Comprehensive Study on Ocean Floor Dynamics

洋底控制着地球内部，特别是地幔的热量和质量的散发。海洋在某种意义上是地球系统中物质流的储存库，地球与地球上部的物质循环有关。众所周知，自150 Ma以来，深海海底沉积物记录了地球系统的动力学历史。因此，对记录的解码将为我们提供新的信息，创造地球科学的新范式。要发展深海海底科学，首先需要从深海中采集岩心样品。第二步是地球化学和地球物理分析，包括年龄测定。三是钻孔物化探测量。最后，我们建立了长期的钻孔观测站，以监测地球内部正在发生的动力学变化，我们的研究小组由五个小组组成，即综合海底动力学小组、俯冲带小组、大洋高原和地幔柱小组、甲烷水合物小组、研究结果表明：1）甲烷水合物的形成、分解、演化过程的新设想，2）极端温暖的气候和生命的大规模灭绝与甲烷水合物的分解密切相关; 3）来自地球外部的热力和动力作用导致千年尺度的环境变化; 4）地表全球环境变化与板块动力学有关; 5）建立了全球钻孔地震台网; 6）在地壳深部细菌生态系统和地球表面物质循环两个领域都有了新的发现

Ocean floor controls an emission of heat and mass from the interior part of the Earth, in particular from mantle. And, ocean acts as a reservoir of mass flux in earth system in a sense, suggesting that the Earth is related to the circulation of mass in the upper part of the Earth.It is well known that history of dynamic earth system has been recorded in deep ocean floor sediments since last 150Ma. Therefore, decoding of the record will provide us new information that creates new paradigm of earth science.In order to develop deep ocean floor science, we need core drilling samples recovered from deep sea as the first step. The second step is characterized by geochemical and geophysical analysis including age determination. The third is in situ geophysical and geochemical measurement in borehole. Finally, we set up long-term borehole observatory in order to monitor ongoing dynamic change of the Earth interior.Our research group is composed following five subgroups such as comprehensive ocean floor dynamics subgroup, subduction zone subgroup, oceanic plateau and mantle plume subgroup, methane hydrate subgroup, and deep biosphere /evolution of life group.The results of our research are listed as follows.1) New scenario regarding to the process of methane hydrate formation, dissociation, and concentration is proposed2) Extremely warm climate and mass extinction of life are closely related to dissociation of methane hydrate3) Millennium scale environmental change is induced by thermal and dynamic impact resulting from outside of globe4) Surface global environmental change is associated with plate dynamics5) Global seismic network using borehole is constructed6) New findings are acquired in both fields of ecosystem of bacteria in deep crust and circulation of surface mass of the Earth