A horseshoe-shaped lake once part of, and now lying alongside, a meandering river with a narrow ‘neck’ between meander loops. When the river breaks through this narrow stretch of land, the old meander becomes a temporary lake; ox-bow lakes quickly fill up and become hollows in the landscape. Rasmussen and Ossa (2011) Phys. Geog. 32, 6, 497 report that ox-bow lakes are indicators of past channel conditions and can be utilized ‘as measuring sticks for geomorphic change’.