What determines the downstream evolution of turbidity currents?
What determines the downstream evolution of turbidity currents?
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DOI：
10.1016/j.epsl.2019.116023
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发表时间：
2020-02-15
影响因子：
5.3
通讯作者：
Pope, Edward
中科院分区：
文献类型：
--
作者：
Heerema, Catharina J.;Talling, Peter J.;Pope, Edward
被称为浊流的海底沉积物流动形成了地球上一些最大的沉积物堆积、最深的峡谷和最长的河道系统。只有河流能在如此大的区域内搬运相当数量的沉积物；但是对浊流的测量要少得多，这导致人们对其了解少得多。浊流与河流有根本的不同，因为浊流是由其所悬浮的沉积物驱动的。快速的浊流能够卷起沉积物，并自我加速（激发）；而缓慢的流动则沉积沉积物并消散。自我加速不可能无限持续，流动可能会达到一种近乎均匀的状态（自动悬浮）。在这里，我们利用来自加利福尼亚近海蒙特雷峡谷其路径上多个位置的首次详细测量结果，展示了浊流是如何演变的。所有的流动最初都会激发。通常，最初速度较快的流动随后会达到近乎均匀的速度（自动悬浮），而较慢的流动则会消散。初始速度的微小增加有利于更长的流动距离，一个新的模型解释了这种分叉行为。然而，在风暴较少的夏季月份出现的唯一一次流动是异常的，因为它自我加速了，这可能是由于峡谷中部表层泥层的侵蚀。因此，浊流的演变对初始速度和海底特征都高度敏感。（C）2019年由爱思唯尔出版社出版
Seabed sediment flows called turbidity currents form some of the largest sediment accumulations, deepest canyons and longest channel systems on Earth. Only rivers transport comparable sediment volumes over such large areas; but there are far fewer measurements from turbidity currents, ensuring they are much more poorly understood. Turbidity currents differ fundamentally from rivers, as turbidity currents are driven by the sediment that they suspend. Fast turbidity currents can pick up sediment, and self-accelerate (ignite); whilst slow flows deposit sediment and dissipate. Self-acceleration cannot continue indefinitely, and flows might reach a near-uniform state (autosuspension). Here we show how turbidity currents evolve using the first detailed measurements from multiple locations along their pathway, which come from Monterey Canyon offshore California. All flows initially ignite. Typically, initially-faster flows then achieve near-uniform velocities (autosuspension), whilst slower flows dissipate. Fractional increases in initial velocity favour much longer runout, and a new model explains this bifurcating behaviour. However, the only flow during less-stormy summer months is anomalous as it self-accelerated, which is perhaps due to erosion of surficial-mud layer mid-canyon. Turbidity current evolution is therefore highly sensitive to both initial velocities and seabed character. (C) 2019 Published by Elsevier B.V.