When was pangea broke

From Ms Jeannie Cooper October Reply by Dr Ted Nield Editor, Geoscientist I cannot fault your arithmetic, and you reach a conclusion that is not, in fact, far from the truth - though the scale of the answer is perhaps a little exaggerated.

Pangaea began to break up about million years ago. However it was only the latest in a long series of supercontinents to form on Earth as the drifting continents came together repeatedly in a cycle that lasts about million years from end to end.

So at the moment we are half way through the present cycle. In another million years a new supercontinent will form. Supercontinents hold together for roughly million years — hence part of the inherent exaggeration in your equation. Also, spreading rates vary enormously from about 1cm per year at the slowest Gakkel Ridge, Arctic Ocean to as much as 15cm per year East Pacific Rise. Before Pangaea, at about million years ago, another supercontinent occupied equatorial regions and has been called Rodinia.

There has been a succession of such cycles since plate tectonics first began, shortly after the formation of the earth million years ago - though of course the farther back one goes, the dimmer the light that the rock record sheds. 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. Distinct oceans were formed as Panthalassa occupied newly-opened areas of the landmass. The first ocean to form was the Atlantic.

About million years ago, a portion of the Atlantic Ocean opened up between North America and northwestern Africa. Around million years ago, the South Atlantic Ocean formed when today's South America separated from the west coast of southern Africa.

Over millions more years, the continents moved to their approximate current positions. 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. 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. 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.

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. In fact, millions years ago the Earth's seven continents were all grouped together into a supercontinent called Pangea. Just before the days of the dinosaurs the Earth's continents were all connected into one huge landmass called Pangaea.

This huge supercontinent was surrounded by one gigantic ocean called Panthalassa. Notice the postion of the continents of Antarctica Far north of its current position , Australia flipped sideways and far west of its current position and the subcontinent of India Hundreds of miles from Asia. Scientists believe that the North American continent was located much farther south and east of it's position today.

In fact, much of North America was in or near the tropics!! How do scientists know this?? They have found fossils from this period of time. These fossils are of tropical plants and animals. The fossils have been found in cold regions like North Dakota and Greenland!!! About million years ago the supercontinent Pangea began to break up. 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. These basin deposits are part of a sequence of rocks know as the Newark Supergroup, with thicknesses reaching up to 6 km in some places.

There are more Triassic rift basins located off the east coast that are buried by continental shelf sediments Figure 1. During the Jurassic, the final break between the plates of North America, Africa and Baltica occurred many kilometers to the east of today's coastline at what is now the Mid-Atlantic Ridge. Other fragments of Pangea gradually broke into the modern continents, slowly moving into their present positions over the next several hundred millions of years.

The tension released by the pulling apart of plates, resulted in numerous faults and volcanoes. Alternating with the sandstone and shale being deposited in the basins were deposits of ash and lava flows originating from volcanoes along the rift area.

The flay-lying beds of the Newark and Connecticut Valley basins were eventually faulted again and tilted, exposing the edges of the layers of sediment and cooled lava. The hardened lava was more resistant to the erosion that the sediments in the basin, so ridges of cooled lava were left standing as the sediments around them wore away Figure 1. Some rocks wear down relatively quickly, while others can withstand the power of erosion for much longer.