerous. Researchers send a pulse of sound down to the ocean floor and calculate the depth based on how long it takes the sound to return. SONAR, which stands for Sound Navigation And Ranging, has enabled modern researchers to map the ocean floor much more quickly and easily. In the 19th century, explorers mapped ocean floors by painstakingly dropping a line over the side of a ship to measure ocean depths, one tiny spot at a time.
Today’s submarines usually dive to only about 500 meters to go deeper than this they must be specially designed for greater depth (Figure 14.20).įigure 14.21: Alvin allows for a nine hour dive for up to two people and a pilot. In the ocean, for every 10 meters of depth, the pressure increases by nearly 1 atmosphere! Imagine the pressure at 10,000 meters that would be 1,000 kilograms per square centimeter (14,700 lbs/sq in). It presses down on us with a force of about 1 kilogram per square centimeter (14.7 lbs/ sq in). Even though we don’t think about it, the air in our atmosphere has weight. The pressure on a diver at 40 meters would be 4 kilograms/square centimeter (60 lbs/sq in). Scuba divers can rarely go deeper than 40 meters due to the pressure. Finally, the pressure in the ocean increases tremendously as you go deeper. Such cold temperatures pose significant obstacles to human exploration of the oceans. Secondly, the ocean is very cold colder than 0☌ (32☏) in many places.
Most places in the ocean are completely dark, which makes it impossible for humans to explore without bringing a source of light with them. As you know, light only penetrates the top 200 meters of the ocean the depths of the ocean can be as much as 11,000 meters deep. Three main obstacles have kept us from studying the depths of the ocean: absence of light, very cold temperatures, and high pressure.
Figure 14.19: Dolphins and whales use echolocation, a natural sonar system, to navigate the ocean.
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