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Why are continental shelves narrow off mountainous coasts?

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continental shelf The broad, gentle pitch of the continental shelf gives way to the relatively steep continental slope. The more gradual transition to the abyssal plain is a sediment-filled region called the continental rise. The continental shelf, slope, and rise are collectively called the continental margin.

Continental shelves are narrow off mountainous coasts primarily because these regions are typically located on tectonically active continental margins, such as the leading edges of tectonic plates.21

In these settings, the shelf is often a direct continuation of the steep, rugged topography of the adjacent landmass. Unlike passive margins—which are characterized by broad coastal plains and thick accumulations of sediment—mountainous coasts are often associated with subduction zones or other active tectonic processes that result in steep, deformed slopes. Because these margins are tectonically active and often lack the extensive, flat coastal plains that allow for broad sediment deposition, the shelf remains narrow, steep, and relatively rough.231