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

尼拉贡戈火山位于维龙加火山省，是一座壮观的、活跃的层状火山，耸立在刚果民主共和国的戈马市之上，其山顶火山口拥有世界上最大的熔岩湖。它不寻常的熔岩是地球上最不粘稠的熔岩之一，能够以每小时数十公里的速度移动。尼拉贡戈火山也是一座危险的火山。它距离戈马和邻近的卢旺达吉塞尼的主要人口中心不到20公里，这两个城市加起来至少有100万人口。1977年和2002年的毁灭性火山爆发夺去了许多人的生命，并摧毁了这个饱受战争蹂躏的地区的基础设施。在这个政治动荡和经济困难的地区，下一次喷发可能是灾难性的，因此迫切需要为尼拉贡戈火山的危害评估和减轻风险提供一个具体的科学框架。关于这座火山岩浆旋回性的科学研究还很缺乏，因此这项研究的主要目标是通过对尼拉贡戈火山主要火山锥和外围火山锥的熔岩样本进行年龄测定来提供过去火山喷发的时间结构，这些火山锥由于靠近戈马人口而特别危险，许多火山锥居住在城市范围内。调查结果将分发给最终用户、戈马居民和周围地区。合作者达里奥·特德斯科（Dario Tedesco）多年来一直与戈马火山观测站和联合国密切合作，应对刚果民主共和国的火山灾害，他将促进这一目标的实现。除了这个危险评估部分，这项研究将集中在尼拉贡戈火山喷发的非常不寻常的熔岩的基础科学问题上。这项研究不仅有助于了解尼拉贡戈火山熔岩流的来源和演化，而且还将为全球类似火山过程的研究提供一个重要的终点。由于所有这些原因，这项工作将得到美国国家科学基金会国际科学与工程部的部分支持。这项研究的两个明确目标包括1)危害评估和2)基础科学问题。实现第一个目标的主要方法是使用40Ar/39Ar、14C和U衰变系列同位素对尼拉贡戈火山的熔岩流和寄生锥进行精确的年龄测定。对尼拉贡戈火山过去喷发的一个更完整的时间框架，将从2010年收集的熔岩的年龄数据，以及在随后的野外活动中收集的尼拉贡戈火山熔岩流和寄生锥的关键新样本中获得。第二个目标是加强对尼拉贡戈碱性、硅质欠饱和岩浆成因的来源、过程和时间尺度的基本科学认识。然后，这些结果将与尼拉贡戈火山高度活跃的姊妹火山尼亚穆拉吉拉火山的独立平行研究以及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年从尼拉贡戈火山熔岩湖收集的已知年龄的年轻熔岩中的主要元素和微量元素、放射性Nd、Sr、Hf和Pb同位素以及长期和短期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.