What is Pangea?

Pangea comes from the ancient Greek word for "all lands." Alfred Wegener coined the term in 1927. Wegener noticed that the composition of coal deposits in Pennsylvania was the same as coal deposits in Poland, Great Britain and Germany. This convinced Wegener that North America and Europe must have been a single landmass at one time.

Once scientists in fields, such as biology, chemistry, geology, and anthropology, realized the continents must have been connected at one point, they wanted to know how the great separation happened. This led to the study of plate tectonics and the theory of continental drift. "Tectonics" is based on the Greek word meaning "to build." The term "plate" in geology refers to a large slab of solid rock.

The Earth's surface isn't a huge, solid shell. It is composed of multiple slabs that move and collide with each other. The slabs are tectonic plates, and they move by sliding across the Earth's mantle. The mantle is the super-heated, semi-solid material making up the earth's interior. When volcanoes erupt, the magma comes from the Earth's mantle. The mantle is approximately 2,900 kilometers, or 1,802 miles, thick and makes up 84% of the Earth's total mass.

The large tectonic plates that form the continents move away from rift zones. Rift zones are weakened areas of the Earth's crust that allow material from the mantle to come to the Earth's surface and split large land masses. The Great Rift Valley in Kenya offers a chance to observe a rift zone in action, without molten material. Houses and roads are collapsing as the Great Rift Valley expands and the edges slowly pull away from each other.

We wouldn't expect the bones of panda bears that live in Asia to be found next to bones of gazelles or zebras from Africa. The continents are too far apart. Archaeologists have found fossils of similar or identical plant and animal species on different continents. There were no zoos or human-cultivated crops or trees that could have explained the presence of the same fossils on different continents. Models of Pangea display Africa, North America, and Asia sharing borders within Pangea. The fossils are on different continents now, but the animals and plants were on the same landmass in life.

Mountain chains such as the Swiss Alps and the Appalachian Mountains in the United States were once continuous chains. Those mountains are thousands of miles apart now. It seems impossible that they were ever connected, but geologists have matched rock formations and composition on on different continents. Images of the edges of mountain chains and individual rock formations can be placed side by side, and it is obvious that they were once connected. The western coast of Africa and the eastern coast of South America look like they could merge perfectly.

One huge landmass had a very different climate than the current separated continents. The interior of Pangea may have been very dry since it was behind massive mountain chains. Coal deposits in the United States and Europe show that some parts of the interior continent had to be covered in dense vegetation. Coal is created when dead plants and animals sink into swamp water. Pressure and water eventually change the material into peat, and peat becomes coal. There are a limited set of conditions that allow coal to form, so we know that conditions on many of our continents were once very different than they are now.

One of Earth's most thorough extinction events happened during the time of Pangea. The Permian-Triassic extinction or the "Great Dying" may have been the most massive extinction event Earth ever experienced. Approximately 96% of marine species and 70% of terrestrial species died out completely. The cause of the Great Dying isn't known, but most scientists believe it was caused by volcanic eruptions or global warming. Both events end with the same ultimate outcome. Life in the oceans, plant, and animal, suffocated. Terrestrial life breathed air filled with toxins and very little oxygen. Plant life on land couldn't survive. Life in the oceans has complex effects on the planet as a whole. A significant percentage of oxygen in the atmosphere comes from the oceans. Scientists don't believe life on Earth as it is now could survive a massive die-out of marine life.

One of the strongest pieces of evidence for Pangea is the fascinating array of fossils and other observations scientists discovered in Antarctica. The remains of lush vegetation exist under the ice covering the frozen continent. There are lakes filled with life underneath the ice as well. Antarctica once had a warm, wet, tropical climate. There is still much to discover in Antarctica. Although the discoveries are exciting and providing clues to Earth's past, they are only possible because the ice of Antarctica is thinning.

Pangea was only the most recent supercontinent. Scientists believe that supercontinents have formed and broken apart at least seven times. Pangea was preceded by the supercontinent Rodinia. Rodinia was formed after the break-up of Pannotia, and Panthalassa may have formed from part of the Pan-African superocean surrounding the V-shaped supercontinent Pannotia. The shapes and structure of supercontinents before Pangea are theorized, but they are not known with certainty. The forces that bring supercontinents together and tear them apart destroyed many clues related to structure of previous supercontinents.