History of large magnitude explosive volcanism in the Japan region: implications for tectonics and long term hazards

海洋钻探在世界各地都有发生，这使得科学家们可以检查数百万年前海底的沉积物。岩心（实际上是一个充满沉积物的排水管）在整个研究探险中被钻取，一直延伸到海底的沉积物和岩石中。这些岩心通常含有火山灰层，这为重建大型火山爆发的历史提供了主要资源。在日本九州地区，陆地上的火山记录与构造板块重建的对比（Mahony et al., 2011）表明，火山活动方式的重大变化与构造板块运动方向和速度的变化发生在相似的时间。国际海洋发现计划（IODP）的第350次探险提供了一个绝佳的机会来检验这些显著变化的假设，推进对成因构造和火山过程的理解，评估保护海洋灰层的因素，并整合这些研究来阐明构造和大震级爆发之间的关系。本研究的目的是回答以下问题：-爆炸性火山活动的速率是否与板块构造行为有关？-是什么导致了这些关系？-就潜在的岩浆活动而言，大震级火山喷发记录的意义是什么？为了回答这些问题，IODP远征350期间钻探的一系列火山灰层将被采集样本并进行分析。首先，将通过观察火山灰的化学成分来确定喷发源、火山或火山灰产生的地区。接下来，将研究每个火山灰层中火山颗粒的大小，以确定颗粒大小、火山灰层厚度、与源火山的距离以及产生火山灰层的喷发强度之间是否存在相关性。对与灰层厚度变化有关的不确定度的分析也将进行研究。最后，所有这些信息将被整合，以检验研究的目的。这项研究的一个最终目标是对大规模爆发的重现期及其伴随的不确定性提供估计。诸如此类的研究对于易受极端火山事件影响的敏感设施（例如核电站）的选址非常重要。参考文献：Mahony， s.h., Wallace, l.m., Miyoshi， M, Villamor， P, Sparks， R.S.J. & Hasenaka， T. 2011。日本西南部九州地区板块边界快速演化过程中的火山-构造相互作用。青烟。Soc。点。学报，23,221 -2223。

Ocean drilling occurs all around the world, and allows scientists to examine sediments that were on the ocean floor many millions of years ago. Cores (effectively of a drain pipe full of sediment) are drilled throughout research expeditions, extending several kilometres down into the sediments and rocks on the ocean floor. These cores often contain volcanic ash layers, which provide a major resource to reconstruct the history of large volcanic eruptions. In the Kyushu region of Japan, comparison of volcanic records on land with tectonic plate reconstructions (Mahony et al., 2011) shows that major changes in the style of volcanic activity occurred at a similar time to changes in the direction and rate of tectonic plate motion. International Ocean Discovery Program (IODP) Expedition 350 provides an outstanding opportunity to test hypotheses for these marked changes, to advance understanding of the causative tectonic and volcanic processes, assess factors that preserve marine ash layers, and to integrate these studies to elucidate the relationship between tectonics and large magnitude explosive eruptions.The aims of this study are to answer the following questions: - Can rates of explosive volcanism be related to plate tectonic behaviour?- What causes these relationships?- What is the significance of a record of large magnitude volcanic eruptions in terms of the underlying magmatic activity?To answer these questions, a series of volcanic ash layers drilled during IODP Expedition 350 will have samples taken and analysed. First, the source eruption, volcano or region the ash originated from will be identified by looking at the chemistry of the volcanic ash. Next the size of volcanic particles in each ash layer will be studied, to establish is there is a correlation between the grain sizes, the thickness of the ash layer, the distance from the source volcano, and the magnitude of the eruption which produced the ash layer. Analysis of the uncertainty related to variations in ash layer thickness will also be investigated. Finally all of this information will be integrated to test the study aims. One ultimate goal of the research is to provide estimates of the return periods of large magnitude explosive eruptions and their attendant uncertainties. Studies such as these are important for the siting of sensitive facilities vulnerable to extreme volcanic events (e.g. nuclear power stations). References:Mahony, S.H., Wallace, L.M., Miyoshi, M, Villamor, P, Sparks, R.S.J. & Hasenaka, T. 2011. Volcano-tectonic interactions during rapid plate-boundary evolution in the Kyushu region, SW Japan. Geol. Soc. Am. Bull, 123, 2201-2223.