How can tectonic uplift and subsidence change the shape of a coastline?

Tectonic activity significantly shapes coastlines by altering the relative elevation of the Earth's crust, which dictates how erosional and depositional processes interact with the land.1

• Tectonic Uplift: When coastal regions are uplifted by tectonic forces, the land is raised relative to the sea. If this uplifted terrain consists of massive sedimentary rock, it often becomes subject to intense wave erosion. This combination typically results in the formation of steep, nearly vertical sea cliffs that alternate with irregularly shaped bays and narrow inlets.1
• Crustal Subsidence: In areas experiencing subsidence, or the sinking of the Earth's crust, the land surface lowers relative to the sea level. These environments are generally characterized by the accumulation of sediment. Consequently, such coasts often feature wide, sandy beaches, smooth plains of unconsolidated sediment, tidal flats, and sandbars that parallel the shoreline.1

Ultimately, the specific configuration of a coast is the result of the intensity and interaction of these tectonic movements with local geological structures and ongoing erosional or depositional processes.1