with oceanic spreading centers. The spreading half-rate is approximated to about 12 mm/yr, classifying it as a slow-spreading ridge. Seismic events of Richter magnitude 4 and 4.5 have been detected at the massif. The dominant minerals found at Lost City are ultramafic, composed primarily of olivine and pyroxene with very little silica content. Peridotite (primarily spinel harzburgite) minerals undergo serpentinization and form magnetite and serpentine minerals. Because little to no carbon dioxide or metals are released in the venting fluids, Lost City bears the appearance of a non-smoker, with few particulates to give a smoky appearance. Once pore waters have permeated the surface and return to the surface, aragonite, brucite, and calcite chimneys are formed as calcium carbonates precipitate out of solution. Younger chimneys are primarily brucite and aragonite, being white and flaky in appearance. As vents mature, porosity decreases as precipitates clog fluid pathways. Mineral compositions change with aragonite succeeded by calcite and brucite being removed through dissolution, and the chimneys darken to a grey or brown color. On the side of the Atlantis Transform Fault, the Atlantis Massif wall terminates approximately below sea level, where rock types deform to various mylonitic rocks with deformation fabric minerals of talc, tremolite, and ribbon serpentine. Serpentinization Lost City is an exemplary location for the study of abiotic methanogenesis and hydrogenesis, as serpentinization reactions produce methane and hydrogen. Supplementing Fischer-Tropsch reactions; The reactions are exothermic and warm the surrounding waters via reaction heating, though fluid temperatures are still relatively low (40°–90 °C) when compared to other hydrothermal systems. Furthermore, local pH is increased to values of over 9, which enables calcium carbonate precipitation. Since serpentinization is particularly extensive, carbon dioxide concentrations are also very low. Low temperature, carbon dioxide concentrations, as well as the low hydrogen sulfide and metal content of the plume make the vents more difficult to identify from CTD measurements or optical backscatter methods. Biology Lost City and other hydrothermal vent systems support vastly different lifeforms due to Lost City's unique chemistry. A variety of microorganisms live in, on, and around the vents. Methanosarcinales-like archaea form thick biofilms inside the vents where they subsist on hydrogen and methane; bacteria related to the Bacillota also live inside the vents. External to the vents, archaea, including the newly described ANME-1, and bacteria, including Pseudomonadota, oxidise methane and sulfur as their primary sources of energy. Lost City also supports a variety of