My science/technology-related thoughts, sometimes controversial, sometimes can be based on limited knowledge base, logic can be non-perfect as well. I develop my vision in iterations. Don't take this blog as an attempt to convince anybody in anything.
Each post in this blog reflects my level of understanding of Tectonics of the Earth at the time the post was written; so, some posts may not necessarily be correct now.

02 May, 2011

Continental Formation And Evolution.

If the concept of magma propagation in crust along temperature gradient caused by crust deformation is correct, then interesting perspective on Continental Formation is opening. Let's assume border forces are the main forces that drive continents. Then the next basic rules could be derived:
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- The main source of the force to move continents are ocean floor divergent boundaries.


- The main source of the force to break a continent apart are the divergent boundaries within the continent. These divergent boundaries later can start ocean floor spreading.

- The force a sub-ducting ocean floor is acting on the continent with, is much less than the force of non-sub-ducting floor. Therefore, the sum of vectors of forces acting on a continent would point the continent in the direction of its borders under which ocean floor sub-ducts.
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Let's go further:
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- If between two convergent boundaries one has to sub-duct, the more dense one would go down.


- The crust is made of the material that a) is lighter than underlying magma and b) have higher melting temperature than the temperature of the underlying magma.

- The sub-ducting crust may not necessarily melt under the continent, as current temperature of magma can be lower than the temperature of magma the old crust was formed at.
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The above rules lead us to a non-that-obvious mechanism of ocean floor / continent transformations:

1. Initial sequence: 
  - Very thin chunks of crust start to pop up all over the surface.
 

  - The chunks are drifted towards Earth poles by the Moon induced tidal waves.
 

  - All the surface is filled up with the chunks. Polar layers are thicker.
 

  - The chunks are merged into crust. Moon induced waves are braking the crust into big plates. The plates are getting thick enough to resist moon induced waves to overlap them. The underlying heat is blocked. Atmosphere and ocean are developing. Polar crust regions are the first continents as they are thicker and are made of lighter crust.

2. The ocean plates with the help of Moon develop divergent boundaries. The divergent boundaries stress the crust globally, the most stressed direction is East-West on Equator. The beginning of sub-ducting process is inevitable.

3. The weakest point breaks (probably with the help of some asteroid). If not with the help of the asteroid, it would probably break on Equator, as Equator crust at this time is newest, thinnest, and most stressed.

4. The sub-ducted crust around the fault line creates a continent. The crust sub-ducting under the continent borders expands the continent.  The distant divergent boundaries push the crust to the continent. The crust is getting jammed on its way toward the continent. The structure of the resulting islands I'd expect to be heavily twisted. The island are bumped into the continent's plate adding to the plate's area.

5. The two old Polar continents are moving toward the new continent, but not too fast as the diverging in North-South direction is slower than in East-West direction on Equator. Soon they enter the continent's Ring Of Fire of sub-ducting process and bump into the continent's plate, having traveled not too far. The remnants of those Polar continent's, I'd like to think, can be found in Australia and North of Canada and Greenland.

6. The line of Ring Of Fire of sub-ducting process expands to embrace the hemisphere the continent belongs to. Then The Ring Of Fire shrinks and disappears within the other hemisphere. Now again Earth's crust has no place to easily sub-duct the extra area added by newly developed crust. The divergent boundaries stress the crust. The beginning of new sub-ducting process is inevitable. Loop to paragraph 3.

7. A number of cycles of the process had passed, I'd like to think, before Earth's crust reached its current state.
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reposted from
http://sukhotinsky.blogspot.com/
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