Why does the Arctic Ocean have such wide continental shelves near Eurasia?

The Arctic Ocean is unique because nearly one-third of its total area is underlain by continental shelf, which is distributed asymmetrically around its circumference. While continental shelves typically average about 40 miles in width, the shelves off the Eurasian coast—specifically the Siberian and Chukchi shelves—are exceptionally broad, ranging from 300 to 1,100 miles in width.123

The primary reason for this variation is that continental shelves are generally a continuation of the continental landmass; they tend to be narrow and steep off mountainous coasts but broad and comparatively level offshore from plains. The vast Eurasian sector of the Arctic is characterized by these extensive, low-lying plains, which contribute to the development of such wide shelves. Additionally, these broad areas are divided into five main marginal seas—the Barents, Kara, Laptev, East Siberian, and Chukchi seas—which occupy a significant portion of the Arctic Ocean's area.32