Final answer:
Discordant coasts feature headlands and bays due to differential erosion, where softer rock erodes to create bays and harder rock forms headlands. Over time, marine processes like wave action transport sediment, smoothing out these irregularities. Aggradation and erosion gradually level out the seabed, leading to a more uniform coastline.
Step-by-step explanation:
Headlands and bays are prominent features of discordant coasts, which form where different types of rock erode at different rates. Over time, mechanical action from ocean waves tends to erode softer rock to form bays, while harder rock resists erosion and projects out as headlands. This differential erosion creates the jagged coastline characteristic of discordant coasts. Gradually, marine processes including wave action and sediment transport work to smooth out the irregularities of such a coast through the mechanisms of aggradation and erosion.
The maritime forces move sediment from areas of high energy, such as headlands, where waves constantly pound the rocks, to areas of lower energy, such as bays, where sediment can settle and accumulate. This process is enhanced during periods of lowstand, when sea levels are lower, exposing the continental shelf and facilitating the transport of a greater volume of sediment into marine basins.
Over time, the sediment accumulated in the bays builds up, gradually levelling out the seabed and thereby creating a more uniform coastline, while the headlands are slowly worn down by continuous wave erosion. In this way, discordant coasts naturally evolve towards a smoother outline.