How can coastal erosion lead to a landslide spread?

Coastal erosion contributes to the development of a landslide spread by oversteepening the base of a slope. When natural erosion removes material from the base of a coastline, it increases the shear stress within the slope, potentially causing it to exceed the material's shear strength.12

A spread is a specific type of landslide characterized by the complex lateral movement of relatively coherent earth materials resting on a weaker substrate. As the coastline erodes, it can trigger a retrogressive extension—a process where the instability moves progressively further inland from the point of origin. This allows the slow, downslope movement of coherent blocks to extend over long distances as they subside into the weaker, underlying substrate. This process is often exacerbated if the substrate is susceptible to liquefaction due to water saturation.1