Which two coastal landforms are primarily created by erosion?

The correct answer highlights cliffs and wave-cut platforms, which are both primarily formed through processes of erosion. Cliffs are vertical rock faces that develop as waves continuously erode the base of the coastline, often resulting in steep cliffs. The relentless action of the waves against the rock leads to undercutting, creating a prominent cliff face over time.

Wave-cut platforms are the flat, often rocky areas that form at the base of cliffs as a result of wave action. As waves erode the cliff, debris and sediment are removed and transported, leading to the gradual retreat of the cliff line. The platform is exposed at low tide and showcases evidence of the ongoing erosion process, where waves have cut back into the land.

In contrast, the other options consist of landforms primarily created by deposition or other geological processes. For instance, sand dunes and beaches are formed by the accumulation of sediments, estuaries and deltas by river sediments settling as they meet tidal waters, and coral reefs and lagoons are biological structures built by living organisms in the ocean. This distinction emphasizes the erosive nature of cliffs and wave-cut platforms, as opposed to the accumulative or biological processes that shape the other landforms.