In 1977, deep sea submariners from Woods Hole Oceanographic Institution who were surveying the ocean floor came across a startling discovery: a hydrothermal vent, teeming with life. A hydrothermal vent forms when there are cracks in the Earth's surface underwater through which magma and lava can seep. Although scientists had conjectured that hydrothermal vents existed, this discovery confirmed the hypothesis, and revealed that hydrothermal vents played host to a wide range of extremophilic life forms, which thrived in the harsh environment along the ocean floor. Since 1977, a small group of scientists has continued to study these unusual and fantastic interconnected colonies of unique organisms.
The most common location for a hydrothermal vent is along mid ocean ridges, because this is where tectonic plates are separating and forming new sea floor. Intensely cold, highly pressurized water which is close to the freezing point seeps into small cracks, where it comes into contact with extremely hot molten rock. The temperature of the water is rapidly elevated to 750 degrees Fahrenheit (400 degrees Celsius) or more, and jets back out of the crack to form a plume of highly mineralized material. The water of a hydrothermal vent does not actually boil, because the pressure of the ocean elevates the boiling point, but it does carry dissolved minerals, especially sulfides, creating a highly visible geyser. This plume makes a hydrothermal vent much easier to find, once scientists know what they are looking for.
Many hydrothermal vents create towers of minerals where they come into contact with the intensely cold ocean water, and these piles play host to chemosynthetic bacteria, which rely on the materials in the mineralized plume for energy, rather than sunlight. When scientists were able to prove that chemosynthetic bacteria truly existed, it raised questions about life on Earth and other planets, and suggested that there might be colonies of extremophilic organisms on other places on Earth, or in the solar system in general. That anything lives at all around a hydrothermal vent is amazing: the temperature differences are extreme, and the pressure is immense.
Larger organisms around the hydrothermal vent in turn prey on the smaller ones, creating a unique web of life deep under the ocean. Some of the larger creatures found at hydrothermal vents include bizarre looking tube worms, which lack digestive systems of their own and rely on symbiotic bacteria to provide their nutrition, and giant clams. The environment around a hydrothermal vent is rich with materials, many of which are also valuable to humans, but it is unlikely that hydrothermal vents will ever be exploited for their resources. In addition to being highly delicate environments, they are also extremely hard to access, and may provide valuable services to the environment. For example, chemosynthetic bacteria are used to help clean up chemical spills, converting dangerous materials like hydrogen sulfide to energy.