Toward a Better Understanding of Magmatic Processes and Volcanic Hazards at Nyiragongo Volcano, DR Congo

尼拉贡戈火山是位于维龙加火山省的一座壮观的活跃层状火山，俯瞰刚果民主共和国戈马市，并在其顶峰火山口拥有世界上最大的熔岩湖。它不同寻常的熔岩是地球上粘性最小的熔岩之一，能够以每小时数十公里的速度移动。尼拉贡戈也是一座危险的火山。它隐约可见，距离戈马和邻国吉塞尼卢旺达的主要人口中心不到20公里，总人口至少为100万。1977年和2002年的破坏性喷发夺走了许多人的生命，摧毁了这个饱受战争蹂躏的地区的基础设施。下一次喷发可能对这一政治动荡和经济困难的地区造成灾难性影响，因此迫切需要为尼拉贡戈的危险评估和减轻风险提供具体的科学框架。关于这座火山的岩浆旋回活动的科学贡献很少，因此，这项研究的主要目标是通过对尼拉贡戈主锥和外围火山锥的熔岩样品进行年龄测定来提供过去喷发的时间结构，这是特别危险的，因为它们靠近戈马人口，许多锥体居住在城市范围内。调查结果将分发给最终用户、戈马及其周围地区的居民。合作者达里奥·特德斯科多年来一直与戈马火山观测站和联合国密切合作，解决刚果民主共和国的火山灾害问题，他将推动这一目标的实现。除了这一危险评估部分，这项研究还将侧重于对尼拉贡戈火山喷发的极不寻常的熔岩提出的基础科学问题。这项研究不仅将有助于了解尼拉贡戈火山熔岩流的来源和演化，而且还将为类似火山过程的全球研究提供重要的终端成员。由于所有这些原因，这项工作将得到NSF国际科学与工程部门的部分支持。这项研究的两个明确目标涉及1)危险评估和2)基础科学问题。实现第一个目标的主要方式是使用40Ar/39Ar、14C和U衰变系列同位素对尼拉贡戈的熔岩流和寄生锥体进行精确的年龄测定。尼拉贡戈过去喷发的时间框架将从2010年收集的熔岩年龄和尼拉贡戈熔岩流和寄生锥体的关键新样本中获得，这些新样本将在随后的实地考察中收集。第二个目标是加强对尼拉贡戈碱性硅质不饱和岩浆作用的来源、过程和时间尺度的基本科学了解。然后，这些结果将与尼拉贡戈高度活跃的姊妹火山尼亚穆拉吉拉进行的单独和平行的研究，以及来自全球其他碱性火山群的数据进行比较。这一目标将通过测量2010年从尼拉贡戈熔岩湖采集的年轻的已知年龄的熔岩中的常量和微量元素、放射性成因的Nd、Sr、Hf和Pb同位素以及长寿和短寿的U和Th衰变系列同位素来实现。

Nyiragongo is a spectacular, active stratovolcano in the Virunga Volcanic Province that towers over the city of Goma, Democratic Republic of the Congo (DR Congo), and hosts the world's largest lava lake in its summit crater. Its unusual lavas are some of the least viscous on the planet and are capable of moving at velocities of up to tens of kilometers per hour. Nyiragongo is also a dangerous volcano. It looms within 20 km of the major population centers of Goma and neighboring Gisenyi Rwanda, with a combined population of at least 1 million. Destructive eruptions in 1977 and 2002 claimed many lives and devastated infrastructure in this war torn region. The next eruption could prove disastrous in this politically volatile and economically challenged area and there is consequently an urgent need to provide a concrete scientific framework for hazard assessment and risk mitigation at Nyiragongo. There is a dearth of scientific contributions that address magmatic cyclicity at this volcano and thus the primary goal of this research is to provide a temporal structure of past eruptions by age dating lava samples from Nyiragongo's main cone and from peripheral volcanic cones, which are especially dangerous because of their proximity to the population of Goma, with many cones residing within the city limits. Findings will be disseminated to the end-users, the residents of Goma and surroundings. Collaborator Dario Tedesco, who for many years has worked closely with the Goma Volcano Observatory and the United Nations addressing the volcanic hazards in the DR Congo, will facilitate this goal. In addition to this hazard assessment component, this research will focus on basic science queries about the highly unusual lavas that erupt at Nyiragongo. Not only will this study contribute to the understanding of the sources and evolution of lava flows at Nyiragongo, but it will also provide an important end-member in global studies of similar volcanic processes. For all of these reasons, this work will be supported in part by NSF's International Science and Engineering Section.The two explicit goals of this research involve 1) hazard assessment and 2) basic science questions. The primary way in which the first goal will be accomplished is through precise age dating of lava flows and parasitic cones from Nyiragongo using 40Ar/39Ar, 14C, and U decay series isotopes. A more complete temporal framework of past eruptions at Nyiragongo will be gained from these age dates from lavas collected in 2010 and critical new samples from Nyiragongo's lava flows and parasitic cones that will be collected in an ensuing field campaign. The second goal is to enhance basic scientific understanding of the sources, processes and timescales associated with the petrogenesis of the alkaline, silica-undersaturated magmatism at Nyiragongo. These results will then be compared with a separate and parallel study of Nyiragongo's highly active sister volcano Nyamulagira, as well as data from other alkaline volcanic suites around the globe. This goal will be accomplished through the measurement of major- and trace- elements, radiogenic Nd, Sr, Hf and Pb isotopes and both long- and short-lived U and Th decay series isotopes in young, known age lavas collected from Nyiragongo's lava lake in 2010.