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| Hydrothermal plumes | |||||
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This is a cartoon showing a typical submarine volcano
that you might find along the Kermadec arc. |
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Here we try to detect the plumes that are expelled from the volcanoes, only these are a result of venting hydrothermal fluids (hot water/gas) and not (typically) ash. During magma ascent, water and gases contained in magma exsolve as pressure is released and they also move upwards causing hydrothermal alteration of the host volcanic rock (white) as hydrothermal fluid is quite acidic. These hot (~400°C) 'magmatic' fluids (red arrows) are typically metal-rich and locally mix with heated seawater (blue arrows). Combined, these hydrothermal fluids are expelled from vents on the seafloor into the overlying, cold seawater, where there is a tremendous chemical reaction - metals such as zinc, copper and gold which were quite happy to be in solution at 350°C are most unhappy to be mixed with 2°C seawater and consequently precipitate out as fine-grained mineral floccuants and form what are commonly known as "black smoker" plumes. These plumes rise until they become neutrally buoyant then drift off with the prevailing current. The vents that expel the plumes at these sites commonly take the form of few metre high 'chimney' structures. |
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