Editing Hydrothermal circulation (section)

==Seafloor hydrothermal circulation==
Hydrothermal circulation in the [[ocean|oceans]] is the passage of the water through [[mid-oceanic ridge]] systems.

The term includes both the circulation of the well-known, high-temperature vent waters near the ridge crests, and the much-lower-temperature, [[diffusion|diffuse]] flow of water through sediments and buried [[basalt]]s further from the ridge crests.<ref>{{Citation|last1=Wright|first1=John|title=Hydrothermal circulation in oceanic crust|date=1998|url=https://linkinghub.elsevier.com/retrieve/pii/B9780750639835500060|work=The Ocean Basins: Their Structure and Evolution|pages=96–123|publisher=Elsevier|language=en|doi=10.1016/b978-075063983-5/50006-0|isbn=978-0-7506-3983-5|access-date=2021-02-11|last2=Rothery|first2=David A.|url-access=subscription}}</ref>  The former circulation type is sometimes termed "active", and the latter "passive".  In both cases, the principle is the same: Cold, dense seawater sinks into the basalt of the seafloor and is heated at depth whereupon it rises back to the rock-ocean water interface due to its lesser density.  The heat source for the active vents is the newly formed basalt, and, for the highest temperature vents, the underlying [[magma]] chamber.  The heat source for the passive vents is the still-cooling older basalts.  Heat flow studies of the seafloor suggest that basalts within the oceanic crust take millions of years to completely cool as they continue to support passive hydrothermal circulation systems.

[[Hydrothermal vent]]s are locations on the seafloor where hydrothermal fluids mix into the overlying ocean.<ref name="German-2014">{{Citation|last1=German|first1=C.R.|title=Hydrothermal Processes|date=2014|url=https://linkinghub.elsevier.com/retrieve/pii/B9780080959757006070|work=Treatise on Geochemistry|pages=191–233|publisher=Elsevier|language=en|doi=10.1016/b978-0-08-095975-7.00607-0|isbn=978-0-08-098300-4|access-date=2021-02-11|last2=Seyfried|first2=W.E.|url-access=subscription}}</ref> Perhaps the best-known vent forms are the naturally occurring [[chimney]]s referred to as [[black smoker]]s.<ref name="German-2014" />