The southeastern flank of Etna volcano slides into the Ionian Sea at rates of centimeters per year. The prevailing understanding is that pressurization of the magmatic system, and not gravitational forces, controls flank movement, although this has also been proposed. So far, it has not been possible to separate between these processes, because no data on offshore deformation were available until we conducted the first long-term seafloor displacement monitoring campaign from April 2016 until July 2017. Unprecedented seafloor geodetic data reveal a >4-cm slip along the offshore extension of a fault related to flank kinematics during one 8-day-long event in May 2017, while displacement on land peaked at ~4 cm at the coast. As deformation increases away from the magmatic system, the bulk of Mount Etna's present continuous deformation must be driven by gravity while being further destabilized by magma dynamics. We cannot exclude flank movement to evolve into catastrophic collapse, implying that Etna's flank movement poses a much greater hazard than previously thought. The hazard of flank collapse might be underestimated at other coastal and ocean island volcanoes, where the dynamics of submerged flanks are unknown.

中文翻译：

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埃特纳火山东南侧面的引力坍塌。

埃特纳火山东南翼以每年厘米的速度滑入爱奥尼亚海。普遍的理解是，尽管也有人提出，对岩浆系统加压而不是重力来控制侧翼运动。到目前为止，尚无法在这两个过程之间进行区分，因为直到2016年4月至2017年7月我们进行了首次长期海底位移监测运动之前，尚无有关海上变形的数据。前所未有的海底大地测量数据显示> 4在2017年5月的一次为期8天的事件中，沿与侧面运动学有关的断层的近海延伸滑移了1厘米，而陆地上的位移在海岸约4厘米处达到峰值。随着形变远离岩浆系统，埃特纳火山的大部分 目前的连续变形必须由重力驱动，同时又会因岩浆动力学而变得不稳定。我们不能排除侧翼运动演变成灾难性的崩溃，这意味着埃特纳火山的侧翼运动带来的危害要比以前想象的要大得多。在其他沿海和海洋岛屿火山中，侧面淹没的危险可能被低估了，在这些地方，淹没侧面的动力学是未知的。