Ocean Floors

Few locations are as remote as the deep oceans. Although we have walked on the moon and seen the surface of Mars, we have explored less than 1% of the Earth's sea floor with our own eyes.

Underwater exploration is difficult. The ocean is vast and the deep seas are permanently dark and bone-chillingly cold. The pressure at great depths can reach more than 16,000 pounds (the weight of an adult elephant) per square inch. Remote sensing from the air and from space provide a sweeping view of the ocean's surface but detailed observation of the ocean's depths relies on submersible vehicles. Remotely Operated Vehicles (ROVs) and Automatic Underwater Vehicles (AUVs) excel at high speed, long term and large area explorations. But there is no substitute for human eyes. Submersibles carrying people often make the final, significant observations.

A tiny ship in a great sea would have little chance of making major discoveries without years of preliminary work. Scientists first use side-scan sonar Like GLORIA (see inset at right) from surface ships to map areas of potential interest. They plant transponders along the ocean floor to allow pinpoint navigation. Using the signals from the transponders a camera is towed along the bottom taking photographs automatically. Finally, scientists study the photos to choose those few places worthy of first hand observations. Even with all this preparation, scientists don't always find what they are looking for in the eternal darkness of the deep sea. But in the last 20 years, startling new communities of animals have been found around hot springs on the ocean floor.

People have always wanted to explore the sea, to look for sunken treasure, to salvage wrecks, to bring up marine products like pearls and sponges, or to simply examine the beautiful underwater world.

Oceanography is a branch of science that studies all aspects of the ocean's physical features and inhabitants. It is the study of anything about the oceans: the description of land surrounding them, the plants and animals that live in them, how the oceans affect humans, and how humans affect the oceans. Oceanography is not a separate science but encompasses many sciences, such as biology, chemistry, geology, physics and geography.

The scientists and explorers of earlier times could only guess what lay below the waves. Now, underwater instruments and machines can tell us. Some devices tell us about the water itself. Research ships lower bottles that fill with water at different levels in the sea; thermometers fixed to the bottles measure the temperature at these levels. Ships tow bathythermographs to record how underwater temperature and pressure change across an ocean. Complicated devices called bathysondes measure underwater saltiness, temperature pressure and the speed of underwater sounds. In order to learn how underwater currents flow, researchers use special buoys and floats that send back signals to the surface.