Geology and hydrology are intertwined. When the mountain grows or erodes, it changes the flow and composition of the river. When its glaciers melt the water level increases, when there is no snowpack the river recedes. The river meanwhile cuts into the mountain, metabolises its minerals into biodiverse ecosystems, and populates the mountain seasonally with those organisms. As one changes the other will irreversibly change in response. If one stops its function, the processes shaping the other no longer occur and it becomes something different. Over time we'll see the canyon or the desert where there was once a plateau or stream.
I like using nature as the proof of dialectics because you can point at it. There's a clear and easy to understand sense of historical materialism when can use your immediate surroundings.