The Lost Worlds of Planet Earth Ortelius hypothesized the idea that land masses may have been connected in the past, Alfred Wegener who hypothesized the idea of a super-continent Pangaea and continental drift despite the prevailing idea of flooded land-bridges at the time, and Bruce C. Heezen and Marie Tharp who discovered the Mid-Atlantic Ridge that supported the theory of plate tectonics. Tyson describes how the landmasses of the earth lay atop the mantle, which moves due to the motion and heat of the earth's outer and inner core. Tyson moves on to explain the asteroid impact that initiated the Cretaceous–Paleogene extinction event, leaving small mammals
Naming of the Americas unitary continent, the form is generally "the continent of America" in the singular. However, without a clarifying context, singular "America" in English commonly refers to the United States of America. The earliest known use of the name "America" dates to April 25, 1507, where it was applied to what is now known as South America. It appears on a small globe map with twelve time zones, together with the largest wall map made to date, both created by the German cartographer Martin Waldseemüller in Saint-Dié-des-Vosges in France. These were the first maps to show the Americas as a land mass