Complex and Cascading Triggering of Submarine Landslides and Turbidity Currents at Volcanic Islands Revealed From Integration of High-Resolution Onshore and Offshore Surveys
Complex and Cascading Triggering of Submarine Landslides and Turbidity Currents at Volcanic Islands Revealed From Integration of High-Resolution Onshore and Offshore Surveys
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DOI：
10.3389/feart.2018.00223
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发表时间：
2018-09
影响因子：
2.9
通讯作者：
M. Clare;T. Le Bas;D. Price;J. Hunt;D. Sear;M. Cartigny;A. Vellinga;W. Symons;C. Firth;S. Cronin
中科院分区：
文献类型：
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作者：
M. Clare;T. Le Bas;D. Price;J. Hunt;D. Sear;M. Cartigny;A. Vellinga;W. Symons;C. Firth;S. Cronin
火山岛的水下侧翼容易遭受多种灾害，包括可能引发破坏性海啸以及含泥沙的海底流（称为“浊流”）的海底滑坡。这些灾害可能破坏对全球通信和能源传输至关重要的海底基础设施。小岛屿发展中国家由于地处偏远、孤立，面积小，人口密度高以及经济薄弱，特别容易受到这些灾害的影响。尽管它们很脆弱，但针对此类岛屿的详细近海勘测却很少，这导致了一个地质灾害“盲点”，在南太平洋地区尤其如此。了解这些灾害是如何被触发的很重要；然而，确定具体的触发因素具有挑战性，因为大多数研究无法将陆上和近海环境连续联系起来，并且主要关注突然产生大量泥沙的大规模火山喷发。在这里，我们聚焦于一个火山泥沙供应量高的区域，该区域也类似于（无论是否是火山地区）因人类导致的植被变化而使泥沙过度供应到海岸边缘的地点。我们通过整合从瓦努阿图的塔纳岛获取的首份详细的（2米×2米）测深数据，并结合陆地遥感数据、陆上和近海泥沙采样以及有记录的历史事件来解决这些问题。塔纳岛上的亚苏尔火山至少在过去600年里经历了低强度的斯特龙博利式活动。我们发现了海底滑坡和浊流的明确证据，但与之前几项研究的结论相反，所确定的触发因素都与重大火山喷发无关。相反，我们发现一连串非火山事件（包括流量大于1000立方米/秒的突发洪水以及热带气旋）可能更为重要，这些事件可能相隔数十年，它们对于像塔纳岛这样泥沙供应过剩的沉积环境中的滑坡和浊流的预处理和触发更为关键。最后，我们得出了一个关于海底滑坡和浊流在火山岛以及其他侵蚀严重的山地岛屿上是如何被触发的通用模型。我们的模型强调了突发洪水常被忽视的重要性、对土地利用和气候变化的非线性响应，以及一系列可能掩盖火山活动的海岸和构造过程之间的复杂相互作用。
Submerged flanks of volcanic islands are prone to hazards including submarine landslides that may trigger damaging tsunamis and sediment-laden seafloor flows (called ‘turbidity currents’). These hazards can break seafloor infrastructure which is critical for global communications and energy transmission. Small Island Developing States are particularly vulnerable to these hazards due to their remote and isolated nature, small size, high population densities and weak economies. Despite their vulnerability, few detailed offshore surveys exist for such islands, resulting in a geohazard ‘blindspot’, particularly in the South Pacific. Understanding how these hazards are triggered is important; however, pin-pointing specific triggers is challenging as most studies have been unable to link continuously between onshore and offshore environments, and focus primarily on large-scale eruptions with sudden production of massive volumes of sediment. Here we focus on an area with a high volcanic sediment supply, which is also similar to locations (volcanic or not) where human-induced vegetation change over-supplies sediments to coastal margins. We address these issues by integrating the first detailed (2 m x 2 m) bathymetry data acquired from Tanna Island, Vanuatu with a combination of terrestrial remote sensing data, onshore and offshore sediment sampling, and documented historical events. Mount Yasur on Tanna has experienced low-magnitude Strombolian activity for at least the last 600 years. We find clear evidence for submarine landslides and turbidity currents, yet none of the identified triggers are related to major volcanic eruptions, in contrast to conclusions from several previous studies. Instead we find that cascades of non-volcanic events (including outburst floods with discharges of >1000 m3/s, and tropical cyclones), that may be separated by decades, are more important for preconditioning and triggering of landslides and turbidity currents in oversupplied sedimentary regimes such as at Tanna. We conclude with a general model for how submarine landslides and turbidity currents are triggered at volcanic and other heavily eroding mountainous islands. Our model highlights the often-ignored importance of outburst floods, non-linear responses to land-use and climatic changes, and the complex interactions between a range of coastal and tectonic processes that may overshadow volcanic regimes.