A delta is formed at the mouth of a river. It is often a triangular shape. Sediments -- silt, sand and small rocks -- flow downstream. These materials are deposited in a fan shape where a river meets a lake or the ocean. Many famous delta landforms are found worldwide. Major river systems create the largest deltas. These landforms create fertile areas conducive to fishing, farming and human settlements.
The Nile River delta drains into the Mediterranean Sea and is famous because it is the river where the delta landform was first named by Herodotus, a Greek historian. He identified this landform and coined the term "delta" because the triangular shape of a river delta is similar to the Greek letter, "delta." The fertile lands of the Nile River delta provide a home to many farmers who are able to produce crops two or three times per year. Civilization has thrived on this delta since 4000 BC.
The Mississipi Delta
The Mississippi delta is known as the most famous bird's foot delta. Tides and ocean waves do not have a huge affect on this kind of delta, so many channels form that extend into the sea. The Mississippi delta formed about 5,000 years ago and is active today. The sediments from the Mississippi river have caused the gulf land of Louisiana to advance forward 15 to 50 miles since its existence.This delta consists of a half a million acres of wetlands that are at risk because of human development.
The Yellow River Delta
The Yellow River or Huang River of China carries the heaviest sediment load, making its delta one of the richest in the world. This river carries millions of tons of silt each year. The Yellow River delta has wandered up and down the coastline of China for the past 2,000 years, but times have changed. This delta is in flux because of agricultural and industrial uses of the Yellow River's water. Efforts have been made to direct the flow of the river also. Low flow of water threatens aquaculture and wetlands. Oddly the river floods more also because sediments are settling in it, making it more shallow.
Ganges and the Brahmaputra Delta
Ganges and the Brahmaputra delta is the largest delta landform in the world and is almost 5,000 square miles in size. It began almost 125 million years ago. The delta is formed by three rivers, Ganges, Brahmaputra and Meghna, and is located above the Bay of Bengals. It consists of vast mangrove wetlands known as the Sundarbans that are the legendary home of the royal Bengal tiger. Because of human development, the water in this area is becoming more salty, threatening these wetlands.