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.

跨越太阳系的长期滑坡的侵位机制以及与其沉积物相关的纵向山脊的形成机制仍然存在争议。火星长跳动滑坡的纵向脊与冰上的陆地滑坡的相似性表明，冰冷的表面可以解释与长跳动滑坡的沉积相关的摩擦力的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，冰不是纵向脊发展的必要条件，而纵向脊可能由高速流中的对流单元形成。这些实验表明，脊的波长 (S) 是流动厚度 (T) 的 2-3 倍，这也已在数十公里的火星长跳动山体滑坡上进行了现场规模的证明。在这里，我们展示了智利北部 4 公里长、无冰的 El Magnifico 滑坡的案例研究，该滑坡显示出清晰的纵向脊，并首次在陆地滑坡上表明 S/T 比符合在实验室快速颗粒流和先前测量的火星长跳动滑坡中发现的比例关系。滑坡内的几个露头使我们能够研究滑坡沉积物的内部剖面及其与纵向脊的关系，以阐明就位机制。我们的观察包括不同岩性之间没有混沌混合的相互作用，以及显示保留的原始层理不连续性的米级块体的存在。我们将这些观察结果与应力波动联系起来，因为它们在性质上类似于数值模拟的快速颗粒滑动，这在某种程度上被认为与声学流化有关。我们的研究结果表明：1）形成纵向脊的机制与尺度和环境无关；2）虽然观察到的内部结构不一定支持对流式运动的机制，但他们的解释也可能指向源自模式形成振动的滑动质量的内部变形机制。我们新颖的观察和分析为解释地球和火星上的相似特征以及辨别导致长期滑坡就位的潜在机制提供了重要的见解。