Home – Home – Jornals – Russian Geology and Geophysics 2015 number 12

Three levels of the periodicity of volcanic eruptions with different causes and effects are recognized. The first, small-scale, level lasts tens to thousands of years and is due to the periodic accumulation of melt in the intermediate chambers and its periodical effusion both for internal reasons and under the trigger effect of external factors (solar activity, tidal changes in the Earth’s rotation rate). The second, medium-scale, level lasts hundreds of thousands to millions of years and is due to the periodicity of restructuring of spreading and subduction zones. The third, largest-scale and most prolonged, level of periodicity (30-120 Ma) is related to periodic accumulations of melt at the core-mantle boundary, ascent of mantle plumes, and subsequent acceleration of convection. These reasons are probably the major regulator of the average periodicity. Acceleration of convection in the asthenosphere, caused by periodic pulses of mantle jets, determines the changes in the group of moving plates through the changes of spreading zones. The intermediate periodicity level (hundreds of thousands of years to the first millions of years) is demonstrated by the example of Kamchatka and Japan, where the periodic changes in the intensity of subduction magmatism are due to the restructuring of back-arc basins (Shikoku, Sea of Japan, and South Kuril basin).