Subaqueous Pyroclastic Flows from Krakatau and Tambora Volcanoes, Indonesia

印度尼西亚的喀拉喀托火山（1883年）和坦博拉火山（1815年）的历史性爆发向海洋排放了超过40公里的火山碎屑物质，其中大部分是大量的重力流。在先前的资助下，通过潜水员部署的取芯系统获得了喀拉喀托火山周围海底沉积物的样本。这项研究的重点是两个短暂的岛屿的起源，Steers和Calmeyer，这两个岛屿是1883年喀拉喀托火山灾难性喷发的结果，形成于喀拉喀托火山的西北部。水下地质填图和沉积物岩心初步检查表明，这两个岛是由海底入口形成的。产生的火山碎屑流流入大海。这些发现为围绕与火山爆发有关的毁灭性海啸的起源以及火山爆发期间喀拉喀托岛的命运的争议提供了新的线索。另外一笔新的经费将用于对1990年收集的样品和坦博拉1815矿床的现有样品进行研究。对水下火山碎屑流沉积物中的浮石和岩屑进行热消磁研究，以确定就位温度，并研究海水在水下运输和沉积过程中的冷却作用。详细的粒度、成分丰度和图像分析也将进行，以评估热火山碎屑流与海水相互作用的性质。这些结果对于了解这些事件砂的喷发过程具有重要意义，为地质记录中的古代收敛边缘序列提供了火山碎屑沉积的现代类似物。

The historic explosive eruptions of Krakatau (1883) and tambora(1815) volcanoes in Indonesia discharged over 40 km 3 of pyroclastic material into the sea, mostly as voluminous gravity flows. With previous funding samples have been obtained of the submarine deposits areound Krakatau volcano by a diver.deployed coring system. The study focussed on the origin of two ephmeral islands, Steers and Calmeyer, that formed to the nortwest of Krakatau as a result of the catastrophic 1883 eruption. Underwater geologic mapping and preliminary examination of sediment cores indicate that the two islands were formed by the entrance of subaerially.generated pyroclastic flows into the sea. The findings have shed new light on the controversy surrounding the origing of devstating tsunamis associated with the eruption and the fate of Krakatau island during the paroxymal stage of the event. New funds for as additional will be used to carry outstudies on the samples collected in 1990 and existing samples of the tambora 1815 deposits. Thermal demagnetization studies on pumice and lithic clasts from the subaqueous pyroclastic flow deposits will be made to determine emplacement temperatures and investigate the role of seawater as colling agent during subaqueous transport and deposition. Detailed grain size, component abundance, and image analysis will also be carried out to evaluate the nature of hot, pyroclastic flow interactions with seawater. These result will be significant in terms of understanding the eruptive processes of these event sand providing modern analogues of volcaniclastic sedimentation that can be applied to ancient convergent margin sequences in the geologic record.