On 25th January 2019, the tailings dam of the Brumadinho iron mine operated by Vale S/A failed catastrophically. The death toll stood at 259 and 11 people remained missing as of January 2020. This tragedy occurred three years after Mariana’s tailings dam rupture – the most significant tailing dam disaster in Brazilian history. Thus far, a systematic investigation on the cause and effect of the failure has yet to be conducted. Here, we use satellite-driven soil moisture index, multispectral high-resolution imagery and Interferometric Synthetic Aperture Radar (InSAR) products to assess pre-disaster scenarios and the direct causes of the tailings dam collapse. A decreasing trend in the moisture content at the surface and the full evanescence of pond water through time (2011–2019) suggest that the water was gradually penetrating the fill downwards and caused the seepage erosion, saturating the tailings dam. Large-scale slumping of the dam (extensional failure) upon the rupture indicates that the materials of the fill were already saturated. InSAR measurements reveal a dramatic, up to 30 cm subsidence in the dam (at the rear part) within the past 12 months before the dam collapse, signifying that the sediments had been removed from the fill. Although the information on the resistance level of the tailings dam to infiltrations is not available, these pieces of evidence collectively indicate that the seepage erosion (piping) is the primary cause for the chronic weakening of the structure and, hence, the internal “liquefaction” condition. Upon the collapse, the fully saturated mud tailings flowed down the gentle slope area (3.13 × 10⁶ m²), where 73 % were originally covered by tree, grass or agricultural tracts. The toxic mud eventually reached the Paraopeba River after travelling 10 km, abruptly increasing the suspended particulate matter (SPM) concentration and the toxic chemical elements in the river, immediately affecting the local livelihoods that depend on its water. The Paraopeba River is a major tributary of the San Francisco River, the second-longest river in Brazil reaching the Atlantic Ocean. We anticipate that the environmental repercussions of this toxic seepage will be felt throughout the entire basin, especially riverine communities located downstream.

2019年1月25日，Vale S / A运营的Brumadinho铁矿的尾矿坝灾难性地倒塌。截至2020年1月，死亡人数为259人，仍有11人失踪。这一悲剧发生在马里亚纳的尾矿坝破裂三年之后-这是巴西历史上最严重的尾矿坝灾难。迄今为止，尚未对故障的原因和后果进行系统的调查。在这里，我们使用卫星驱动的土壤湿度指数，多光谱高分辨率图像和干涉合成孔径雷达（InSAR）产品来评估灾前情景以及尾矿坝坍塌的直接原因。随着时间的推移（2011-2019年），表层水分含量下降，池塘水逐渐消失，这表明水逐渐向下渗透填充物并引起渗漏侵蚀，使尾矿坝饱和。破裂时大坝的坍塌（延伸破坏）表明填充物的材料已经饱和。InSAR测量显示，在大坝坍塌之前的过去12个月中，大坝（在后部）的沉陷程度高达30厘米，这表明沉积物已从填埋物中清除。尽管无法获得有关尾矿坝对渗透的抵抗力水平的信息，但这些证据共同表明，渗流侵蚀（管道）是结构长期削弱的主要原因，因此，内部“液化”状态。坍塌后，完全饱和的泥矿尾矿顺着缓坡区流下（3.13×10⁶  m ²），其中73％最初被树木，草丛或农用地覆盖。有毒泥浆在行驶10公里后最终到达Paraopeba河，这突然增加了河流中的悬浮颗粒物（SPM）浓度和有毒化学元素，立即影响了依赖其水的当地生计。帕拉欧佩巴河是旧金山河的主要支流，旧金山是巴西第二大河，直达大西洋。我们预计，在整个流域，特别是下游的河流社区，都会感受到这种有毒渗漏的环境影响。