Describe and explain the formation of an oxbow lake. (6 marks)

An oxbow lake is formed when a meandering river or stream erodes the outer banks of a bend, while the inner banks are deposited with sediment. Over time, this erosion and deposition cause the bend to become more pronounced, until the neck of the meander narrows and eventually breaks through during a flood. The river then takes a new, straighter course, leaving behind a crescent-shaped oxbow lake.

The formation of an oxbow lake can be explained by the process of erosion and deposition that occurs in meandering rivers. As water flows downstream, it follows the path of least resistance, which tends to be along the outer banks of a bend. This causes the outer banks to be eroded, while the inner banks are deposited with sediment. Over time, the bend becomes more pronounced, with the river channel becoming narrower and deeper on the outer banks, and shallower and wider on the inner banks.

During a flood, the river may overflow its banks, causing water to flow across the narrow neck of the meander. The force of the water can erode the neck, causing it to break through and creating a new, straighter channel. The river then continues to flow along this new channel, leaving behind a crescent-shaped oxbow lake.

In conclusion, the formation of an oxbow lake is a result of the erosion and deposition process that occurs in meandering rivers, which causes the bends to become more pronounced over time, eventually leading to the formation of a crescent-shaped lake when the river breaks through the neck of a meander during a flood.