That's what scientists believe. They think that, about 270 million years ago, almost all of the land on Earth was part of one supercontinent. Today, scientists refer to that former supercontinent as Pangaea, which comes from a Greek word that means “all the Earth."
Scientists theorize that Pangaea began to split apart around 200 million years ago. Over time, the separate pieces drifted farther and farther apart, creating the continents we know today. The movement of the continents also created the Atlantic and Indian Oceans.
Of course, we don't have any records or photographs from that long ago. So the existence of Pangaea is just a theory. In fact, it was German meteorologist Alfred Wegener who first proposed the idea of Pangaea way back in 1912 as part of his theories about how continents drift.
Wegener's theories have since been replaced by a more modern understanding of plate tectonics. Scientists, who have studied how the ocean floor spreads apart, believe that Pangaea broke apart slowly in several stages rather than all at once.
Scientists who have studied plate tectonics think that Pangaea wasn't the only supercontinent in Earth's past. Modern theories hold that a supercontinent called Rodinia existed a billion years ago and another supercontinent named Pannotia formed about 600 million years ago.
Plate tectonic theories tell scientists that the Earth's crust is made up of various plates that continue to move even today. For example, scientists believe the continents are moving together again, albeit extremely slowly.
Followers of plate tectonic theories believe Africa is colliding with southern Europe and Australia is colliding with Southeast Asia. A new Pangaea could form within the next 50 million years when Africa and Australia merge with Europe and Asia! This assembly and subsequent break-up of Earth's landmasses is known as the supercontinent or Wegenerian cycle.
How do scientists know all this? They make educated guesses about what might have happened millions of years ago based upon evidence they find today. For example, scientists have found fossils from identical species on continents that are now far apart.
Geological evidence also gives scientists clues as to how Pangaea formed and subsequently broke apart. For example, scientists have found matching geological trends on both the eastern coast of South America and the western coast of Africa, leading them to believe these two landmasses must have been joined together at one time.