Irregular cruśtal but regular mantle movements

Abstract

It is a problem whether the mantle produces mid-oceanic ridges indepedently of crustal conditions or whether inversely regional crustal conditions induce the processes in the mantle that cause the ridges. The author proposes the hypothesis of a mutual influence from both sides. The low-velocity zone is assumed to be a zone of currents which on the one hand depend upon crustal conditions and upon the irregular crustal pattern and on the other hand are causally connected, fed and widely influenced by a regular current system in the mantle. This system is assumed to consist of twelve equisized cells in the lower mantle which are mechanically connected with an inverse system of twenty cells in the upper mantle. The author first published a map of such a system in 1952 (Havemann, 1952), and proposed a dynamics of it (Havemann, 1955). But a satisfactory dynamic connection of crust and system was lacking. The progress of research in the last decade enables the author to propose a solution concerning the contact of near crust and system movements and of the generation of mid-oceanic ridges. The currents of the system are assumed to be moved by chemical as well as by thermal impulses and, therefore, as partly irreversible partly reversible. Geological and geophysical facts and arguments in favour of the theory are discussed. They comprise position and dynamics of large crustal arcs and of ridges causing continental drift; a seismic great circle coinciding with the median circle of a system girdle and its causal connection with Mediterranean movements; satellite-observed anomalies in accordance with the system pattern. The problem of an axis-symmetric system position and of polar wandering is discussed.