The fourth-largest continent on earth, South America is a land of great extremes. The longest mountain range on the planet, the world's highest active volcano, the world's highest waterfall, and the world's driest region all lie with its boundaries. South America's chief river, the 3,900-mile-long Amazon, and its more than 1,000 tributaries flow from the world's largest drainage basin, which is home to countless animal and plant species.