General concavity or convexity of sea-cliff profiles is controlled by relative rates of erosion by marine and subaerial processes, as well as by positions of more resistant strata in the cliffs. Profiles supplemented by on-site examination can establish the activity and dominance of erosional processes and indicate changes in regimen. A sharp angle at the sea-cliff base generally indicates active marine erosion, whereas a smooth curve at the base means that subaerial erosion may dominate. Talus shows absence of marine erosion. Studies of profiles can be useful for estimating stability for residences, railroads, and highways at the top, face, and base of sea cliffs. Generally increased erosion and retreat of sea cliffs are in prospect because of projected regionally wetter and stormier climate, rising sea level, and increased human activities.