Asia is considered the world's largest continent. It covers 44, 579,000 square kilometers of Earth's total land area and 8.7% of the Earth's total surface area. It has the majority of the human population. To the east is the pacific ocean, the south Indian Ocean, and the northern Arctic Ocean. Asia, Africa, and Europe are physically and geologically connected at the northwest end. Asia holds the largest economy in the world. The silk road became Asia's main source of income and economic growth. This led to Asia, during the 20th century, spiking in population growth.