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.

05 October, 2011

Hawaii Convergent, Part 2. Introducing The Concept Of Geofracture (not Plate) Tectonics.

Revisiting part one. 
   In my previous post: "Hawaii Hotspot Puzzle. Suggesting Hawaii As A Moving Convergent 'Coldspot'". < http://divergent-boundaries.blogspot.com/2011/09/hawaii-hotspot-puzzle-suggesting-hawaii.html > I tried to explain Hawaii seamount chain using the idea developed in my previous posts (and expressed in my message #6247 (24 Aug 2011 12:35) "A message on Active Boundary Plate Tectonics" to <GEO-TECTONICS@JISCMAIL.AC.UK> ) that:
a) the process of pumping magma/lava up requires:
- thermal gradient;
- deformations to cause sufficient local displacements of magma/lava;
b)
- if cooling of the upper layers of the boundary is "good enough" the boundary overcomes the compression in crust; a divergent process develops under Moon/Sun induced deformations;
 - if cooling of the upper layers of the boundary is not "good enough" the boundary can't overcome the compression in crust; a convergent process develops under Moon/Sun induced deformations;

   The post was focused on explaining Hawaii's "as a convergent 'Coldspot'":
- The geometry of global tectonic forces maintains focused deformations. Convergent process along a segment of line is developed under the external compression.
- The process of pumping magma/lava up surface stops when the segment gets out of focus of the deformations and the convergent location gets too thick and "diffused" in terms of thermal gradient. (Actually the phrase was without "on surface", it was just "the process of pumping magma/lava up", - my mistake).

The tail of the convergent "coldspot" does not break on fracture zones.
   In the post I tried to explain "Hawaii/Murray Fracture Zones" puzzle, - the microplates on both sides of Murray Fracture Zones were spread at different rates. After the Hawaii "head" passed Murray Fracture Zone, the path-line should be broken at the fracture zone, but it does not. The same holds for other fracture zones. The explanation (revisited) could be as follows:

How do different spreading rates of microplates get accommodated:
   When the process of pumping magma/lava to surface stops, does it mean that the deformations-induced convection stops beneath the ocean floor? I think, no, it does not due to the presence of thermal gradient and local displacements. Still, the sediments contaminated stuff circulates beneath a non-active volcano. The stuff just does not reach the surface. Now the wide region beneath the volcano gets spoiled with sediments, melting temperature drops, the effective thickness of crust drops as well. The volcano keeps on subsiding. The microplates different spreading rates get accommodated by, so to say, different rates of sea mount subsiding.

Even if a microplate spread faster, it can't shift a volcano segment far from the centerline.
   The most deformations are focused on the centerline; if a volcano segment is moved by the microplate off the centerline, the side of a volcano that is closer to the centerline is getting more amplitude of deformations, and the crust of the side is consumed more intensely, that's the kind of negative feedback to keep the volcano segments close and parallel to the centerline, but not too close to the centerline if the center is already occupied by other volcano segment because the crust there is contaminated with sediments. In that case of partially overlapped segments, I'd expect the head of a forward segment to be on the centerline, but it's rear to be off the center as the center is already occupied.
The "ductile" island chain as a part of a bigger picture.
  
   At some point the balance is reached, and the volcano subsidence stops. The balance is between volcano weight, crust effective thickness, compression stress in crust. (Roughly, the rate of change of effective thickness of crust depends on heat supply by the deformation induced convection, heat taken off through the surface and other factors). Such "ductile", so to say, island could probably be used to measure time variations of stress in oceanic crust. Perhaps a laser-based tools could do the job by measuring the island 3-D dimensions.

Geofracture (not Plate) Tectonics, talking on the concept of the interdisciplinary study.
   Number of branches of science can study Earths brittle/dactile layers, to name a few: Fracture mechanics, Continuum mechanics, Rheology. For example: 

- The pattern of global fracture zones (boundaries) in Earth's brittle layer developed due to Moon/Sun induced deformations could be handled by Fracture mechanics. Good example, I think, can be suggested mechanism behind The Siberian Traps. See my blog post "Ural-Putorana Diverged, Suggesting The Global Mechanism Behind The Event." < http://divergent-boundaries.blogspot.com/2011/08/ural-putorana-diverged-suggesting.html > The extension process of the region was suggested to happen due to forced move from higher latitudes to lower latitudes. Between the fixed boundaries such move from higher latitudes to lower means extension over the region.

- The property of a boundary to develop divergent or convergent process could be handled by Rheology, for instance the convergent property of Hawaii volcanoes chain (this and previous posts). The pattern of oceanic intra-plate convergent zones, still, can be handled by Fracture mechanics, but diverging/converging characteristics of the zones seem to be addressed by Rheology.

- Continuum mechanics could study a plate as a complex system of "brittle/ductile" components. For example, the intra-plate Yellowstone Caldera could be seen as a system of volume of magma locked by plates from bottom, top and other sides. The dynamics of stress pattern around it reflects the caldera behavior.

Refining Geofracture Tectonics.
   The ultimate goal of my posts on Tectonics is not just to reveal the mechanics behind the Tectonic events, but rather to suggest the ideology of modelling the mechanics. The modelling requires special hardware setup, special software over it, but that's the theme for a separate set of posts.
   I don't see how some classic Plate Tectonics terms could be maintained by Geofracture Tectonics, to name a few:

- The timescale with the fancy words like Cenozoic, Mesozoic etc; Rules of Mechanics should not depend of dinosaurs population, instead dinosaurs should depend on mechanics. There is the only time unit - second, To make records shorter, Tera second (Tc) can be used.

- The words asthenosphere, lithosphere seem to be somewhat outdated (my post "Plate Tectonics. Thinking Out Of The Sphere"). Plates are very diverse, plates are completely decoupled from each other by boundaries. Plates can reach depth of many hundreds km, or their thickness can be only few km. I don't see any need to organize the internals of the plates into any artificial the Earth-global entities (spheres) like asthenosphere or lithosphere. The changes of properties of plates with depth that are seen with Geophysics instruments could mark the layers' boundaries. The layers defined this way could be called in plain English, such as "brittle", "ductile", "transition" or similar.
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