Comprehensive Study on Ocean Floor Dynamics

海底控制着地球内部，特别是地幔的热量和质量的释放。从某种意义上说，海洋在地球系统中充当着质量通量的储存库，这表明地球与地球上部的质量循环有关。众所周知，近150Ma以来，深海海底沉积物中记录了地球动力系统的历史。因此，对记录的解码将为我们提供新的信息，创造新的地球科学范式。为了发展深海海底科学，我们需要从深海中回收岩心钻探样本作为第一步。第二步的特点是地球化学和地球物理分析，包括年龄测定。三是井内地球物理地球化学原位测量。最后，我们建立了长期的钻孔观测站，以监测地球内部的动态变化。本课题组由海底综合动力学课题组、俯冲带课题组、海洋高原与地幔柱课题组、甲烷水合物课题组、深部生物圈/生命演化课题组等5个课题组组成。我们的研究结果如下：1)关于甲烷水合物形成、解离、2)极暖气候和生物大灭绝与甲烷水合物的解离密切相关；3)地球外热动力影响诱发千年尺度的环境变化；4)地表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壳表层物质循环等领域取得了新发现地球

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