About 300 million years in the past, Earth did not have seven continents, however as a substitute one large supercontinent referred to as Pangaea, which was surrounded by a single ocean referred to as Panthalassa.
The clarification for Pangaea’s formation ushered within the trendy principle of plate tectonics, which posits that the Earth’s outer shell is damaged up into a number of plates that slide over Earth’s rocky shell, the mantle.
Over the course of the planet’s 4.5 billion-year historical past, a number of supercontinents have shaped and damaged up, a results of churning and circulation within the Earth’s mantle, which makes up 84% of the planet’s quantity, according to the U.S. Geological Survey. This breakup and formation of supercontinents has dramatically altered the planet’s historical past.
“This is what’s driven the entire evolution of the planet through time. This is the major backbeat of the planet,” stated Brendan Murphy, a geology professor on the St. Francis Xavier University, in Antigonish, Nova Scotia.
Pangaea’s historical past
More than a century in the past, the scientist Alfred Wegener proposed the notion of an ancient supercontinent, which he named Pangaea (typically spelled Pangea), after placing collectively a number of strains of proof.
The first and most blatant was that the “continents fit together like a tongue and groove,” one thing that was fairly noticeable on any correct map, Murphy stated. Another telltale trace that Earth’s continents had been all one land mass comes from the geologic document. Coal deposits present in Pennsylvania have an analogous composition to these spanning throughout Poland, Great Britain and Germany from the identical time interval. That signifies that North America and Europe should have as soon as been a single landmass. And the orientation of magnetic minerals in geologic sediments reveals how Earth’s magnetic poles migrated over geologic time, Murphy stated.
In the fossil document, equivalent crops, such because the extinct seed fern Glossopteris, are discovered on now broadly disparate continents. And mountain chains that now lie on completely different continents, such because the Appalachians within the United States and the Atlas Mountains spanning Morocco, Algeria and Tunisia had been all a part of the Central Pangaea Mountains, shaped by means of the collision of the supercontinents Gondwana and Laurussia.
The phrase “Pangaea” comes from the Greek “pan,” which suggests “all,” and “gaia” or “Earth,” according to the Online Etymology Dictionary. The supercontinent shaped by means of a gradual course of spanning just a few hundred million years.
In the early Phanerozoic eon (541 million years in the past to now), nearly all the continents had been within the Southern Hemisphere, with Gondwana, the most important continent, spanning from the South Pole to the equator, in line with a chapter within the scientific guide “Ancient Supercontinents and the Paleogeography of Earth” (Elsevier, 2021). The Northern Hemisphere was largely lined by the Panthalassic Ocean. Another ocean — referred to as Iapetus, after a legendary Greek titan — between the paleo-continents Laurentia, Baltica and Gondwana, started to shut through the Ordovician interval (485 million to 444 million years in the past) after which disappeared through the Silurian interval (444 million to 419 million years in the past), when Baltica and Avalonia collided with Laurentia to type Laurussia, in line with the chapter, “Phanerozoic paleogeography and Pangea.”
Finally, about 320 million years in the past, there was a significant collision, geologically talking, “when Gondwana, Laurussia, and intervening terranes collided to form the Pangea supercontinent,” in line with the chapter, written by Earth scientists Trond Torsvik, Mathew Domeier and Robin Cocks.
However, Pangaea wasn’t the megalithe most individuals assume it’s. “Pangea never included all the continents at any one time,” in line with the chapter. For occasion, “the Paleotethys Ocean to the east of Pangea remained wide throughout the Carboniferous [359 million to 299 million years ago] and presented something of a barrier between the supercontinent and a number of large, independent Asian terranes, including Tarim, North China, South China, and Annamia.”
Later, through the Permian interval (299 million to 251 million years in the past), “many former peri-Gondwanan terranes drifted off the north-east Gondwana margin, commencing the opening of the Neotethys Ocean,” in line with the chapter.
When did Pangaea break aside?
Pangaea broke up in a number of phases between 195 million and 170 million years in the past. The breakup started about 195 million years in the past within the early Jurassic interval, when the Central Atlantic Ocean opened, in line with the chapter. The supercontinent fractured largely alongside earlier sutures.
Gondwana (what’s now Africa, South America, Antarctica, India and Australia) first cut up from Laurasia (Eurasia and North America). Then about 150 million years in the past, Gondwana broke up. India peeled off from Antarctica, and Africa and South America rifted, in line with a 1970 article within the Journal of Geophysical Research. Around 60 million years in the past, North America cut up off from Eurasia.
Pangaea’s local weather
Having one large landmass made for very completely different climatic cycles. For occasion, the inside of the continent might have been totally dry, because it was locked behind large mountain chains that blocked all moisture or rainfall, Murphy stated.
But the coal deposits discovered within the United States and Europe reveal that elements of the ancient supercontinent close to the equator should have been a lush, tropical rainforest, much like the Amazonian jungle, Murphy stated. (Coal kinds when lifeless crops and animals sink into swampy water, the place stress and water remodel the fabric into peat, then coal.)
“The coal deposits are essentially telling us that there was plentiful life on land,” Murphy instructed Live Science.
Climate fashions verify that the continental inside of Pangaea was extraordinarily seasonal, in line with a 2016 article within the journal Palaeogeography, Palaeoclimatology, Palaeoecology. The researchers on this examine used organic and bodily knowledge from the Moradi Formation, a area of layered paleosols (fossil soils) in northern Niger, to reconstruct the ecosystem and local weather through the time interval when Pangaea existed. Comparable with the modern-day African Namib Desert and the Lake Eyre Basin in Australia, the local weather was typically arid with brief, recurring moist intervals that sometimes included catastrophic flash floods.
The local weather additionally influenced the place animals lived. During the late Triassic, Reptile-like animals within the household Procolophonidae lived in a single area, whereas mammal family members, generally known as cynodonts, lived in one other, a 2011 examine within the journal Proceedings of the National Academy of Sciences discovered. Cynodonts inhabited one tropical space of Pangaea, the place monsoon-like rains fell twice a yr. Up north, procolophonids lived in temperate areas the place it solely rained yearly. It’s possible that the cynodonts wanted a water-rich space, which restricted their actions on Pangaea, the researchers stated.
“It’s interesting that something as basic as how the body deals with waste can restrict the movement of an entire group,” Whiteside said in a statement. In drier areas, “the reptiles had a competitive advantage over mammals,” which is probably going why they stayed there, Whiteside stated.
Pangaea existed for greater than 100 million years, and through that point many animal teams thrived. During the Permian interval, bugs corresponding to beetles and dragonflies flourished, as did the predecessors of mammals: the synapsids. But the existence of Pangaea overlapped with the worst mass extinction in historical past, the Permian-Triassic (P-TR) extinction occasion. Also referred to as the Great Dying, it occurred round 252 million years in the past and precipitated 96% of all marine species and round 70% of terrestrial species to go extinct, according to the Geological Society of America.
The early Triassic interval noticed the rise of archosaurs, a gaggle of animals that finally gave rise to crocodiles, birds and a plethora of reptiles, together with pterosaurs. And about 230 million years in the past a few of the earliest dinosaurs emerged on Pangaea, together with theropods, largely carnivorous dinosaurs that largely had air-filled bones and feathers much like birds.
Cycle in historical past
The present configuration of continents is unlikely to be the final. Supercontinents have shaped a number of instances in Earth’s historical past, solely to be cut up off into new continents. Right now as an illustration, Australia is inching towards Asia, and the japanese portion of Africa is slowly peeling off from the remainder of the continent.
Based on the emergence of different supercontinents within the Precambrian supereon (4.5 billion to 541 million years in the past), it seems that supercontinents happen periodically each 750 million years, in line with a 2012 examine within the journal Gondwana Research.
Most scientists consider that the supercontinent cycle is essentially pushed by circulation dynamics within the mantle, in line with a 2010 article within the Journal of Geodynamics.
Beyond that, the main points get fuzzy. While the warmth shaped within the mantle possible comes from the radioactive decay of unstable components, corresponding to uranium, scientists do not agree on whether or not there are mini-pockets of warmth move inside the mantle, or if your complete shell is one massive warmth conveyor belt, Murphy stated.
Current analysis on Pangaea
Scientists have created mathematical, 3D simulations to higher perceive the mechanisms behind continental motion. In a 2018 article within the journal Geoscience Frontiers, Earth scientists Masaki Yoshida and M. Santosh defined how they produced simulations of large-scale continental actions because the breakup of Pangaea about 200 million years in the past. The fashions present how tectonic plate movement and mantle convection forces labored collectively to interrupt aside and transfer giant land plenty. For instance, Pangaea’s giant mass insulated the mantle beneath, inflicting mantle flows that triggered the preliminary breakup of the supercontinent. Radioactive decay of the higher mantle additionally raised the temperature, inflicting upward mantle flows that broke off the Indian subcontinent and initiated its northern motion.
Yoshida and Santos created further geological fashions to foretell mantle convection and continental motion patterns 250 million years sooner or later. These fashions counsel that over thousands and thousands of years, the Pacific Ocean will shut as Australia, North America, Africa, and Eurasia come collectively within the Northern Hemisphere. Eventually, these continents will merge, forming a supercontinent referred to as “Amasia.” The two remaining continents, Antarctica and South America, are predicted to stay comparatively motionless and separate from the brand new supercontinent.
Additional reporting by Carol Stoll, Live Science contributor
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