Mariana Arc of Fire National Wildlife Refuge

The Mariana Arc of Fire National Wildlife Refuge isan arc of 18 undersea mud volcanoes and thermal vents. This arc of undersea mud volcanoes and thermal vents is part of a very geologically complex region including a subduction zone, back-arc basins, and active and potentially active island and submarine volcanoes. The area represents the only place on Earth with huge (largest = 31-mile diameter and >1-mile high) active mud volcanoes that release hydrogen. The Champagne vent, located at the Eifuku submarine volcano, produces almost pure liquid carbon dioxide, a phenomenon that has only been observed at one other site in the world. The molten Sulfur Cauldron (convecting pool of liquid sulfur) found at the Daikoku submarine volcano is unique; the only other known location of molten sulfur is on Io, a moon of Jupiter. 

The refuge supports unusual life forms in some of the most extreme conditions imaginable. Here species survive amid hydrothermal vents that produce highly acidic and boiling water. The volcanic arc is known to host at least twenty vent fields that support a broad range of organisms, including gastropods, mussels, tubeworms, galatheid crabs, and shrimps. Unlike other reefs across the Pacific, the northernmost Mariana reefs provide unique volcanic habitats that support marine biological communities requiring basalt. 

The vents release hydrogen sulfide and other minerals, which are consumed by the barophilic bacteria, which are then consumed by other microorganisms, which are in turn, consumed by the fish, and so on. The temperature around the vents can reach up to 300° Celsius (572° Fahrenheit). Creatures from the deep show an incredible resistance to temperature extremes by having different proteins which are adapted for life under these conditions; allowing the animals to eat, process food, and reproduce. One animal that thrives near hydrothermal vents is the Bythograea thermydron or "vent crab." 

Maug Crater represents one of only a handful of places on Earth where photosynthesis and chemosynthetic communities of life are known to come together. The caldera is some 1.5 miles wide and 820 feet deep, an unusual depth for lagoons. The lava dome in the center of the crater rises to within 65 feet of the surface. Hydrothermal vents at about 475 feet in depth along the northeast side of the dome spew acidic water at scalding temperatures near the coral reef that quickly ascends to the sea surface. Thus, coral reefs and microbial mats are spared much of the impact of these plumes and are growing nearby, complete with thriving tropical fish.