Origin of spectacular fields of submarine sediment waves around volcanic islands
Origin of spectacular fields of submarine sediment waves around volcanic islands
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DOI：
10.1016/j.epsl.2018.04.020
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发表时间：
2018-07
影响因子：
5.3
通讯作者：
E. Pope;M. Jutzeler;M. Cartigny;J. Shreeve;P. Talling;I. Wright;R. Wysoczanski
中科院分区：
文献类型：
--
作者：
E. Pope;M. Jutzeler;M. Cartigny;J. Shreeve;P. Talling;I. Wright;R. Wysoczanski
了解火山岛侧面的海底形态和沉积物如何记录大规模喷发和山体滑坡对于重建火山岛历史和地质灾害评估非常重要。最近，人们在世界各地多个地点的火山岛水下侧翼发现了壮观的地床形态。这些河床形态可延伸50多公里，个别河床长度可达3公里，高度可达150米。然而，人们对这些床形场的起源知之甚少。在这里，我们表明，某些地点的地床形态是由喷发供给的超临界密度流（浊流）造成的，但在其他地点很可能是旋转山体滑坡。提供了区分由火山喷发和滑坡形成的海底地床形态的一般标准，并强调需要高分辨率地震数据集以防止歧义。与旋转滑坡相关的地床形态具有较窄的来源，具有明显的头顶，它们更受横向限制，并且内部床形结构并不表明每个床形都向上坡迁移。喷发产生的密度流产生了广阔的地床形态，从火山口呈放射状延伸。详细地震数据成像的内层显示，这些地床形态向上倾斜，表明产生它们的流动是弗劳德超临界流动。由于间质液和沉积物之间的密度对比较低，海底喷发形成的地床形状的范围和尺寸远大于陆地上火山碎屑密度流产生的地床形状。
Understanding how large eruptions and landslides are recorded by seafloor morphology and deposits on volcanic island flanks is important for reconstruction of volcanic island history and geohazard assessment. Spectacular fields of bedforms have been recognised recently on submerged flanks of volcanic islands at multiple locations worldwide. These fields of bedforms can extend over 50 km, and individual bedforms can be 3 km in length and 150 m in height. The origin of these bedform fields, however, is poorly understood. Here, we show that bedforms result from eruption-fed supercritical density flows (turbidity currents) in some locations, but most likely rotational landslides at other locations. General criteria are provided for distinguishing between submarine bedforms formed by eruptions and landslides, and emphasise a need for high resolution seismic datasets to prevent ambiguity. Bedforms associated with rotational landslides have a narrower source, with a distinct headscarp, they are more laterally confined, and internal bedform structure does not suggest upslope migration of each bedform. Eruption-fed density currents produce wide fields of bedforms, which extend radially from the caldera. Internal layers imaged by detailed seismic data show that these bedforms migrated up-slope, indicating that the flows that produced them were Froude supercritical. Due to the low density contrast between interstitial fluid and sediment, the extent and dimensions of submarine eruption-fed bedforms is much greater than those produced by pyroclastic density currents on land.