On the origin of recent and modern vertical movements in the island systems of northeastern Asia

Abstract

The paper deals with recent and modern vertical movements in the island systems of East Asia (Kamchatka, Sakhalin and Japan). It is shown that recent and modern deformations of the earth's surface are often correlated with geological structures and are inherited from more ancient movements. Slow (secular) movements in reality change their sign within short periods of time and are similar in this respect to rapid (impulsive) movements. Often inversion occurs in the areas of neotectonic uplifts. Comparison of the crustal deformations and gravity anomalies suggests that positive vertical movements are accompanied by mass supply into the earth's crust. It is also revealed that both modern and neotectonic uplifts are often accompanied by electrically conductive layers that are present in some regions at depths of 10–15 km. All these features of the vertical movements, together with quantitative estimations of the sources of vertical deformations, allow us to conclude that they are caused by intermittent magma inflow from the mantle and its intrusion at predominantly two levels: one in the upper mantle near the lower crustal boundary, where zones of partial melting are formed, and the other at depths of 10–15 km in the crust. They occur both at deeper and shallower levels, causing a complex range of vertical movements of various wavelengths. The mechanism of magma uplift seems to be related to its excess pressure, leading to the formation of tension fractures. Some phenomena accompanying crustal magmatism are briefly discussed. The conclusion is drawn that the above mechanism of vertical movements may be widespread in the intra-plate regions at least.