What is an oxbow lake?

An oxbow lake is born from the natural wandering of a river across a flat plain. Over time, a river erodes the outer banks of its bends and deposits sediment on the inner banks, making the loops, or meanders, grow ever more exaggerated. Eventually a big loop becomes so pronounced that the river carves a shortcut across its neck during a flood, abandoning the old curve. Sediment then seals off the ends of that loop, leaving a standalone crescent-shaped body of water called an oxbow lake. These lakes gradually fill with sediment and vegetation over the years, eventually becoming marshes or meadows. They are common along mature, slow-moving rivers.