Exploring the Oceans    Underwater Explorations

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Geologic LOng Range Inclined ASDIC

GLORIA: Geologic LOng Range Inclined ASDIC

GLORIA is a digital side-scan sonar system used for over 20 years to survey the ocean floor. This electronic mapping system is towed behind its mother ship at a speed of 10 knots. Pulses of sound span out across the seabed up to 18 miles (30 km) on each side. The echoes that bounce back from features on the seabed are picked up and processed by onboard computers to produce maps of the seafloor. These maps help identify hazards on the seabed, determine routes for laying undersea cables, and assist in exploration for valuable minerals.

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.


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