Lithosphere as a Nonlinear System: Geodynamic Consequences

Abstract

1.1 Nonlinear geological medium: theoretical aspect The deterministic viewpoint for natural evolution was dominant in natural sciences for long time. This relates in full measure to geodynamics, and it seems that plate tectonics, being a basis for modern geodynamic conceptions for over 30 years, confirms such viewpoint. The plate tectonics, as a bottom of fact, presents a purely mechanical model based on a simple geometrical observation: the similarity of contours of continents gathered around the Atlantic Ocean. Formerly they composed a single whole, which was broken up and slid apart, to a first approximation, keeping their primary contours. Under this point of view it is meant that geologists deal with the geological environment, being a continuous monolith composed of various solid rocks. This monolith is mechanically divided into different in size fragments (a separate question is a cause of this fragmentation), and the task of tectonic geologists is just to collect the fragments, using their outlines, to reconstruct the history of continents’ movements and development of the oceans and fold belts, and to forecast their further evolution. The plate-tectonic prognosis is taken to be sufficiently determined by the regularities of plate kinematics. The progress of plate tectonics in explanations of many phenomena of the lithosphere structure is obvious, but the question is: what paradigm is going to take its place? This question is even more so appropriate as in the latest quarter of the 20th century the philosophic and methodological conceptions in the field of natural sciences changed from determinism to instability. Works by I. Prigozhin played a great role in the process. The basis of his «philosophy of instability» is dualism [1], stability and instability existing in the universe at the same time. The core of such perception is a thesis about development of highly organized structures in the conditions of nonequilibrium and nonlinear processes in different natural mediums [2, 3, 4]. Nearly three decades have passed since the appearance of instability philosophy, but it is obvious that the introduction of new ideas to geology goes rather slowly. At the same time, during the last two decades of the 20th century, i.e. practically simultaneously with the invention of this new philosophic conception, geophysicists (first of all, seismologists) carried out both experimental and theoretical investigations demonstrated that the medium, with which specialists in the field of the solid Earth deal with, belongs to the mediums characterized by instability and nonlinearity [5, 6, 7]. In essence, a crucially new view on rock characteristic and the whole lithosphere was established, in particular: