How wide is the average continental shelf?

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The average width of a continental shelf is approximately 65 to 75 km (about 40 to 45 miles).12

Because continental shelves are essentially extensions of the continental landmass beneath the ocean, their width varies significantly depending on the adjacent coastal geography. They tend to be narrow and steep off mountainous coasts, such as the western coast of the United States, where they may measure only about 32 km (20 miles) wide. Conversely, they are typically broader and more level offshore from plains, with some regions extending more than 120 km (75 miles). The world's largest continental shelf is found off the coast of Siberia, extending up to 1,500 km (about 930 miles) into the Arctic Ocean.12