Hydrothermal vents, often called black smokers, are formed on the ocean floor near geologically active zones. Because deep sea trenches are a feature of active geology, they often contain black smokers. Hydrothermal vents are formed when superheated water in the Earth's crust, warmed by the natural heat of the planet, finds an outlet and shoots up into the ocean. Specialized bacteria uniquely adapted to hydrothermal vents can then convert hydrogen sulfide into food; the bacteria are then consumed by other creatures, including tube worms, giant clams and blind shrimp.
Methane, along with a number of other gases, can, under certain conditions, seep up from beneath the ocean floor. Bacteria, symbiotically woven into other organisms such as mussels, can then convert the gas into organic energy. This organic energy is used by a number of species, including bivalves and tube worms, many of which are unique to the cold seep ecosystem. Cold seeps are a characteristic feature of trenches, because trenches are more geologically active than the rest of the of the ocean floor.
Deep sea trenches are created when tectonic plates interact. Trenches are often formed through subduction, a process that occurs when one plate slides under another. Trenches can also be formed when tectonic plates diverge, spreading apart with a trench in the middle, or transform, moving parallel and opposite to one another. Trenches are often associated with geologic and volcanic activity; a trench runs parallel to the Ring of Fire volcano chain that surrounds the Pacific Ocean, for example.
Deep sea trenches, like the rest of the deep ocean, are immense, biologically active zones with a wide range of highly adapted organisms. The deepest trenches have pressures so extreme that they could crush a human flat within seconds, have little oxygen, are ice cold and pitch black. In the face of these hostile environmental conditions, life has found a way to flourish in ocean trenches. Anglerfish, crabs, anemones, and a number of other creatures navigate the dark trenches, looking for prey or falling bits of organic matter.
