No rock is accidental.
No idea in geology is more profound than this; it runs from the center to the whole of geology and influences every sub-discipline of the field. Genuine understanding of the science of geology begins with one’s ability to understand and explain why no rock is accidental.It Is concerned with deformation in the earth and the forces that produce deformation. Plate tectonics is the theory that the earth’s Plate tectonics is one of the great unifying theories in geology. Virtually every part of the earth’s crust, and every kind of rock and every kind of geology can be related to the plate tectonic conditions that existed at the time they formed.
Nothing in geology makes sense except in terms of plate tectonic theory.
One of the most important messages of modern understanding of plate tectonics and the Wilson cycle is that beginning with a parent igneous rock of mafic/ultramafic composition all the other rocks now on the earth can be generated. The most important message of the plate tectonic rock cycle is that each and every rock forms only under a specific set of tectonic conditions.
Divergent boundaries where plates are moving apart, and new crust is being created,
Convergent boundaries where plates are moving together and crust is being destroyed, and
Transform boundaries where plates slide past one another
There are two models summarizing earth evolutionary processes.
(1) The Wilson Cycle and
2 )Tectonic Rock Cycle, a more theoretically abstact model of how rocks and the earth evolve.
Wilson Cycle model follows the series of cross sections constituting the Wilson cycle. It begins with a hypothetical geologically (tectonically) quiet continent. The model is divided into nine stages, but the stages are arbitrary and do not exist naturally. The earth is an ongoing series of processes so it is much more important to understand the processes, how they are related, and how one process leads naturally to the next process.
Wilson Cycle is a simple, ideal model. The earth has many continents, which migrate across its spherical surface in very complex ways. Just about any scenario you can think of, and any exception you can imagine is quite possible – and has probably happened during some point in the earth’s history.
Lithosphere (outer rigid shell) is composed of several dozen “plates”, or pieces, which float on a ductile mantle, like slabs of ice on a pond. In plate tectonic theory earth history, at its simplest, is one of plates rifting into pieces diverging apart and new ocean basins being born, followed by motion reversal, convergence back together, plate collision, and mountain building. This cycle of opening and closing ocean basins is the Wilson Cycle.