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Why does Asia have the longest coastline of any continent?

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A map of the continent of Asia, including its countries, boundaries, and capital cities, as well as parts of Europe, Africa, and surrounding oceans. — Asia Map showing the countries and national capitals of Asia.

Asia possesses the longest coastline of any continent primarily due to its immense size and its highly irregular coastal geography. Unlike the relatively regular coastal boundaries found on the eastern side of the Pacific, the western, or Asiatic, coastal boundary is characterized by numerous marginal seas, including the Sea of Okhotsk, the Sea of Japan, the Yellow Sea, the East China Sea, and the South China Sea.12

This complexity is further increased by the presence of southward-jutting peninsulas and various island arcs that form the eastern boundaries of these seas. Additionally, Asia is a structurally complicated and geologically active continent where new land is continuously produced and added to the mainland through the episodic collision of these island arc systems. This combination of vast scale and intricate, indented coastal features results in the longest coastline on Earth.21