Pangea

Pangea, also spelled Pangaea, 

Pangea [Credit: Adapted from C.A. Ross and J.R.P. Ross, Cushman Foundation for Foraminiferal Research, Special Publication 24]in early geologic time, a supercontinent that incorporated almost all the landmasses on Earth.

continental drift [Credit: Encyclopædia Britannica, Inc.]Pangea was surrounded by a global ocean called Panthalassa, and it was fully assembled by the Early Permian Period (some 299 million to 272 million years ago). The supercontinent began to break apart about 200 million years ago, during the Early Jurassic Period (201 million to 174 million years ago), eventually forming the modern continents and the Atlantic and Indian oceans. Pangea’s existence was first proposed in 1912 by German meteorologist Alfred Wegener as a part of his theory of continental drift. Its name is derived from the Greek pangaia, meaning “all the Earth.”

 

During the Early Permian, the northwestern coastline of the ancient continent Gondwana (a paleocontinent that would eventually fragment to become South America, India, Africa, Australia, and Antarctica) collided with and joined the southern part of Euramerica (a paleocontinent made up of North America and southern Europe). With the fusion of the Angaran craton (the stable interior portion of a continent) of Siberia to that combined landmass during the middle of the Early Permian, the assembly of Pangea was complete. Cathaysia, a landmass comprising the former tectonic plates of North and South China, was not incorporated into Pangea. Rather, it formed a separate, much smaller, continent within the global ocean Panthalassa.

The mechanism for the breakup of Pangea is now explained in terms of plate tectonics rather than Wegener’s outmoded concept of continental drift, which simply stated that Earth’s continents were once joined together into the supercontinent Pangea that lasted for most of geologic time. Plate tectonics states that Earth’s outer shell, or lithosphere, consists of large rigid plates that move apart at oceanic ridges, come together at subduction zones, or slip past one another along fault lines. The pattern of seafloor spreading indicates that Pangea did not break apart all at once but rather fragmented in distinct stages. Plate tectonics also postulates that the continents joined with one another and broke apart several times in Earth’s geologic history.

The first oceans formed from the breakup, some 180 million years ago, were the central Atlantic Ocean between northwestern Africa and North America and the southwestern Indian Ocean between Africa and Antarctica. The South Atlantic Ocean opened about 140 million years ago as Africa separated from South America. About the same time, India separated from Antarctica and Australia, forming the central Indian Ocean. Finally, about 80 million years ago, North America separated from Europe, Australia began to rift away from Antarctica, and India broke away from Madagascar. India eventually collided with Eurasia approximately 50 million years ago, forming the Himalayas.

During Earth’s long history, there probably have been several Pangea-like supercontinents. The oldest of those supercontinents is called Rodinia and was formed during Precambrian time some one billion years ago. Another Pangea-like supercontinent, Pannotia, was assembled 600 million years ago, at the end of the Precambrian. Present-day plate motions are bringing the continents together once again. Africa has begun to collide with southern Europe, and the Australian Plate is now colliding with Southeast Asia. Within the next 250 million years, Africa and the Americas will merge with Eurasia to form a supercontinent that approaches Pangean proportions. The episodic assembly of the world’s landmasses has been called the supercontinent cycle or, in honour of Wegener, the Wegenerian cycle (see plate tectonics: Supercontinent cycle).