Volcanic heat at the mid-ocean ridge axis drives hydrothermal circulation and chemical exchange between the ocean crust and seawater. A mid-ocean ridge hydrothermal system, plume, and resulting deposits and precipitates are featured. Some metals represented: Mn = Manganese, Mg = Magnesium, Co = Copper, Zn = Zinc, Fe = Iron. Some gases represented: 3He = Helium from the Earth's mantle, H2 = Hydrogen, CH4 = Methane, H2S = Hydrogen Sulfide, CO2 = Carbon Dioxide. The boiling point of water at sea level is 100 degrees C (Celsius) or 200 degrees F (Farenheit). 350 degrees C = 690 degrees F. Image courtesy of Submarine Ring of Fire 2002, NOAA/OER.