The objective of the Alvin’s mission was to find hydrothermal springs—undersea geysers that shoot jets of heated water into the ocean.

Their lights revealed a number of shimmering warm-water vents on the seafloor, where the water is normally near freezing. Close to the vents, something even stranger appeared—entire communities of previously unknown living creatures. Two years later, researchers aboard the Alvin discovered superheated vents called smokers on the East Pacific Rise off the coast of Mexico. A number of these vents formed ghostly chimneys, some up to 30 feet [9 m] tall.

Because of its highly unstable and volcanic nature, the globe-encircling mid-ocean ridge system is riddled with lava flows and hydrothermal vents. The vents spew out a toxic, superheated concoction of water and dissolved minerals from inside the earth. Yet, amazingly, this inhospitable realm, which is also under pressures hundreds of times greater than those at sea level, does not repel life but, rather, attracts it—and in abundance!

The stench comes, not from decay, but from hydrogen sulfide—an offensive-smelling and highly poisonous chemical that is abundant in hydrothermal vents. Vent water is also highly acidic and contains many metals, including copper, magnesium, iron, and zinc. But instead of barely coping in this environment—which has been compared to a toxic-waste site—tube worms and other creatures thrive!

Energy From the Belly of the Earth

Ingeniously, the Creator has arranged for the belly of the earth to provide the necessary energy via the hydrothermal vents and that obnoxious-smelling compound hydrogen sulfide. As the “sunlight” of the vent community, hydrogen sulfide provides the energy that the bacteria need to have to go about their food-manufacturing business.

An Eerie Light!

In 1985, scientists were surprised when near the vents they found shrimps that have two eyelike organs with light-sensitive chemicals but no lenses. Of course, the first question that came to mind was, What could these animals possibly see in a world of total darkness? In order to find out, researchers made use of a highly sensitive digital camera, such as is used to photograph faint stars. They aimed the camera at a vent, turned off all their lights, and took a picture.

The result was amazing. The picture revealed “a dramatic, unequivocal glow with a sharply defined edge” where the jet of hot water left the chimney, says scientist Cindy Lee Van Dover. Do the shrimps exploit this eerie light, which is invisible to human eyes? Whatever the case, the discovery that hydrothermal vents glow “opens up a whole new area of research,” adds Van Dover.

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What Are Hydrothermal Vents?

Along the volcanic mid-ocean ridge system, seawater creeps down through cracks in the crust to areas that are extremely hot. The water then becomes superheated, reacts with rock, and absorbs a number of chemicals. It also becomes more buoyant, rises to the seafloor, and forms hydrothermal vents—hydrothermal springs or geysers. These “easily rival their terrestrial analogs in power and spectacle,” says one reference.

Furthermore, the temperature of these seafloor springs can approach 750 degrees Fahrenheit [400°C.], which is hotter than molten lead! But because of the pressure exerted by miles of ocean above, the superheated brew does not turn to steam. Amazingly, less than an inch away from a hot jet, the ambient sea temperature is usually just a few degrees above freezing. Minerals precipitating out of quickly cooling springs settle to the seafloor, where they form mounds and chimneys. The latter may rise to 30 feet [9 m]. One chimney, in fact, was found to be 150 feet [45 m] high and nearly 40 feet [10 m] in diameter, and it was still growing!

Hydrothermal vents can turn on and off sporadically, which makes life around vents a precarious existence. Some creatures, however, may survive by migrating to other vents.

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P. Rona/OAR/National Undersea Research Program