EarthRef.org Digital Archive (ERDA) -- Seamounts Enhance the Global Influence of Ridge-flank Hydrothermal Circulation

Description
Seamounts are recognized to influence global hydrothermal fluxes in at least three ways. First, volcanically active seamounts, generally located close to active spreading centers and/or associated with hotspot magmatism, are often hydrothermally active. These systems may vent both high-temperature and low-temperature hydrothermal fluids, although these fluxes are likely to be small compared to those at spreading centers (simply because spreading centers are spatially more common). Second, volcanically inactive seamounts provide access points for entry and exit of ridge-flank hydrothermal fluids, those extracting lithospheric heat on a regional basis across much of the seafloor. Fluid fluxes associated with these systems are much larger than those at spreading centers (probably by a factor of 100-1000), and the heat output of ridge-flank systems is also larger than that of systems at spreading centers, but the influence of ridge-flank circulation on global geochemical fluxes varies species by species and remains less certain. Third, volcanically inactive seamounts may host isolated hydrothermal circulation systems associated with local basement relief. In his keynote presentation for the First SBN Workshop, Andrew Fisher shows that a recent analysis of the dynamics of these systems suggests that they may result in globally-significant fluid fluxes (smaller than conventional ridge-flank fluxes but greater than those at spreading centers or volcanically-active seamounts). The primary thermal influence of these isolated, seamount circulation systems is likely to be local, but they may have biased measurements of seafloor heat flow during earlier studies (particularly in cases where the presence of seamounts was unknown), and their influence on geochemical fluxes remains uncertain. The influence of all of these systems on subseafloor microbiology also remains largely unknown and a focus of much ongoing research.