Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and comprises 30% of its land area. With approximately 4.3 billion people, it hosts 60% of the world's current human population. Asia has a high growth rate in the modern era. For instance, during the 20th century, Asia's population nearly quadrupled. The boundaries of Asia are culturally determined, as there is no clear geographical separation between it and Europe, which together form one continuous landmass called Eurasia. The most commonly accepted boundaries place Asia to the east of the Suez Canal, the Ural River, and the Ural Mountains, and south of the Caucasus Mountains and the Caspian and Black Seas. It is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean and on the north by the Arctic Ocean.