I took my first college courses at the age of six, because Mom got a job and Dad took me to work with him as he taught geology and geography during summer school. I was fascinated by the lesson on how rivers matured. As the coursing water bounces off the banks from side to side, it creates meanders, which widen until they are completely cut off from the main flow, creating oxbow lakes. There’s a pretty good explanation of the process here.
Fifty years later, we get to see the process happening on earth, thanks to satellite imagery. Google Earth Engine combined Landsat images of the Ucayali River in Peru over thirty years time to illustrate the advancing meanders, which culminate in the creation of an oxbow lake. Read more about this particular progression at Hindered Settling. (via Boing Boing)