A rough approximation of Pangaea Proxima according to the early model on the Paleomap Project website

Pangaea Proxima (also called Pangaea Ultima, Neopangaea, and Pangaea II) is a possible future supercontinent configuration. Consistent with the supercontinent cycle, Pangaea Proxima could form within the next 250 million years. This potential configuration, hypothesized by Christopher Scotese in November 1982, earned its name from its similarity to the previous Pangaea supercontinent. Scotese later changed Pangaea Ultima (Last Pangaea) to Pangaea Proxima (Next Pangaea) to alleviate confusion about the name Pangaea Ultima which could imply that it would be the last supercontinent.[1] The concept was suggested by extrapolating past cycles of formation and breakup of supercontinents, not on theoretical understanding of the mechanisms of tectonic change, which are too imprecise to make predictions that far into the future. "It's all pretty much fantasy to start with," Scotese has said. "But it's a fun exercise to think about what might happen. And you can only do it if you have a really clear idea of why things happen in the first place."[2]

Supercontinents describe the merger of all, or nearly all, of Earth's landmass into a single contiguous continent. In the Pangaea Proxima scenario, subduction at the western Atlantic, east of the Americas, leads to the subduction of the Atlantic mid-ocean ridge followed by subduction destroying the Atlantic and Indian basin, causing the Atlantic and Indian Oceans to close, bringing the Americas back together with Africa and Europe. As with most supercontinents, the interior areas of Pangaea Proxima are presumed to become humid, semi-arid deserts that will be prone to extreme temperatures up to 55°C.[3] Most land mammals; including humans are speculated to be driven to extinction because of these environments; albeit there is no consensus.[4]

Formation

According to the Pangaea Proxima hypothesis, the Atlantic and Indian Oceans will continue to get wider until new subduction zones bring the continents back together, forming a future Pangaea. Most continents and microcontinents are predicted to collide with Eurasia, just as they did when most continents collided with Laurentia.[5]

In the next 50 million years (assuming no new subduction zones come into being before then), North America is predicted to shift west and Eurasia east, and possibly even to the south, bringing Great Britain closer to the North Pole and Siberia southward towards warm, subtropical latitudes. Africa is predicted to collide with Europe and Arabia, closing the Mediterranean Sea (thus completely closing the Tethys Ocean (or Neotethys)) and the Red Sea. A long mountain range (the Mediterranean Mountain Range) would then extend from Iberia, across Southern Europe and into Asia. Some are even predicted to have peaks higher than Mount Everest. Similarly, Australia is predicted to beach itself past the doorstep of Southeast Asia, causing the islands to be compressed inland, forming another potential mountain range. Meanwhile, Southern and Baja California are predicted to have already collided with Alaska with new mountain ranges formed between them.[6]

About 125 million years from now, the Atlantic Ocean is predicted to stop widening and begin to shrink as the Mid-Atlantic Ridge seafloor spreading gives way to subduction. In this scenario, the mid-ocean ridge between South America and Africa will probably be subducted first; the Atlantic Ocean is predicted to narrow as a result of subduction beneath the Americas. The Indian Ocean is also predicted to be smaller due to northward subduction of oceanic crust into the Central Indian trench. Antarctica is expected to split in two and shift northwards, colliding with Madagascar and Australia, enclosing a remnant of the Indian Ocean, which Scotese calls the "Medi-Pangaean Sea".[7][8]

When the last of the Mid-Atlantic Ridge is subducted beneath the Americas, the Atlantic Ocean is predicted to close rapidly.[9]

At 250 million years in the future, the Atlantic is predicted to have closed, with only small vestiges of the former ocean remaining. North America will have collided with Africa, but be in a more southerly position than where it rifted away. South America is predicted to be wrapped around the southern tip of Africa and Antarctica, completely enclosing the Medi-Pangaean Sea, which will become a supertoxic inland sea that begins to poison the surrounding oceans, lands and atmosphere, leading to another great extinction event.[7] The supercontinent will be encircled by a global ocean, the Neopanthalassan Ocean (meaning "new" Panthalassan Ocean),[7] which encircles half the Earth.[9] The Earth is expected to have a hothouse climate with an average global temperature of 28 °C (82 °F).[7]

Breakup and solidification of the outer core

The formation of Pangaea Proxima will probably dramatically affect the environment. The collision of plates will result in mountain building, thereby shifting weather patterns. The sea level may drop because of increased glaciation. The rate of surface weathering may rise, increasing the rate at which organic material is buried. Pangaea Proxima also has the potential to lower global temperatures and an increase in atmospheric oxygen. This, in turn, can affect the climate, further lowering global temperatures.[10] These changes as described above can result in more rapid biological evolution as new niches emerge.

Pangaea Proxima could also insulate the mantle. The flow of heat will be concentrated, resulting in volcanism and the flooding of large areas with basalt. Rifts will form and Pangaea Proxima will split up once more in 400 to 500 million years. Earth may thereafter experience a warming period as occurred during the Cretaceous period, which marked the split-up of the previous Pangaea supercontinent.[11] It will probably form a new Atlantic Ocean, but nobody knows for sure what the map of the world looks like when Pangaea Proxima breaks up. After the break-up the continents may form a new supercontinent again in 600 to 700 million years by which time total solar eclipses will be impossible due to the moon moving away from Earth.

The iron-rich core region of the Earth is divided into a 2,440 km (1,520 mi) diameter solid inner core and a 6,960 km (4,320 mi) diameter liquid outer core.[12] The rotation of the Earth creates convective eddies in the outer core region that cause it to function as a dynamo. This generates a magnetosphere about the Earth that deflects particles from the solar wind, which prevents significant erosion of the atmosphere from sputtering. As heat from the core is transferred outward toward the mantle, the net trend is for the inner boundary of the liquid outer core region to freeze, thereby releasing thermal energy and causing the solid inner core to grow.[13] This iron crystallization process has been ongoing for about a billion years. In the modern era, the radius of the inner core is expanding at an average rate of roughly 0.5 mm (0.02 in) per year, at the expense of the outer core.[14] Nearly all of the energy needed to power the dynamo is being supplied by this process of inner core formation.[15]

The inner core is expected to consume most or all of the outer core 3–4 billion years from now, resulting in an almost completely solidified core composed of iron and other heavy elements. The surviving liquid envelope will mainly consist of lighter elements that will undergo less mixing. Alternatively, if at some point plate tectonics cease, the interior will cool less efficiently, which would slow down or even stop the inner core's growth. In either case, this can result in the loss of the magnetic dynamo. Without a functioning dynamo, the magnetic field of the Earth will decay in a geologically short time period of roughly 10,000 years. The loss of the magnetosphere will cause an increase in erosion of light elements, particularly hydrogen, from the Earth's outer atmosphere into space, resulting in less favorable conditions for life.[16]

Models

There are two models for the formation of Pangaea Proxima — an early model and the current model. The two models differ in where they place Australia, Antarctica and Chukotka.

The early model, created in 1982 and shown on the Paleomap Project website, places Australia and Antarctica connected to each other as a separate landmass to Pangaea Proxima, close to the South Pole, and Chukotka staying with Eurasia.

The current model, created in 2001 and shown on Christopher Scotese's YouTube channel,[17] has Australia attached to China, East Antarctica attached to South America, and West Antarctica attached to Australia, with Chukotka attached to North America (it is on the North American plate).

Other suggested supercontinents

Paleogeologist Ronald Blakey has described predictions of the next 15 to 85 million years of tectonic development as fairly settled, without supercontinent formation.[18] Beyond that, he cautions that the geologic record is full of unexpected shifts in tectonic activity driven by currents deep in the Earth's mantle which are largely undetectable and poorly understood, making longer projections "very, very speculative".[18] In addition to Pangaea Proxima, two other hypothetical supercontinents—"Amasia" and "Novopangaea"—were illustrated in an October 2007 New Scientist article.[19] Another supercontinent, Aurica, has been suggested in more recent times.

New research from Curtin University in Australia and Peking University in China supports an Amasia scenario within 200 to 300 million years. The study in the National Science Review suggests that the Pacific Ocean, shrinking since the time of the dinosaurs, may continue until it has closed entirely, resulting in the collision of the Americas with Eurasia.

See also

  • The Future Is Wild, television series which explores future evolution, including on Pangaea Proxima

References

  1. ↑ Williams, Caroline; Nield, Ted (October 2007). "Earth's next supercontinent". New Scientist. 196 (2626): 36–40. doi:10.1016/S0262-4079(07)62661-X.
  2. ↑ "Continents in collision: Pangaea Ultima". NASA Science News. 6 October 2000. Retrieved 1 October 2023.
  3. ↑ Kargel, Jeffrey S. (2004). "New World". Mars: a warmer, wetter planet. Springer. ISBN 978-1-85233-568-7.
  4. ↑ Farnsworth, Alexander; Lo, Y. T. Eunice; Valdes, Paul J.; Buzan, Jonathan R.; Mills, Benjamin J. W.; Merdith, Andrew S.; Scotese, Christopher R.; Wakeford, Hannah R. (October 2023). "Climate extremes likely to drive land mammal extinction during next supercontinent assembly". Nature Geoscience. 16 (10): 901–908. doi:10.1038/s41561-023-01259-3.
  5. ↑ Broad, William J. (9 January 2007). "Long-Term Global Forecast? Fewer Continents". The New York Times.
  6. ↑ "Our globe in next 50 million years". Volcano World. Oregon State University. Archived from the original on 5 April 2009.
  7. 1 2 3 4 Scotese, Christopher R. (30 May 2021). "An Atlas of Phanerozoic Paleogeographic Maps: The Seas Come In and the Seas Go Out". Annual Review of Earth and Planetary Sciences. 49 (1): 679–728. Bibcode:2021AREPS..49..679S. doi:10.1146/annurev-earth-081320-064052. S2CID 233708826.
  8. ↑ Scotese, Christopher R (2 February 2003). "The Atlantic Ocean begins to Close". Paleomap Project. Retrieved 24 March 2012.
  9. 1 2 Scotese, Christopher R (2 February 2003). "'Pangea Ultima' will form 250 million years in the Future". Paleomap Project. Retrieved 13 March 2006.
  10. ↑ Young, Grant M. (1 May 2013). "Precambrian supercontinents, glaciations, atmospheric oxygenation, metazoan evolution and an impact that may have changed the second half of Earth history". Geoscience Frontiers. 4 (3): 247–261. Bibcode:2013GeoFr...4..247Y. doi:10.1016/j.gsf.2012.07.003.
  11. ↑ Nance, R. Damian (September 2022). "The supercontinent cycle and Earth's long‐term climate". Annals of the New York Academy of Sciences. 1515 (1): 33–49. doi:10.1111/nyas.14849. PMC 9796656. PMID 35762733.
  12. ↑ http://eprints.whiterose.ac.uk/437/1/gubbinsd12.pdf
  13. ↑ Gubbins, David; Sreenivasan, Binod; Mound, Jon; Rost, Sebastian (1 May 2011). "Melting of the Earth's inner core". Nature. 473: 361–363. doi:10.1038/nature10068 – via NASA ADS.
  14. ↑ Monnereau, Marc; Calvet, Marie; Margerin, Ludovic; Souriau, Annie (1 May 2010). "Lopsided Growth of Earth's Inner Core". Science. 328: 1014. doi:10.1126/science.1186212 – via NASA ADS.
  15. ↑ Stacey, Frank D.; Stacey, Conrad H. B. (1 January 1999). "Gravitational energy of core evolution: implications for thermal history and geodynamo power". Physics of the Earth and Planetary Interiors. 110: 83–93. doi:10.1016/S0031-9201(98)00141-1 – via NASA ADS.
  16. ↑ van Thienen, P.; Benzerara, K.; Breuer, D.; Gillmann, C.; Labrosse, S.; Lognonné, P.; Spohn, T. (1 March 2007). "Water, Life, and Planetary Geodynamical Evolution". Space Science Reviews. 129: 167–203. doi:10.1007/s11214-007-9149-7 – via NASA ADS.
  17. ↑ Scotese, Christopher (18 September 2014). Future Plate Motions & Pangea Proxima - Scotese Animation. YouTube. Archived from the original on 21 December 2021. Retrieved 3 October 2020.
  18. 1 2 Manaugh, Geoff; Twilley, Nicola (23 September 2013). "What Did the Continents Look Like Millions of Years Ago?". The Atlantic. Retrieved 22 July 2014.
  19. ↑ Williams, Caroline; Nield, Ted (17 October 2007). "Pangaea, the comeback". New Scientist.

Further reading

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.