Describe how meanders form, develop, are cut off, and then are abandoned.

Understanding the constant interplay between river erosion and deposition is essential when studying the dynamic nature of river landscapes. Imagine a river as a natural sculptor, constantly carving and shaping its path as water flows towards the sea.

Erosion primarily occurs on the outer edges of river bends where the water speed is greatest. Here, the centrifugal force exerted by the flow of water swings it against the bank, grinding away soil and rock in a process called lateral erosion. This action is most intense on the outer banks of meanders, leading to their outward expansion.

On the flip side, deposition acts as nature's construction phase. The inner banks of a meander experience slower water flow, which causes sediment to settle out of the water column and accumulate. This deposition creates gently sloping areas known as point bars.

The constant push and pull of erosion and deposition not only defines a river's meandering character but also paves the way for intricate habitats to thrive along the river's course. It's a natural balancing act where gain and loss of materials continuously reshape the river's journey.

A meander cut-off is like a shortcut in the winding journey of a river. Over time, rivers do not follow the same path. The forces of erosion gradually eat away at the necks of large bends, and during periods of high flow, such as during floods, rivers may forge new, more direct paths.

In a dramatic reshaping event, the most eroded points of two outer banks within a meander can become so thin that it takes just a small nudge—a heavy rainfall or snowmelt, for instance— for the river to break through. This creates a new channel segment, leaving the old loop largely detached from the main flow of the river.

The inception of this cut-off is a striking example of how rivers constantly alter their courses, seeking the most efficient route downhill, a principle you could visualize as water’s relentless pursuit of the path of least resistance.

Following a meander cut-off, the abandoned river bend embarks on a slow transformation to become an oxbow lake—a serene U-shaped body of water that stands as a monument to the river’s former path.

Initially, the oxbow lake remains filled with water and can be quite deep. However, it's no longer receiving the same influx of fresh water and sediments. Thus, deposition becomes the prevailing force, while erosion takes a back seat. The reduced flow means that sediments carried by the water start settling at the bottom of the lake, gradually filling it in.

Plants also begin to colonize the still waters and edges, contributing organic matter that further accelerates the filling process. Over years or sometimes much quicker, the oxbow lake may become a swamp or a marsh, and eventually, it may dry up completely, becoming an oxbow scar on the landscape. The legacy of the meandering river is a mosaic of water bodies and fertile lands cradling a diversity of life, an ecological testament to the river's past.