Terrestrial Palaeoecology and Global Change

Chapter 10. Conclusions
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X. CONCLUSIONS
The global change of our lifetime experience is partly man-made, partly natural. How
much of it is natural can be inferred from pre-historic records. If, as the records seem to
suggest, the changes are cyclic, it will be useful to know at what stage of a cycle we are
at the moment. One guess is as good as another until we arrive at a general if but crude
model of complex interactions that drive evolution of biosphere as a geobiological system.
The model would encompass the multilevel developments from the geoid to the
genome, but as interrelated aspects of a singular story rather than separate stories. The
book presents an attempt at such a model from a viewpoint of a palaeoecologist.
The role of biosphere in the global change is a stabilizing one, and it will be potentially
even more so with an addition of the rational human factor. However, the biosphere, for
all its significance, is a thin film stretched and occasionally ruptured by the deep breath of
the earth. The breath is rhythmic, paced by the earth’s rotation and revolution, with
autocyclic and induced fluctuations creating a hierarchical cyclicity. Periodic gravitational
disturbance of the time-scale of the Galactic Year are such as should be inflicted by
the huge concentrations of interstellar matter that are encountered by the solar system
on its eccentric orbit round the centre of the Galaxy (V.2). The shorter-term rotational
perturbations are relatively well known and are the most obvious driving force of the
global change.
The atmospheric and hydrospheric circulations are driven by the rotational forcing
that acts upon the solid earth as well. That the latter effect is far from being negligible
is immediately evident form a glimpse at the transcurrent fault system cutting across
the mid-ocean ridges and their parallel lineaments: their brocken-stick outlines show
maximal displacement at the equator. A rotational origin of the global fault network is
beyond any reasonable doubt as is the physical necessity of a discrepant rotational
acceleration over the density heterogeneities, such as the continental and oceanic crust
domains or the interior divisions of the earth’s core, mantle and lithosphere. The
boundaries of the continents with the denser oceanic crust are the shear zones of a
vigorous tectonic and igneous activity creating the global fold belts. Friction melting at
the interior density boundaries generates magmatic sources as well as perturbations of
the geomagnetic field.
However the rotational acceleration inflicts not only the lateral but also the radial
shear. The centrifugal component of rotational acceleration of plus or minus sign drives,
respectively, a divergence or convergence of hypsometric levels for the isostatically
compensated oceanic and continental crust resulting in an alternation of geocratic (high
standing continents – deep oceans) and talassocratic (low continents – shallow oceans)
situations. Insofar as a segment of lithosphere expands while it is raised, the geocratic
tendencies are correlated with a continental rifting and trap magmatism, whereas the
sea-floor magmatism increases during the talassocratic epochs.