Mega Pacific Ocean

The Mega Pacific Ocean is the Superocean that will surround the future Supercontinent Pangaea Ultima. There are two scenarios to assembling the present continents into a new future Supercontinent.

The first scenario is the complete closure of the present Pacific Ocean caused by a collision of east Asia withAustralia and America. The resulting supercontinent is called Amasia (from America and Asia). This Scenario is assumed by Roy Livermore, now at the University of Cambridge, in the late 1990s. The Atlantic Ocean will became the new Superocean Super Atlantic Ocean with a fast spreading Mid Ocean Ridge like in the present Pacific Ocean and surrounded by Subduction Zones like the Panthalassic Ocean 250 million years ago.

This second scenario is assumed by Christopher Scotese and leads to the formation of Pangaea Ultima. In this scenario, the Pacific Ocean will still be closing the next 50 million years like The INDIAN Ocean and the Atlantic Ocean will be widening. But in the northern Indian Ocean, south of India and west of Australia, new Subduction Zones will be emerging as well as a new Subduction Zones in the western Atlantic Ocean. This results in a widening of the Pacific Ocean, the closing of the Atlantic and Indian Oceans and the formation of Pangaea Ultima. The present Pacific Ocean will become a Superocean - the Mega Pacific Ocean.

Formation

Present Situation

The present Situation in the Pacific Ocean is a shrinking major Ocean with the East Pacific Rise, which is partially subducted beneath North America. This Pacific Ocean is surrounded by large Subduction Zones. In the north and east, the pacific plate is subducted beneath the North American Plate and South American Plate. In the west and south west, the pacific plate is subducted beneath the Australian Plate and the Filipino Plate. The Subduction Zones in the east are convergent Continent Ocean BOUNDARIES with deep trenches on the Ocean side and high volcanic mountain Ranges on the Continent side (overriding plate).

The Subduction Zones in the north and west are convergent Ocean Ocean boundaries with a deep trench of the pacific plate side and volcanic Island arcs on the overriding plate side. But in the western Pacific, the tectonic structure of the subduction Zones is more complex than at the convergent Continent Ocean boundary in the eastern Pacific. Because in the western pacific is very old oceanic crust which is 60 to 150 million years old. This old oceanic crust in the western Pacific has a heavier weight than the young oceanic crust in the eastern Pacific. This leads to a greater slap pull and a steeper subduction angle of the subducted crust. The steeper subduction angle and the greater slap pull of the old oceanic crust at the western part of the pacific plate results in extensional stress in the overriding plate and the formation of backarc rift systems and backarc spreading centers which split the volcanic arcs into two parts. The direction of the backarc rift zone and spreading center are often parallel to the direction of the trenches. Backarc rift zones and spreading centers can only develop in the rheologic weaker oceanic crust in the magmatic (volcanic) islands arcs because the oceanic crust is too rigid to break up like continental crust (east Africa, Breakup of Pangaea). The rheologic weaker oceanic crust in magmatic island arcs is more brittle than normal rigid oceanic crust, compressional faults can turn to extensional faults if extensional stress rising in the overriding plate with the magmatic island arc and this will caused in the splitting of the magmatic island arc by the rift zones and spreading centers.

Present candidates for ACTIVE backarc rifting and spreading in the western pacific:

  • Okinawa Arc (rift system)
  • Izu-Bonin-Mariana Arc (rift systems and spreading center)
  • Ayu Trough (spreading center)
  • Woodlark Basin (spreading center)
  • Bismarck sea (spreading center)
  • North Fiji Basin (spreading center)
  • Tonga Arc and Lau Basin (spreading center)
  • Kermadec Arc and Havre Trough (rift system)

Future Development of Mid Ocean Ridge Systems in the Pacific Ocean

The above-named backarc rift systems and spreading centers might play a important role to development of new Mid Ocean ridge Systems in the Pacific ocean. The maps of the future earth from Christopher Scotese shows that the Pacific ocean will shrinking the next 50 million years. But in times more far than 50 million years, the maps of Christopher Scotese shows a new Mid Ocean Ridge in the western Pacific, connecting to the arctic Ridge System. But Christopher Scotese no show how in the Pacific Ocean a new Mid Ocean Ridge System will emerge.

If the Pacific Ocean keeps shrinking the next 50 million years, the present spreading ridge of this ocean will completely subduct benath North and South America. Only a "small" amount will remain of the former East Pacific Rise, the Pacific Antarctic Ridge will survive in the south Pacific Ocean and connect with the Southeast Indian Ridge. But this remains are too short to form a Mid Ocean Ridge System in a widening ocean. In the normal ocean crust in the western Pacific Ocean no new rift systems or spreading centers can emerge because normal oceanic crust is too rigid to break up.

In the model proposed byChristopher Scotese for the earth in 150 million years, he shows that the eastern part of Siberia will break up and became a part of northwestern North America. But this is only a short part of the new Mid Ocean Ridge which will develop, if the assumption of Christopher Scotese correct. But how in the western Pacific Ocean a new Mid Ocean Ridge System can develop?

Christopher Scotese has no answer of these Question. There are no Continental fragments at the western edge of pacific those can rift apart from east Asia to form a new Mid Ocean Ridge System in western Pacific. Only East Sibiria will break up from Asia and moving to North America. If there a Mid Ocean Ridge in the Ocean, the Ocean can widening both sides of the Ridge, but new spreading centers cannot emerge from the break up of normal oceanic crust (its too rigid).

New Rift Systems can only develop in brittle continental crust. This crust is thinning by extensional stress and/or heating by hot spots resulting in a break up of the continental crust and formation of rift systems (East Africa, Pangaea). These continental rift systems can widening by further extensional stress and became active spreading centers (like in Ethiopia and the Red Sea). The only parts of crusts in western pacific there are more brittle than the normal rigid oceanic crust are the rheologic weaker parts of oceanic crusts in the volcanic island arcs. The backarc rift systems and spreading centers in the western Pacific are good candidates to form a new Mid Ocean Ridge System in the western Pacific Ocean.

The break up of volcanic island arc in western Pacific might cause widening of the Pacific Ocean in future geological times (50 to 100 million years in the future) and develop a new Mid Ocean Ridge in the western Pacific Ocean. The new western Pacific Ridge System will propagate into the continental crust of the Eurasian Plate. This caused in rifting and break up of the eastern Part of Sibiria and will connect the western Pacific Ridge System with the Ridge System in the Arctic Ocean. The Arctic Ocean became a part of the Mega Pacific Ocean, while the Atlantic Ocean will closing.

The new Superocean

Subduction Zones

If the Atlantic Ocean will completely closing and the Indian Ocean will became a great lake (like the Present CASPIAN Sea), the Pacific Ocean became a Superocean - the Mega Pacific Ocean.

This Ocean will surrounded by subduction Zones. In these Subduction Zones the older Oceanic crust of the Mega Pacific Ocean will subducted benath the Supercontinent Pangaea Ultima. It will be a similar Situation in 250 million years in the future like 250 million years ago with the Supercontinent Pangaea and the Superocean Panthalassic Ocean.

Mid Ocean Ridge Systems

The estimation of the Position of the Mid Ocean Ridge Systems in the Mega Pacific Ocean are more complicated than the estimation of the Position of the Subduction Zones. Because the Subduction Zones are located at the Continent Ocean Boundary. The Mid Ocean Ridge System in the western Pacific might moved by slap pull and incrasing spreading rates in the middle of the new Superocean.

But an exactly estimation is no possible, because geolocig plate motions in the future can only assumed but not predicted exactly.

See also

  • Panthalassic Ocean
  • Super Atlantic Ocean
  • Pan-African Ocean
  • Mirovia
  • Pacific Ocean
  • Back-arc basin
  • Paleomap

Top Reference

Taylor, B., Martinez, F., Back-arc basin basalt systematics, Earth and Planetary Science Letters, 210, 2003, 481-497.

References

Nishimura, S., Why are there no back-arc basins around the eastern Pacific margin? Revista Mexicana de Ciencias Geológicas, v. 19, núm. 3, 2002, p. 17 0-174
Hawkins, J.W., Petrologic synthesis: Lau Basin transect (Leg 135), Proc. ODP, Sci. Res., 135, 879-905, 1994.
Parson, L.M. and J.W. Hawkins, Two stage ridge propagation and the geological history of the Lau backarc basin, Proc. ODP, Sci. Res., 135, 819-828, 1994.