Cold Seep

A cold seep, sometimes called a cold vent, is a place on the ocean floor where fluid rich in hydrogen sulfide, methane and other hydrocarbons seeps out, often forming a pool of dense brine. The name is relative rather than literal: seep fluid is often slightly warmer than the surrounding seawater, but it counts as cold compared to the scalding water of a hydrothermal vent, which can exceed sixty degrees Celsius. Cold seeps form their own biome, supporting communities of species found nowhere else, most of which depend on bacteria that draw energy from the seeping chemicals rather than from sunlight. Over time, reactions between methane and seawater, often driven by bacterial activity, build distinctive carbonate rock formations and reefs around a seep, including deposits of the mineral ikaite.