Does the site contain seamount(s)?
Does the site contain hydrothermal vent(s)? Cracks in the ocean floor that emit jets of superheated water loaded with minerals and bacteria. The vents range in diameter from less than an inch to more than six feet. They are usually found at least a mile deep along the mid-ocean ridges. Source: http://www.csc.noaa.gov/benthic/resources/links.