Exploring the Deep Ocean

Alvin can dive to ocean depths of 14,764 feet-nearly three miles down. Alvin can rest on the ocean bottom or hover at middle depths for up to ten hours, taking photographs and performing underwater experiments. Alvin is amazing. Many of the 150 to 200 dives Alvin makes annually result in underwater discoveries of unusual sights never before seen.
Alvin is not a man. Alvin is a deep-sea submersible craft capable of carrying up to three occupants. It is owned and operated by the Woods Hole Oceanographic Institution on the east coast of the United States. Alvin was built in 1964, but it has been upgraded and reconstructed many times since then. Alvin's titanium hull, or outside shell, is built to withstand the immense pressure of the deep ocean. Alvin weighs 37,400 pounds and 23 feet 4 inches long. It has a 6-mile range and a top cruising speed of 2 knots. Five hydraulic thrusters propel the craft, and lead-acid batteries power the electrical system.
Inside is an infinite variety of the latest electronic equipment, including a gyrocompass, a magnometer, and a computer. Alvin explores the ocean depths.
Alvin allows researchers to conduct underwater biological, chemical, and geological studies.Special lamps shine light into the black water so observers can see the wonders of the underwater environment. Cameras are mounted on the outside to take underwater photographs, and two external "arms" enable researchers to collect underwater samples.
One day in 1977, Alvin contributed to an amazing discovery. On that day, Alvin was transporting scientists on a routine study. The craft was one and a half miles below the surface of the sea near the coast of the Galapagos Islands. As they looked through the three inch portholes, the scientists were temporarily stunned to see a strange underwater landscape littered with what looked like chimneys. The chimneys were discharging clouds of black smoke into the surrounding water. Clustered around the chimneys were odd creatures that lived totally cut off from the world of sunlight. The scientists were looking at hydrothermal vents and the strange sea creatures that exist near them-an entire system of life based not on sunlight, but on energy from the earth itself.
An unusual kind of animal life lives around these vents. Among the chemicals pouring out of the vents is hydrogen sulfide, a gas that is poisonous to most land-based life. However, bacteria in the seawater near the vents feed on this gas and other dissolved chemicals and minerals pouring from the vents. Then tiny animals feed on the bacteria,and these tiny animals in turn become food for still larger animals. Giant red and white tube worms eight feet tall cluster near the vents and dominate the scene. Tiny shrimps and white crabs feed on the worms while giant clams rest in the sand. In an environment that seems incompatible with life, these creatures are thriving.
Since the first vent was discovered in 1977, hundreds of other vents have been located in oceans around the world. Some of the sites are inaccessible, so scientists have not been able to study them all. However, scientists are planning to trace the development of vents by revisiting some they studied earlier. They want to find out how long vents remain active and if the odd creatures change over time.