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.

03 June, 2011

Tectonics. Types Of Heat Transport To Develop Calderas, Volcanoes, And Divergent Boundaries.

   First two types of heat transport are obvious (let's not consider radiation heat transfer): heat conduction and convective heat transfer. And the third type is as described in "Magma Transportation On The Temperature Gradient"

   Third type of heat transport explained.
   The concept of the third type is: Powered by deformations, crust propagates magma in the direction of lower temperature by the means of earthquakes, the magnitude of the earthquakes depends on many factors, among them are: amplitude and frequency of the deformations, crust characteristics, magma temperature, the value of the temperature gradient.

   Many would disagree on the third type. But is not it just a second low of thermodynamics in action? The first two types of heat transport move heat in the direction from higher temperature to lower temperature. Does not do the third type the same, though in its own way?

   No magic, if we have a transition zone between colder solid stuff and molten the same stuff, then, if we apply some chaotic action around the zone, the mother Nature has no choice in its response, other than moving the zone in the direction to colder stuff according to the second low of thermodynamics.

   Of course, the moving of the transition zone causes counter-action: say, gravity can be trying to get the molten stuff back. But don't we know from seismic observations that the magma is pumped up not in the form of some kind of a pipe, but rather in the form of scattered chambers? This way a local deformation has to pump magma between only neighbor chambers. Thus, regardless (almost) of the height of the vertical path, the local force of the deformation needs to be just enough to move magma to a neighbor chamber.

   The more chambers along the vertical path, the greater total force is to be applied. The divergent component of the force has to be compensated, say, in the case of divergent boundaries by subduction counter-force on the opposite side of the plate. The greater counter-force, the higher will be the ridge to build the divergent force to balance the counter-force.

   The third type of heat transport can supply heat and develop pressure on its own with no help from hot spots and plumes.

   The concept of caldera development can be the next:

   - Some inter-plate or an intra-plate instance of the third type of heat transport mechanism is set up.

   - The transition zone on its way to surface meets some horizontally stretched irregularity that helps the transition zone to spread horizontally and blocks (at least for some time) the transition zone from moving up.

   - In the case the irregularity is air, magma is uplifted into the chamber, and we may assume the transition zone is the surface of the uplifted magma, no pressure in the chamber is developing yet. When magma fills the chamber, the transition zone is spreading further (including upward), pressure develops within the zone.

   - In case the irregularity is not air, the transition zone is spreading horizontally, the pressure is developed within the zone.

   - Further a number of scenarios can be suggested:

   Scenario 1. Uplifted magma and molten stuff finds its way out of the chamber forming a volcano outside the area. The pressure drops,  the top of the chamber collapses either at this time or when heat transport stops, say, for the temperature gradient disappeared and the uplifted magma and molten stuff gets down under the plate.

   Scenario 2.  Heat transport is intense and underlying plate is rather thick to maintain high pressure within the transition zone for a long time. There should be created a transition zone chamber between bottom and top plates. The top plate is strong and uniform to let the transition zone propagate uniformly upward within all the chamber area. The propagation, I'd expect to be heard as constant "roaring" as it effectively is a flow of micro earthquakes. When the transition zone is close enough to surface, the chamber blasts, the molten and semi-molten stuff of the chamber gets into air. As the chamber width, I'd expect, could reach a number of plate thicknesses, the amount of the stuff brought into air can be tens, if not hundreds cubic kilometers.

   The transition zone on its way to surface may meet relatively small horizontally stretched irregularity on no irregularity at all. In the latter case I'd expect the transition zone to uplift magma peacefully. The crust deformations would uplift magma until temperature gradient vanishes.

   In the case the transition zone meets some irregularity on its way to surface, the chamber is created. The chamber can store energy in the volume of compressed magma, in the form of compressed gases, in the form of elastic deformations of adjacent crust, etc.  So, when the transition zone finds finally its way to surface, the stored energy helps considerable amount of the transition zone stuff to blast up into air.

   The important point about third type of heat transport mechanism is that it is heat transport mechanism, not exactly magma transport mechanism. Not much deep layer magma is expected to be among the uplifted stuff. And, the distribution of the uplifted stuff per depth it was sourced from, could be figured out. The precision of the estimations is important in crust's deep layers research.
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