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How wide is a typical continental shelf?

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Map graphic showing the boundaries of the five oceans-Pacific, Atlantic, Indian, Arctic, and Southern-using color-coded regions. Four different map projections are included: North Pole view, South Pole view, International Date Line view, and Greenwich Meridian view, each displaying the oceans' extents around the continents. — ocean Earth's oceans and their marginal seas cover nearly 71 percent of the planet's surface.

The width of a continental shelf varies significantly depending on the location and the nature of the adjacent coastline. While the average width is approximately 65 to 75 km (40 to 45 miles), these features are highly variable.12

The shelf is typically narrow—sometimes measuring only about 32 km (20 miles)—off mountainous coasts where crustal plates converge, such as along the western coast of the United States. Conversely, shelves are generally broader and more level offshore from plains, often extending well beyond 120 km (75 miles). Exceptionally wide shelves exist in various parts of the world, with the largest extending 1,500 km (about 930 miles) from the coast of Siberia into the Arctic Ocean.12