Passage:
The Black Sea possesses a unique hydrological structure that makes it one of the world's most exceptional underwater archaeological sites. Unlike most seas, the Black Sea receives massive amounts of fresh water from major European rivers, which floats above the denser, saltier water entering from the Mediterranean Sea. Because these two water layers do not readily mix, atmospheric oxygen is unable to penetrate below a depth of approximately 150 meters. This creates a vast anoxic zone—an environment entirely depleted of dissolved oxygen—that extends down to the seafloor.
Because wood-boring organisms such as Teredo navalis (commonly known as shipworms) require oxygen to survive, they are completely absent from these deep anoxic waters. Consequently, wooden shipwrecks that sank centuries ago remain nearly perfectly preserved on the Black Sea floor, retaining delicate carvings, tool marks, and structural integrity that would have been destroyed in oxygenated marine environments within decades.
Based on the passage, ancient wooden shipwrecks remain remarkably preserved at the bottom of the Black Sea because:
- wood-boring organisms cannot survive in the oxygen-depleted deep waters.Cevap
- Bthe high density of incoming Mediterranean salt water prevents physical erosion of the timber.
- Cthe absence of wood-boring organisms causes atmospheric oxygen to stay near the surface.
- Dfreshwater rivers introduce chemical compounds that shield the wood from decay.