The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America. When viewed as a single continent, the Americas are the 2nd largest continent by area after Asia and the 3rd largest continent by population. The Americas make up most of the land in Earth's Western Hemisphere and constitute the New World.
Along with their associated islands, the Americas cover 8% of Earth's total surface area and 28.4% of its land area. The topography is dominated by the American Cordillera, a long chain of mountains that runs the length of the west coast. The flatter eastern side of the Americas is dominated by large river basins, such as the Amazon, St. Lawrence River–Great Lakes, Mississippi, and La Plata basins. Since the Americas extend 14,000 km (8,700 mi) from north to south, the climate and ecology vary widely, from the arctic tundra of Northern Canada, Greenland, and Alaska, to the tropical rainforests in Central America and South America.
