Illustration explaining how a Deep Hypersaline Anoxic Basin (DHAB) forms

DHABs form when salt from long-buried deposits reaches the seafloor and dissolves into the ocean. The resulting extra-salty, ultra-dense water does not mix with normal, less dense, oxygenated seawater above it and gets trapped in seafloor valleys. The interfaace is the zone between the two types of water. (Illustration by Jack Cook, © Woods Hole Oceanographic Institution)