Hot vent fluid enters the ocean at high-temperature hydrothermal vents, also known as black smokers. Because of the large temperature difference between the vent fluid and oceanic near-bottom waters, the hydrothermal effluent initially rises as a buoyant plume through the water column. During its rise, the plume engulfs and mixes with background ocean water. This process, called entrainment, gradually reduces the density of the rising plume until it reaches its level of neutral buoyancy, where the plume density equals that of the background water, and it begins to spread along a surface of constant density. (For a much more detailed discussion of buoyant hydrothermal plumes, see Di Iorio et al., 2012, in this issue.)

Thurnherr, A.M., and L.C. St. Laurent. 2012. Turbulence observations in a buoyant hydrothermal plume on the East Pacific Rise. Oceanography 25(1):180–181, https://doi.org/10.5670/oceanog.2012.15.

Di Iorio, D., J.W. Lavelle, P.A. Rona, K. Bemis, G. Xu, L.N. Germanovich, R.P. Lowell, and G. Genc. 2012. Measurements and models of heat flux and plumes from hydrothermal discharges near the deep seafloor. Oceanography 25(1):168–179, https://doi.org/10.5670/oceanog.2012.14.
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