Implications of longitudinal ridges for the mechanics of ice-free long runout landslides
Implications of longitudinal ridges for the mechanics of ice-free long runout landslides
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DOI：
10.1016/j.epsl.2021.117177
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发表时间：
2021-11
影响因子：
5.3
通讯作者：
G. Magnarini;T. Mitchell;L. Goren;P. Grindrod;John Browning
中科院分区：
文献类型：
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作者：
G. Magnarini;T. Mitchell;L. Goren;P. Grindrod;John Browning
横跨太阳系的长距离滑坡的就位机制和与其沉积物相关的纵向脊的形成机制仍然是争论的主题。火星长距离滑坡和陆地滑坡在冰上的纵向脊的相似性表明，冰表面可以解释与长距离滑坡沉积相关的摩擦力减少和纵向脊的发展。然而，对快速颗粒流的实验室实验表明，冰并不是纵向脊发展的必要条件，而是可能由高速流动中的对流单元形成。这些实验表明，脊的波长（S）是流动厚度（T）的2-3倍，这也在数十公里的火星长径流滑坡的现场规模上得到了证明。在这里，我们提出了4公里长的，无冰的萨尔瓦多Magnifico滑坡在智利北方，具有清晰的纵向脊的案例研究，并首次显示在陆地滑坡的S/T比是在实验室快速颗粒流和以前测量的火星长径流滑坡的比例关系。滑坡内的几个露头使我们能够研究滑坡存款的内部部分及其与纵向山脊的关系，以阐明侵位机制。我们的观察结果包括相互作用，没有混乱的混合不同的岩性和存在的米大小的块，表现出保存原始层理不连续性。我们将这些观察结果与应力波动相关联，因为它们在质量上类似于数值模拟的快速颗粒状幻灯片，这在某种程度上被认为与声流化有关。我们的研究结果表明，1）负责形成纵向脊的机制是规模和环境无关的; 2）虽然观察到的内部结构不一定支持对流型运动的机制，他们的解释也可以指向来自模式形成振动的滑动体的内部变形的机制。我们新颖的观测和分析为解释地球和火星上的类似特征以及辨别长期滑坡的潜在机制提供了重要的见解。
The emplacement mechanisms of long runout landslides across the Solar System and the formation mechanisms of longitudinal ridges associated with their deposits remain subjects of debate. The similarity of longitudinal ridges in martian long runout landslides and terrestrial landslides emplaced on ice suggests that an icy surface could explain both the reduction of friction associated with the deposition of long runout landslides and the development of longitudinal ridges. However, laboratory experiments on rapid granular flows show that ice is not a necessary requirement for the development of longitudinal ridges, which instead may form from convective cells within high-speed flows. These experiments have shown that the wavelength (S) of the ridges is 2-3 times the thickness (T) of the flow, which has also been demonstrated at field scale on a tens-of-kilometre martian long runout landslide. Here, we present the case study of the 4-km-long, ice-free El Magnifico landslide in Northern Chile which exhibits clear longitudinal ridges, and show for the first time on a terrestrial landslide that the S/T ratio is in agreement with the scaling relationship found for both laboratory rapid granular flows and a previously measured martian long runout landslide. Several outcrops within the landslide allow us to study internal sections of the landslide deposit and their relationship with the longitudinal ridges in order to shed light on the emplacement mechanism. Our observations include interactions without chaotic mixing between different lithologies and the presence of meters-sized blocks that exhibit preserved original bedding discontinuities. We associate these observations with fluctuations in stress, as they are qualitatively similar to numerically modelled rapid granular slides, which were suggested, to some degree, to be associated with acoustic fluidization. Our results suggest that 1) the mechanism responsible for the formation of longitudinal ridges is scale- and environment-independent; 2) while the internal structures observed do not necessarily support a mechanism of convective-style motion, their interpretation could also point to a mechanism of internal deformation of the sliding mass derived from pattern-forming vibrations. Our novel observations and analysis provide important insights for the interpretation of similar features on Earth and Mars and for discerning the underlying mechanisms responsible for the emplacement of long run out landslides.