About 10,000 years ago, as glaciers melted, sea levels gradually rose, causing significant climate and landscape changes. Approximately 7500 years ago, these processes reached the large freshwater Black Lake, one of the deepest reservoirs of the Neolithic era.
First, through the Strait of Gibraltar, the rising waters of the Atlantic filled the then almost dry Mediterranean Sea and then moved to the Marmara Lake, making it saline. Then, through the Bosphorus, the seawater entered the Black Lake. The powerful flow of salt water, accompanied by earthquakes and heavy rains, rapidly raised the lake level by tens of centimeters every day until it was level with the Mediterranean Sea.
Sea water changed the lake’s ecosystem: freshwater flora and fauna died, and the remains of organisms began to decompose on the bottom without oxygen, creating the first accumulations of hydrogen sulfide that still persist at depths of over 150-200 meters. Thus, the Black Lake became a sea, and below a certain level, due to the high concentration of hydrogen sulfide, only bacteria can survive. This phenomenon made the Black Sea known as the “Sea of Dead Depths”.
Thus, the rapid influx of salt water turned the freshwater Black Lake into the Black Sea, forming a unique ecosystem that remains unchanged to this day.