Largest meromictic basin

With an an area of around 508,000 km² (196,000 miles²) and a maximum depth of 2,245 m (7,365 ft), the Black Sea is the world¹s largest meromictic lake ­ that is, a body of water characterized by layers of water at different densities. These stratified waters do not mix, as there is little movement of the water. The upper layer (10%) of the Black Sea contains oxygen and 17.5 g per litre of salt (0.017 oz per fluid oz); the remaining 90% has almost no oxygen and a salinity of 22.5 g per litre (0.022 oz per fluid oz). Trapped in the lower layer is toxic hydrogen sulphide that, if released by an earthquake, could kill thousands of people.