The terms also apply to large areas of land. Because mountain-building (orogeny) lifts up huge sections of the Earth, there are large areas which are well above sea level: the highlands. But on the trailing edge of a continent, the land is low. So the Americas are (broadly speaking) high on the west (the American Cordillera) and low on the east (Amazon, St. Lawrence River / Great Lakes basin, Mississippi, and La Plata). This is a consequence of plate tectonics, as the Americas have moved slowly west for over 100 million years. The Appalachians are a far older chain of ground-down mountains carried along by the continent as it moved west.