hot hydrothermal vents on the floor of the Pacific and Atlantic Oceans. They are located where the ocean floor is spread- ing as new portions of the Earth’s crust form by a gradual upwelling of material from the Earth’s interior (Figure 1–11). Downward-percolating seawater is heated and driven back upward as a submarine geyser, carrying with it a current of chemicals from the hot rocks below. A typical cocktail might include H 2 S, H 2 , C O, Mn 2+ , Fe 2+ , Ni 2+ , CH 2 , NH 4 + , and phosphorus-containing compounds.