When were coastal plains formed?

Coastal plains were formed over millions of years through processes such as sediment deposition, erosion, and tectonic activity. They typically develop at the edges of continents where rivers deposit sediment into ocean waters, especially during periods of rising sea levels. This process can be traced back to different geological periods, with some coastal plains dating back to the Mesozoic and Cenozoic eras. Their formation is an ongoing process influenced by both natural forces and human activities.