History of the Supercontinent Pangea

Pangea (alternative spelling: Pangaea) was a supercontinent that existed on the Earth millions of years ago, covering about one-third of its surface. A supercontinent is a large landmass comprised of multiple continents. In the case of Pangea, nearly all of the Earth's continents were connected into a single landform. Most people believe that Pangea began developing over 300 million years ago, was fully formed 270 million years ago, and separated around 200 million years ago.

The name Pangea comes from an ancient Greek word meaning "all lands." This term was first used in the early 20th century when Alfred Wegener noticed that the Earth's continents seemed to fit together like a jigsaw puzzle. He later developed the theory of continental drift to explain the shapes and positions of continents and coined the title Pangea at a symposium in 1927 on the topic. This theory evolved over time into the modern study of plate tectonics.

Formation of Pangea

Pangea was formed through years and years of landmass formation and movement. Mantle convection within the Earth's surface millions of years ago caused new material to constantly come to the surface between the Earth's tectonic plates at rift zones. These masses or continents then moved away from the rift as new material surfaced. Continents eventually migrated toward one another to combine into one supercontinent and it was in this way that Pangea was born.

But how exactly did these landmasses join? The answer is through a lot of migration and collision. Around 300 million years ago, the northwestern part of the ancient continent of Gondwana (near the South Pole) collided with the southern part of the Euramerican continent to form one massive continent. After a while, the Angaran continent (near the North Pole) began to move south and merged with the northern part of the growing Euramerican continent, forming the supercontinent that came to be known as Pangea. This process concluded about 270 million years ago.

There was only one landmass separate from Pangea remaining, Cathaysia, and it was made up of north and south China. It never became part of the supercontinent. Once completely formed, Pangea covered around one-third of the Earth's surface and the rest was ocean (and Cathaysia). This ocean was collectively called Panthalassa.

Division of Pangea

Pangea began to break up about 200 million years ago in the same way that it was formed: through tectonic plate movement caused by mantle convection. Just as Pangea was formed through the movement of new material away from rift zones, new material also caused the supercontinent to separate. Scientists believe that the rift that would ultimately divide Pangea began due to a point of weakness in the Earth's crust. At that weak area, magma surfaced and created a volcanic rift zone. Eventually, this rift zone grew so large that it formed a basin and Pangea started to dissociate.

Ocean Formation

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Distinct oceans were formed as Panthalassa occupied newly-opened areas of the landmass. The first ocean to form was the Atlantic. About 180 million years ago, a portion of the Atlantic Ocean opened up between North America and northwestern Africa. Around 140 million years ago, the South Atlantic Ocean formed when today's South America separated from the west coast of southern Africa.

The Indian Ocean emerged when India separated from Antarctica and Australia. About 80 million years ago, North America and Europe, Australia and Antarctica, and India and Madagascar followed suit and separated. Over millions more years, the continents moved to their approximate current positions.

For a diagram of Pangea and its path of separation, visit the United States' Geological Survey's Historical Perspective page within This Dynamic Earth.

Evidence for Pangea

Not everyone is convinced that Pangea ever existed, but there is plenty of evidence that experts use to prove that it did. The strongest support has to do with how the continents fit together. Other evidence for Pangea includes fossil distribution, distinctive patterns in rock strata spread out all around the world, and the global placement of coal.

Continents Fitting Together

As Alfred Wegener—creator of the continental drift theory—noticed in the early 20th century, the Earth's continents seemed to fit together like a jigsaw puzzle. This is the most significant evidence for Pangea's existence. The most prominent place where this is visible is along the northwestern coast of Africa and the eastern coast of South America. In these locations, the two continents look like they could have been connected at one point, and many believe that they were in the time of Pangea.

Fossil Distribution

Archaeologists have found matching fossil remains of ancient terrestrial and freshwater species in continents now separated by thousands of miles of ocean. For example, matching freshwater reptile fossils have been found in Africa and South America. Because crossing the Atlantic Ocean would have been impossible for these saltwater-averse creatures, their fossils indicate that the two continents must have once been connected.

Rock Patterns

Patterns in rock strata are another indicator of the existence of Pangea. Geologists have discovered distinctive patterns in rocks on continents nowhere near each other. Coastal configurations were the first marker to point to a jigsaw puzzle-like continent layout years ago, then geologists were further convinced of Pangea's existence when they discovered that even rock layers on the continents that appear to have once fit together match each other exactly. This indicates that continents must have grown apart as identical rock stratification couldn't have been a coincidence.

Coal Placement

Finally, the world's coal distribution is evidence for Pangea in much the same way that fossil distribution is. Coal normally forms in warm, wet climates. However, scientists have found coal under Antarctica's frigid, dry ice caps. For this to be possible, it is believed that the icy continent was previously in another location on the Earth and had a very different climate—which had to have been supportive of coal formation—from today.

More Supercontinents

Based on evidence that has emerged through the study of plate tectonics, it is likely that Pangea was not the only supercontinent to have existed. In fact, archaeological data found through matching rock types and searching for fossils shows that the formation and destruction of supercontinents like Pangea probably happened again and again throughout history. Gondwana and Rodinia are two supercontinents that scientists support the existence of that were probably around prior to Pangea.

Scientists predict that supercontinents will continue to appear. Today, the world's continents are slowly moving away from the Mid-Atlantic Ridge toward the middle of the Pacific Ocean. It is believed that they will eventually collide with one another in about 80 million years.

Sources

• Kious, W. Jacquelyne, and Robert I. Tilling. “The Story of Plate Tectonics.” This Dynamic Earth, United States Geological Survey, 30 Nov. 2016.
• Lovett, Richard A. “Texas and Antarctica Were Attached, Rocks Hint.” National Geographic News, National Geographic, 16 Aug. 2011.