What was pangaea called before

Scotland was at the apex of the Labrador-Greenland promontory. When nestled electronically in the Arica embayment, the rocks of the Scottish Highlands that I studied for my doctoral degree in the s appear to continue into equally old rocks of Peru and Bolivia.

Given how well studied the Scottish Highlands are, they may provide critical tests for a former North America-South America connection. Assuming the SWEAT hypothesis and the Pan-American connection, we can try to reconstruct the global distribution of continents and oceans in the late Precambrian.

Most geologists believe that the relative areas occupied by continents and ocean basins have not changed since the late Precambrian. If, therefore, Antarctica, Australia, North America and fragments of South America were fused into a pre-Pangaean supercontinent, now named Rodinia, then there had to have been vast oceans elsewhere. Ophiolitic relics caught up within the continents indicate that these oceans lay between India and today's East Africa the Mozambique Ocean and within Africa and South America the Pan-African and Braziliano oceans, respectively.

Between roughly million and million years ago these ocean basins were destroyed, and all the Precambrian nuclei of Africa, Australia, Antarctica, South America and India amalgamated into the supercontinent of Gondwana. It was during this time interval that the Pacific Ocean basin opened between Laurentia and the East Antarctic-Australian landmass.

Isotopic dating of volcanic rocks in Newfoundland shows that the ocean basin between Laurentia and South America did not open until the beginning of the Cambrian.

North America may therefore have separated out in a two-stage process. Reconstructing the travels of North America requires an essential piece of information: the magnetization of ancient rocks. Such data allow geologists to figure out the latitude and orientation of the rocks when they formed. But because Earth's magnetic field is axially symmetrical, paleomagnetic measurements cannot tell us about the original longitude of the rocks. Present-day lava from Iceland and Hawaii, for example, could reveal to a geologist million years from now the latitudes and the orientation of these islands but not their vast difference in longitude.

It would not be apparent that the islands are in different oceans. Traditional reconstructions of Laurentia always place its Appalachian margin opposite northwestern Africa during the Paleozoic era. I decided to plot the relation of North America to Gondwana differently, taking advantage of the fact that the longitude of the continent is not constrained by paleomagnetic data.

It turned out that North America could have made what one of my graduate students referred to as an "end run" around South America during the Paleozoic, starting from next to Antarctica. When Luis H. Dalla Salda, Carlos A. Cingolani and Ricardo Varela of the University of La Plata in Argentina saw the sketch of the end run, they became excited. They had recently proposed that a Paleozoic mountain belt, whose roots are exposed in the Andes of northern Argentina, could have formed when another continent collided with Gondwana.

Moreover, the western margin of this Famatinian belt includes Cambrian and Lower Ordovician limestones between million and million years old containing trilobites characteristic of North America. Perhaps, they reasoned, this is a "geologic calling card" left behind when North America collided with South America during the Ordovician period, million years ago. It appears that after rifting from South America at the end of the Precambrian, North America moved quite far away.

During the Cambrian period, when Gondwana was undergoing glaciation, North America was equatorial. Ocean floor was then subducted beneath the South American craton, and North and South America collided again during the Ordovician. We think that the older part of the Appalachian Mountains, which terminates abruptly in Georgia, was once continuous with Argentina's Famatinian belt.

This construction places Washington, D. My Argentine colleagues and I have suggested that these rocks tore off the ancestral Gulf of Mexico, known as the Ouachita embayment. Blocks carried up by Andean volcanoes from below the limestones have recently been dated at around one billion years old, just like those of the Grenville province that probably occupied the embayment. It is possible that the North and South American continents interacted again before North America finally collided with northwestern Africa to complete Pangaea.

French geologists studying the Paleozoic sedimentary rocks of the Peruvian Andes have found that they are made of debris that must have eroded from a neighboring landmass. They assumed this continent, occupying the area now covered by the Pacific Ocean, to have been an extension of the Arequipa massif in Peru. It may, however, have been North America. As Heinrich Bahlburg of the University of Heidelberg in Germany has pointed out, ancient warm-water North American fauna mingle with cold-water fauna of southern Africa and the Falkland Malvinas Islands in the million-year-old Devonian strata of northwestern South America.

Together with a deformation along the eastern seaboard of North America known as the Acadian orogeny, and the truncation of mountain structures along the South American margin, the evidence points to Laurentias sideswiping northwestern South America during the Devonian.

There are even Ordovician limestones with South American trilobites--another calling card--at Oaxaca in Mexico. Only after North America finally moved away from the proto-Andean margin did the Andean Cordillera of the present day begin to develop. Some million years later North America returned to collide with northern Europe, Asia and Gondwana. Pangaea--with the Urals, the Armorican Mountains in Belgium and northern France, the Ouachitas and the youngest Appalachians as sutures--arose from the collisions of these continents.

After a million-year odyssey, North America had finally found a resting place. But not for long. In another 75 million years it separated from Africa as Pangaea broke up, to move toward its current position. During the southern summer of six years after my first glimpse of the Pensacola Mountains and glimmerings of North America''s odyssey--I returned to Antarctica. This time, with my colleague Mark A.

According to my computer simulations, this is where North Americas Grenville rocks had projected million years ago. Antarctic geologists have long regarded these areas as anomalous. At the end of our visit to Coats Land, we roped together, picked up our ice axes and climbed back to another small aircraft. Weighing down our packs--and the aircraft, which groaned into the air--were the rock samples we had gleaned that day. In the laboratories of my colleagues Wulf A.

Gose and James N. Connelly, we sat down to analyze those rocks. They offered the first testable hypothesis regarding global geography in late Precambrian and early Paleozoic times--the critical era when single-celled organisms evolved into soft-bodied multicellular creatures, then invertebrates with hard shells and, ultimately, primitive vertebrates. Over the past decade, interest in the Rodinian supercontinent that preceded Pangaea has spawned research centers and international programs to study this supercontinents assembly, geography and fragmentation.

One related result of this scientific ferment is the "snowball Earth" hypothesis, which proposes that Earth was covered with ice at sea level all the way to the equator million to million years ago, at the time of Rodinias fragmentation and the formation of the Pacific Ocean basin. The snowball Earth hypothesis posits an extreme global environment that challenges our understanding of climate past, present and future. If confirmed, it would mean that a dramatically chilly period directly preceded the explosion of multicellular life that occurred approximately million years ago.

Because forecasters rely on the distribution of continental landmasses in designing computer climate models, our rather esoteric study of ancient supercontinents has clearly taken on added significance in recent years. With the absence of ocean floor predating Pangaea and the fragmentary nature of evidence from the continents, opinions regarding this period of Earth history inevitably differ.

Some experts even doubt the very existence of the late Precambrian Rodinian supercontinent described in this article--doubts difficult to reconcile with the thousands of kilometers of preserved late Precambrian rifted continental margins.

Other researchers have used the same data we have relied on to reach radically different notions of the way this pre-Pangaean supercontinent may have looked.

Instead of a connection between the southwestern U. Southwest and Mexico were connected to southeastern Australia. Scientists believe that Pangea broke apart for the same reason that the plates are moving today. The movement is caused by the convection currents that roll over in the upper zone of the mantle. This movement in the mantle causes the plates to move slowly across the surface of the Earth. About million years ago Pangaea broke into two new continents Laurasia and Gondwanaland.

Gondwanaland was made of the present day continents of Antarctica, Australia, South America. The subcontinent of India was also part of Gondwanaland. Notice that at this time India was not connected to Asia. The huge ocean of Panthalassa remained but the Atlantic Ocean was going to be born soon with the splitting of North America from the Eurasian Plate. How do we know that South America was attached to Africa and not to North America million years ago? Scientists today can read the history of the rock record by studying the age and mineral content of the rocks in a certain area.

The Triple Junction was formed because of a three-way split in the crust allowing massive lava flows. The split was caused by an upwelling of magma that broke the crust in three directions and poured out lava over hundreds of square miles of Africa and South America. The rocks of the triple junction, which today is the west central portion of Africa and the east central portion of South America, are identical matches for age and mineral make up.

In other words the rocks in these areas of the two continents were produced at the same time and in the same place. This tells us that South America and Africa were connected at one time! Today these two continents are separated by the Atlantic Ocean which is over miles wide! About million years ago Laurasia was still moving, and as it moved it broke up into the continents of North America, Europe and Asia Eurasian plate.

Gondwanaland also continued to spread apart and it broke up into the continents of Africa, Antarctica, Australia, South America, and the subcontinent of India.

Arabia started to separate from Africa as the Red Sea opened up. The red arrows indicate the direction of the continental movements.

Notice how far the Indian subcontinent has to move to get to its present postion connected to Asia. The Atlantic, Indian, Arctic, and Pacific Oceans are all beginning to take shape as the continents move toward their present positions. The plates are still moving today making the Atlantic Ocean larger and the Pacific Ocean smaller.

The yellow arrows on the world map indicate the direction of plates movements today. Notice the position of the Indian Subcontinent today. It moved hundreds of miles in million years at a great speed 4 inches per year!!! The Indian plate crashed into the Eurasian plate with such speed and force that it created the tallest mountain range on Earth, the Himalayas! What do you predict the world will look like in million or million years?

And about million years ago some of the earliest dinosaurs emerged on Pangaea, including theropods, largely carnivorous dinosaurs that mostly had air-filled bones and feathers similar to birds. The current configuration of continents is unlikely to be the last. Supercontinents have formed several times in Earth's history, only to be split off into new continents. Right now for instance, Australia is inching toward Asia, and the eastern portion of Africa is slowly peeling off from the rest of the continent.

Geologists have noticed that there is a quasi-regular cycle in which supercontinents form and break up every to million years, but exactly why is a mystery, Murphy said. But most scientists believe that the supercontinent cycle is largely driven by circulation dynamics in the mantle, according to a article in the Journal of Geodynamics.

Beyond that, the details get fuzzy. While the heat formed in the mantle likely comes from the radioactive decay of unstable elements, such as uranium, scientists don't agree on whether there are mini-pockets of heat flow within the mantle, or if the entire shell is one big heat conveyor belt, Murphy said.

Scientists have created mathematical, 3D simulations to better understand the mechanisms behind continental movement. Santhosh explain how they produced simulations of large-scale continental movements since the breakup of Pangaea million years ago. The models show how tectonic plate motion and mantle convection forces worked together to break apart and move large land masses.

For example, Pangaea's large mass insulated the mantle underneath, causing mantle flows that triggered the initial breakup of the supercontinent. Radioactive decay of the upper mantle also raised the temperature, causing upward mantle flows that broke off the Indian subcontinent and initiated its northern movement. Yoshida and Santos created additional geological models to predict mantle convection and continental movement patterns million years in the future.

These models suggest that over millions of years, the Pacific Ocean will close as Australia, North America, Africa, and Eurasia come together in the Northern Hemisphere. Eventually, these continents will merge, forming a supercontinent called "Amasia. Tia is the assistant managing editor and was previously a senior writer for Live Science. Her work has appeared in Scientific American, Wired.