Final answer:
Water erosion leads to the formation of deltas, where river-carried sediments settle at a body of water's mouth, creating low-elevation sand and mud flats.
Step-by-step explanation:
Water erosion.
Erosion is the process that shapes the earth's surface through the wearing away and transportation of materials. When it comes to deltas, they form as a result of water erosion. This occurs when a river carries sediment downstream and reaches a larger body of water, such as an ocean or a lake. Here the water flow slows down significantly, and the transported sediments begin to settle at the mouth of the river. Over time, these sediments accumulate to form deltas, which are typified by their low-elevation sand and mud flats. Notably, deltas are more likely to form in conditions where there is a high silt content in the river water and minimized ocean currents or wave action that could disperse the sediments.
Rivers with high silt content discharging into areas with lesser wave action or ocean currents are particularly efficient at creating deltas, while rivers with less silt or stronger currents and waves tend to create different features such as estuaries.