How was the Danube delta formed along the Black Sea coast?

The Danube delta is a relatively young geological formation. Approximately 6,500 years ago, the site where the delta now exists was a shallow cove along the Black Sea coast. Over time, this area was gradually filled by river-borne silt deposited by the Danube River.

The formation of the delta is a result of the river delivering sediment to the shore at a rate that exceeds the capacity of marine processes to remove it. As the river reaches its mouth near Tulcea, it splits into three primary channels—the Chilia, Sulina, and Sfântu Gheorghe—which continue to distribute sediment across the region. This process of accumulation remains active today, causing the delta to grow seaward at an annual rate of 80 to 100 feet (24 to 30 metres).123