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Analyzing the geomorphometric traces of volcanic eruptions by comparing pre- and post-eruption maps and images of volcanic edifices can quantitatively indicate drastic changes in topography enlightening the effects of volcanic flank collapses. Volcanic edifices are inherently prone to experience flank collapses and related large landslides at some point of their evolution, which significantly change the volcanic landscape and totally destroy everything in their paths. If the flank collapses occurred on volcanic edifices in islands, they are also adequate to cause tsunamis with larger devastating effects. Thus, recognizing the imprints of flank collapses and their effects on volcanic edifices has critical importance. Comparison of pre- and post-eruption elevation, slope, aspect, and hypsometry analyses of the regular cone-shaped pre-eruption volcanic edifice as in the case of May 18, 1980 eruption of Mount St. Helens in Washington provides an excellent opportunity to understand the influence of such a rapid catastrophic event on landscape evolution. The volcanic flank collapse during the eruption particularly affected the upper 1500 m. The collapsed part increased the percentage of region between 1500 and 2150 m, particularly accumulated around ~ 1950 m, and created a plateau morphology because of landsliding and debris avalanche. The maximum and average maximum slope values of the edifice significantly increased in the upper part of this altitude due to flank collapse-related scar development. Post-eruption redistributions of slope values and aspect directions have also changed obviously, and represent the signatures of an amphitheater (horseshoe/C-) shaped scarp and plateau morphology developments particularly for the highest (40° <) and lowest (0–10°) slope ranges, respectively. On the other hand, the comparison of pre- and post-eruption hypsometries of the volcanic edifice represents an increase against the decreased relief of the volcanic edifice as a result of the flank collapse and landsliding, which created a large plateau on the northern sector, affected the elevation-area relation of the volcanic edifice in a different way. The results represent how such a destructive event can be a rejuvenating process on the topography as in the case of Mount St. Helens by increasing slope and hypsometry. [ABSTRACT FROM AUTHOR]

On 22 March 2014, a massive, catastrophic landslide occurred near Oso, Washington, USA, sweeping more than 1 km across the adjacent valley flats and killing 43 people. For the following 5 weeks, hundreds of workers engaged in an exhaustive search, rescue, and recovery effort directly in the landslide runout path. These workers could not avoid the risks posed by additional large-scale slope collapses. In an effort to ensure worker safety, multiple agencies cooperated to swiftly deploy a monitoring and alerting system consisting of sensors, automated data processing and web-based display, along with defined communication protocols and clear calls to action for emergency management and search personnel. Guided by the principle that an accelerating landslide poses a greater threat than a steadily moving or stationary mass, the system was designed to detect ground motion and vibration using complementary monitoring techniques. Near real-time information was provided by continuous GPS, seismometers/geophones, and extensometers. This information was augmented by repeat-assessment techniques such as terrestrial and aerial laser scanning and time-lapse photography. Fortunately, no major additional landsliding occurred. However, we did detect small headscarp failures as well as slow movement of the remaining landslide mass with the monitoring system. This was an exceptional response situation and the lessons learned are applicable to other landslide disaster crises. They underscore the need for cogent landslide expertise and ready-to-deploy monitoring equipment, the value of using redundant monitoring techniques with distinct goals, the benefit of clearly defined communication protocols, and the importance of continued research into forecasting landslide behavior to allow timely warning. [ABSTRACT FROM AUTHOR]