Everything about Pangaea totally explained
Pangaea,
Pangæa or
Pangea (from παν,
pan, meaning
entire, and Γαῖα,
Gaea, meaning
Earth in
Ancient Greek) was the
supercontinent that existed during the
Paleozoic and
Mesozoic eras about 250 million years ago, before each of the component
continents were separated into their current configuration .
The name was first used by the
German originator of the
continental drift theory,
Alfred Wegener, in the 1920 edition of his book
The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane), in which a postulated supercontinent Pangaea played a key role.
Configuration of Pangaea
Paleogeographic reconstructions show Pangaea as a C-shaped landmass that was spread across the
equator. The
body of water that was enclosed within the resulting crescent has been named the
Tethys Sea. Owing to Pangaea's massive size, the inland regions appear to have been very dry. The large supercontinent would potentially have allowed terrestrial animals to migrate freely.
The vast ocean that surrounded the
supercontinent of Pangaea has been named
Panthalassa. The break-up of Pangaea began about 180 million years ago (180
mya) in the
Jurassic Period, first into two supercontinents (
Gondwana to the south and
Laurasia to the north), thereafter into the
continents we've today.
Formation of Pangaea
Rodinia, which formed 1.1 billion years ago during the
Proterozoic, was the supercontinent from which all subsequent continents, sub or super, derived. Rodinia doesn't preclude the possibility of
prior supercontinents as the breakup and formation of supercontinents appears to be
cyclical through Earth's 4.6 billion years.
Gondwana followed with several iterations before the formation of Pangaea, which succeeded
Pannotia, before the beginning of the
Paleozoic Era (545 Ma) and the
Phanerozoic Eon.
The minor supercontinent of
Proto-Laurasia drifted away from Gondwana and moved across the
Panthalassic Ocean. A new ocean was forming between the two continents, the
Proto-Tethys Ocean. Soon, Proto-Laurasia drifted apart itself to create
Laurentia,
Siberia and
Baltica. The rifting also spawned two new oceans, the
Iapetus and
Khanty Oceans. Baltica remained east of Laurentia, and Siberia sat northeast of Laurentia.
In the
Cambrian the independent continent of
Laurentia on what would become
North America sat on the
equator, with three bordering oceans: the
Panthalassic Ocean to the north and west, the
Iapetus Ocean to the south and the
Khanty Ocean to the east. In the Earliest
Ordovician, the microcontinent of
Avalonia, a landmass that would become the northeastern
United States,
Nova Scotia and
England, broke free from Gondwana and began its journey to
Laurentia.
Baltica collided with Laurentia by the end of the Ordovician, and northern Avalonia collided with Baltica and Laurentia. Laurentia, Baltica and Avalonia formed to create a minor supercontinent of
Euramerica or Laurussia, closing the Iapetus Ocean, while the
Rheic Ocean expanded in the southern coast of Avalonia. The collision also resulted in the formation of the northern
Appalachians.
Siberia sat near Euramerica, with the
Khanty Ocean between the two continents. While all this was happening, Gondwana drifted slowly towards the South Pole. This was the first step of the formation of Pangaea.
The second step in the formation of Pangaea was the collision of Gondwana with
Euramerica. By
Silurian time, Baltica had already collided with Laurentia to form Euramerica.
Avalonia hadn't collided with
Laurentia yet, and a seaway between them, a remnant of the
Iapetus Ocean, was still shrinking as Avalonia slowly inched towards Laurentia.
Meanwhile,
southern Europe fragmented from Gondwana and started to head towards Euramerica across the newly formed
Rheic Ocean and collided with southern
Baltica in the
Devonian, though this microcontinent was an underwater plate. The Iapetus Ocean's sister ocean, the Khanty Ocean, was also shrinking as an island arc from Siberia collided with eastern Baltica (now part of Euramerica). Behind this
island arc was a new ocean, the
Ural Ocean.
By late Silurian time,
North and
South China rifted away from Gondwana and started to head northward across the shrinking Proto-Tethys Ocean, and on its southern end the new
Paleo-Tethys Ocean was opening. In the Devonian Period, Gondwana itself headed towards Euramerica, which caused the Rheic Ocean to shrink.
In the Early
Carboniferous, northwest
Africa had touched the southeastern coast of
Euramerica, creating the southern portion of the
Appalachian Mountains, and the
Meseta Mountains.
South America moved northward to southern Euramerica, while the eastern portion of Gondwana (
India,
Antarctica and
Australia) headed towards the South Pole from the
equator.
North China and South China were on independent continents. The
Kazakhstania microcontinent had collided with
Siberia (Siberia had been a separate continent for millions of years since the deformation of the supercontinent
Pannotia) in the Middle Carboniferous.
Western
Kazakhstania collided with
Baltica in the Late Carboniferous, closing the
Ural Ocean between them, and the western Proto-Tethys in them (
Uralian orogeny), causing the formation of the
Ural Mountains, and the formation of the supercontinent of Laurasia. This was the last step of the formation of Pangaea.
Meanwhile, South America had collided with southern
Laurentia, closing the
Rheic Ocean, and forming the southernmost part of the
Appalachians and
Ouachita Mountains. By this time, Gondwana was positioned near the South Pole, and glaciers were forming in Antarctica, India, Australia, southern Africa and South America. The
North China block collided with
Siberia by Late Carboniferous time, completely closing the Proto-Tethys Ocean.
By Early
Permian time, the
Cimmerian plate rifted away from Gondwana and headed towards Laurasia, with a new ocean forming in its southern end, the
Tethys Ocean, and the closure of the
Paleo-Tethys Ocean. Most of the landmasses were all in one. By the
Triassic Period, Pangaea rotated a little, in a southwest direction. The Cimmerian plate was still travelling across the shrinking Paleo-Tethys, until the
Middle Jurassic time. The Paleo-Tethys had closed from west to east, creating the
Cimmerian Orogeny. Pangaea looked like a
C, with an ocean inside the
C, the new Tethys Ocean. Pangaea had rifted by the Middle Jurassic, and its deformation is explained below.
Evidence of Pangaea's existence
Fossil evidence for Pangaea includes the presence of similar and identical species on continents that are now great distances apart. For example, fossils of the
therapsid Lystrosaurus have been found in Argentina, South Africa, India and Australia, alongside members of the
Glossopteris flora, whose distribution would have ranged from the polar circle to the equator if the continents would have been in their present position; similarly, the freshwater reptile
Mesosaurus has only been found in localized regions of the coasts of Brazil and West-Africa.
Additional evidence for Pangaea is found in the geology of adjacent continents, including matching geological trends between the eastern coast of South America and the western coast of Africa.
Rifting and break-up of Pangaea
There were three major phases in the break-up of Pangaea. The first phase began in the
Early-
Middle Jurassic, when Pangaea created a rift from the Tethys Ocean in the east and the
Pacific in the west. The rifting took place between North America and Africa, and produced multiple failed rifts. The rift resulted in a new ocean, the
Atlantic Ocean.
The Atlantic Ocean didn't open uniformly; rifting began in the north-central Atlantic. The
South Atlantic didn't open until the
Cretaceous. Laurasia started to rotate clockwise and moved northward with North America to the north, and
Eurasia to the south. The clockwise motion of Laurasia also led to the closing of the Tethys Ocean. Meanwhile, on the other side of Africa, new rifts were also forming along the adjacent margins of east Africa, Antarctica and
Madagascar that would lead to the formation of the southwestern
Indian Ocean that would also open up in the Cretaceous.
The second major phase in the break-up of Pangaea began in the
Early Cretaceous (150–140 Ma), when the minor supercontinent of Gondwana separated into four multiple continents (Africa, South America, India and Antarctica/Australia). About 200 Ma, the continent of
Cimmeria, as mentioned above (see "
Formation of Pangaea"), collided with Eurasia. However, a subduction zone was forming, as soon as Cimmeria collided.
This subduction zone was called the
Tethyan Trench. This trench might have subducted what is called the Tethyan
mid-ocean ridge, a ridge responsible for the Tethys Ocean's expansion. It probably caused Africa, India and Australia to move northward. In the Early Cretaceous,
Atlantica, today's South America and Africa, finally separated from eastern Gondwana (Antarctica, India and Australia), causing the opening of a "South Indian Ocean". In the Middle Cretaceous, Gondwana fragmented to open up the South Atlantic Ocean as South America started to move westward away from Africa. The South Atlantic didn't develop uniformly; rather, it rifted from south to north.
Also, at the same time,
Madagascar and India began to separate from Antarctica and moved northward, opening up the Indian Ocean. Madagascar and India separated from each other 100–90 Ma in the Late Cretaceous. India continued to move northward toward Eurasia at 15 centimeters (6 in) per year (a plate tectonic record), closing the Tethys Ocean, while Madagascar stopped and became locked to the
African Plate.
New Zealand,
New Caledonia and the rest of
Zealandia began to separate from Australia, moving eastward towards the
Pacific and opening the
Coral Sea and
Tasman Sea.
The third major and final phase of the break-up of Pangaea occurred in the early
Cenozoic (
Paleocene to
Oligocene). North America/
Greenland broke free from Eurasia, opening the
Norwegian Sea about 60–55 Ma. The Atlantic and Indian Oceans continued to expand, closing the Tethys Ocean.
Meanwhile, Australia split from Antarctica and moved rapidly northward, just as India did more than 40 million years earlier, and is currently on a collision course with
eastern Asia. Both Australia and India are currently moving in a northeastern direction at 5–6 centimeters (2–3 in) per year. Antarctica has been near or at the South Pole since the formation of Pangaea about 280 Ma. India started to collide with
Asia beginning about 35 Ma, forming the
Himalayan orogeny, and also finally closing the
Tethys Seaway; this collision continues today. The African Plate started to change directions, from west to northwest toward
Europe, and South America began to move in a northward direction, separating it from Antarctica and allowing complete oceanic circulation around Antarctica for the first time, causing a rapid cooling of the continent and allowing
glaciers to form. Other major events took place during the
Cenozoic, including the opening of the
Gulf of California, the uplift of the
Alps, and the opening of the
Sea of Japan. The break-up of Pangaea continues today in the
East Africa Rift; ongoing collisions may indicate the incipient creation of a new
supercontinent.
Further Information
Get more info on 'Pangaea'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://pangaea.totallyexplained.com">Pangaea Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
