Pawtuxet's Oxbow Lake
Animation - from a British school portal
Definition - from Merriam-Webster
A crescent-shaped often ephemeral lake formed in the abandoned channel of a meander by the silting up of its ends after the stream has cut through the land within the meander at a narrow point.
Formation - from Wikipedia, the free encyclopedia
When a river reaches a low-lying plain in its final course to the sea or a lake, it meanders widely. Deposition occurs on the convex bank because of the ‘slack water’, or water at low velocity.