Deltas

◆ A delta is an area of land, usually triangular shaped, built up at the mouth of a river by the mud and sand it carries there. Its shape accounts for its name, since delta, the fourth letter of the Greek alphabet, is shaped like a triangle (Δ). The Nile delta covers an area of about 10,000 square miles. The Mississippi River delta includes about 15,000 square miles of area, and the river’s slow current builds onto the delta and extends it into the Gulf of Mexico at the rate of about one mile every sixteen years.