What may cause a change in a river's base level?

A river's base level is defined as the lowest point to which a river can erode its bed, typically determined by the level of the body of water into which it flows, such as a lake or the ocean. Isostatic adjustment can cause changes in a river's base level due to the movement of the Earth's crust. As glaciers melt or tectonic plates shift, the land can rise or fall. This change in elevation can alter the height of the river's base level, leading to either a relative rise or fall in the water level and, subsequently, influencing the river's erosion and sediment deposition processes.

For instance, if the land rises due to isostatic rebound after ice sheets melt, the base level of a nearby river may decrease, causing the river to erode more deeply into its bed. Conversely, if the land subsides, the base level can rise, leading the river to deposit sediment and potentially flood surrounding areas. This dynamic interaction illustrates why isostatic adjustments are significant in shaping a river's base level over time.