Where the continent ends

Abstract The Earth's continents and islands are bordered by shallow ocean plains that are arguably the most environmentally, economically, and politically important parts of the sea. Yet in spite of this, they remain poorly defined and understood. A quantitative approach is employed here to map and analyze these plains, or shelves. The Earth's ocean bathymetry was used to determine the continent‐ocean basin transition at ~1200 m and then parsed with a novel geospatial terrain classification concept/method borrowed from the field of image analysis: the geomorphic phonotype, or geomorphon. The technique is less subjective than visual interpretation and digitization and here illustrates that the ocean coastal plains are deeper, wider, and more steeply sloped than previously recognized. Their variable form is related to tectonics and latitude and ultimately affects function and habitat.