What is typically found at the mouth of a river?

At the mouth of a river, it is typically where the river flows into a larger body of water, such as an ocean, sea, or lake. This transition often leads to the formation of a delta, which is a landform created by the deposition of sediment carried by the river as the flow velocity decreases upon meeting standing water. The sediment accumulates over time, leading to the distinctive landforms and ecosystems often seen at deltas.

Other possibilities, such as canyons or waterfalls, are usually found upstream or in the river's middle course and are not characteristic of the river's mouth. The source of the river is located at the opposite end of the river system, where the river begins, making options that refer to sources irrelevant in this context. Understanding the geographical formations and processes at different stages of a river's journey is crucial for recognizing how river systems interact with their environments.