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Feb 10th, 2012 12:37 AM #1
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- Feb 2010
How Earth's Next Supercontinent Will Form comentary thread
The Earth has been covered by giant combinations of continents, called supercontinents, many times in its past, and it will be again one day in the distant future. The next predicted supercontinent, dubbed Amasia, may form when the Americas and Asia both drift northward to merge, closing off the Arctic Ocean, researchers suggest.
Supercontinents are giant landmasses made up of more than one continental core. The best-known supercontinent, Pangaea, was once the world's only continent — it was on it that the dinosaurs arose — and was the progenitor of today's continents.
Conventional models of how supercontinents evolve suggest they form on top of the previous supercontinent, known as introversion, or on the opposite side of the world from that supercontinent, known as extroversion. Under these models Amasia would therefore either form where Pangaea once was, with the Americas meeting with Asia to close off the Atlantic Ocean, or form on the other side of the planet from where Pangaea was, with the Americas merging with Asia to close off the Pacific Ocean.
Now, geologists suggest that Amasia might emerge sideways from where Pangaea once existed, in what is now the Arctic, a process known as orthoversion. Moreover, this new model seems consistent with models of how past supercontinents formed, said researcher Ross Mitchell, a geologist at Yale University.
Which way did it form?
The introversion model, on the one hand, assumes that the oceanic plate between continents that formed when a supercontinent pulled apart has stopped spreading. As such, there is nothing to keep the continents from drifting back together and forming another supercontinent. The extroversion model, on the other hand, proposes that the oceanic plate that formed when a supercontinent pulled apart would keep spreading. The continents then drift away from it, meeting up on the other side of the planet to merge.
The new orthoversion model from Mitchell and his colleagues bases its motion of continents on where the edges of past supercontinents were. For instance, when Pangaea broke up, its rim dove or subducted downward into the earth. This subduction zone, which encircles the Pacific Ocean, is known as the Ring of Fire, and is where many of the largest earthquakes and volcanic eruptions now take place.
The orthoversion model proposes that the subduction zone surrounding a one-time supercontinent drives where its former components end up going. This suggests that modern continents will slide either north or south around the Ring of Fire. Since the Caribbean Sea between North and South America and the Arctic Ocean between the Americas and Asia appear transient in nature, the researchers suggest the Americas and Asia will go north instead of south, meeting at the Arctic to form Amasia.
To see which model of the supercontinent cycle might be right, the researchers tried to see which best matched data on how past supercontinents formed. These included Pangaea, as well as Rodinia, which existed between 750 million and 1.1 billion years ago, and Nuna, which existed between 1.5 billion to 1.8 billion years ago.
To see how the components of supercontinents moved, scientists analyzed the impact that Earth's magnetic field has on ancient rocks. Magnetic minerals in molten rock can act like compasses, aligning with the planet's magnetic field lines, an orientation that gets frozen in place once the rock solidifies. Since these lines generally run north-south, looking at the way these minerals point can shed light on how the landmasses they are a part of might have drifted in space over time.
The researchers found that Pangaea apparently formed at nearly a 90-degree angle from the direction along which Rodinia fragmented — that is, Pangaea formed neither where Rodinia once was nor on the opposite side of the planet, but somewhere nearly exactly between those spots. Rodinia seemingly emerged in a similar manner from Nuna. Both findings support orthoversion as the explanation for how supercontinents form and fragment.
"Now that we have a clear picture of what the supercontinent cycle actually looks like, we can begin to answer the questions of why the supercontinent cycle operates as it does," Mitchell told OurAmazingPlanet. "Why a supercontinent breaks apart remains an unanswered question."
When to expect Amasia
These findings could also help scientists better understand the history of life on this planet, by figuring out where landmasses were and how organisms might have dispersed.
"Continents with similar fossil records likely share an evolutionary ancestry, but actually establishing a land bridge by juxtaposing those continents is finding the smoking gun," Mitchell said.
As to when Amasia might form, that is "difficult to answer, because the supercontinent cycle is not as regular as the seasonal cycle, for example," Mitchell said. "But we can get a clue from Earth's history — the cycle is speeding up, such that the recurrence interval between successive supercontinents has become less and less. Knowing that Pangea formed 300 million years ago, we can predict a range of Amasia ages from 50 to 200 million years from now."
The scientists detailed their findings in the Feb. 9 issue of the journal Nature.Jim Crow America relegated Blacks to the back of buses. Israel wants Arabs excluded from the bus entirely.
Feb 10th, 2012 12:39 AM #2
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- Feb 2010
I doubt their will ever be another super continent. Rather I suspect our larger continents will continue to break apart into smaller and smaller chunks ... but thats eons away.Jim Crow America relegated Blacks to the back of buses. Israel wants Arabs excluded from the bus entirely.
Feb 15th, 2012 9:34 AM #3
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- Feb 2011
- next to a volcano near a subduction zone fault line by the ocean.
I was always under the impression that the American continent was moving southwest in response to the asian plate moving northwest, like 2 gears turning each other around."Jake 99 is Lord!"
Feb 15th, 2012 10:22 AM #4
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- Oct 2006
- 64th latitude north....Where global warming is a plus
Nice post Anarch
What allows movement away from the spreading ridges is the opposite end having a well functioning subduction zone. With the north American plate moving in a predominate westward direction from the mid Atlantic ridge, ( roughly 3cm a year) it meets a resistance along the strike fault between San Francisco and L.A. at the Pacific plate margin. This has forced the pacific plate to travel northwards in attempt to get around the blockage, splitting Baja California away from Mexico in the process, and forcing the North American plate to jam up at the strike zone. But further north you have the cascadia subduction zone allowing the Pacific plate to slide under and remelt through inland volcanism.
What may appear in 100 million years would be the Baja peninsula and the western side of California at the L.A fault zone ending up around San Fransisco, some 400 miles north. But obviously this is speculative based on the current directions the plates are now taking, if the jamming effect is somehow broken at depth, this would change the directions dramatically, perhaps extending the cascadia volcanism further south.
There are so many variables to consider, like the Rio Grande rift system, or New Madrid, both of which have been the result of a predominately westward movement and failed rifting. ( the attempt at continental breakup)
when again touched, as surely they will be, by the better angels of our nature
Feb 15th, 2012 10:44 AM #5
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- Feb 2010
Tis not my post but MMs news article... I just made this second thread so we could discuss the news article.Jim Crow America relegated Blacks to the back of buses. Israel wants Arabs excluded from the bus entirely.
Feb 16th, 2012 12:33 AM #6
The information regarding some recent findings of a specific mite was interesting. Not sure if that was included in the article mentioned. However, it led to a realization that Florida was part of west Africa when the rest of our major land mass was from somewhere else. Have you seen the Nat Geo video on this topic?
Feb 19th, 2012 12:13 AM #7
Paleo-stuff is cool. I got a few sites that have animated maps showing plate tectonic movements. Those are from the Paleomap Project.This White House photograph is made available for publication by news organizations or personal use printing by the subject(s) of the photograph. The photograph may not be manipulated in any way and may not be used in commercial or political materials, advertisements, emails, products, promotions that suggests approval or endorsement of the President, the First Family, or the White House.
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