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This paper discusses the relations between the impacts of volcanic eruptions at multiple-scales and the related-issues of disaster-risk reduction (DRR). The review is structured around local and global impacts of volcanic eruptions, which have not been widely discussed in the literature, in terms of DRR issues. We classify the impacts at local scale on four different geographical features: impacts on the drainage system, on the structural morphology, on the water bodies, and the impact on societies and the environment. It has been demonstrated that information on local impacts can be integrated into four phases of the DRR, i.e., monitoring, mapping, emergency, and recovery. In contrast, information on the global impacts (e.g., global disruption on climate and air traffic) only fits the first DRR phase. We have emphasized the fact that global impacts are almost forgotten in the DRR programs. For this review, we have extracted case studies from Indonesia, and compared them to those of other regions, because Indonesia is home to >130 volcanoes and experienced several latest volcanic eruptions with VEI > 5.

Indonesia is exposed to earthquakes, volcanic activities, and associated tsunamis. This is particularly the case for Lombok and Sumbawa Islands in West Nusa Tenggara, where evidence of tsunamis is frequently observed in its coastal sedimentary record. If the 1815 CE Tambora eruption on Sumbawa Island generated a tsunami with well-identified traces on the surrounding islands, little is known about the consequences of the 1257 CE tremendous eruption of Samalas on the neighboring islands, and especially about the possible tsunamis generated in reason of a paucity of research on coastal sedimentary records in this area. However, on Lombok Island, the eruption of the Samalas volcano produced significant volumes of pyroclastic flows that entered the sea in the North and East of the island. These phenomena must have produced a tsunami that left their traces, especially on Sumbawa Island, whose western coastline is only 14 km away from Lombok’s eastern shore. Therefore, the main goal of this study is to investigate, find evidence, and determine the age of marine-origin sediments along the shore of the Alas Strait, Indonesia. We collected and analyzed samples of coral and seashells from marine deposits identified along the west coast of Sumbawa, i.e., in Belang Island and abandoned fishponds in Kiantar Village, in order to identify the sources and the occurrence period of these deposits events. Based on the radiocarbon dating of coral and seashell samples, we concluded that none of the identified marine deposits along the western coast of Sumbawa could be related chronologically to the 1257 CE eruption of Samalas. However, possible tsunami deposits located in Belang Island and abandoned fishponds in Kiantar Village yielded 4th century CE, 9th century CE, and 17th century CE. We also conclude that past large earthquakes triggered these tsunamis since no known volcanic eruption occurred near the Alas Strait at that time that may have triggered a tsunami.

A detailed study had been conducted on the sediment of Mount Samalas’ volcanic eruption in 1257 AD. Using the framework of the reconstruction of the ancient eruption of Mount Samalas, the first step was to map and analyze the deposits of volcanic sediment. Secondly, we analyzed the effect of geomorphology and the distance function to the isopach thickness. The results show that a combination of methods allowed to provide a high resolution map of the distribution of the thickness of the volcanic deposits, both on the slope and in alluvial areas. Geo-electric survey results (both Vertical Electric Sound (VES) and 2D mapping) show consistent changes in the pattern of contrast resistivity layer interface, for all areas. The pattern changes in a row of the top layer, the high resistivity turned into the low. Furthermore, the second and third layer interface changes from low to the high resistivity. High resistivity on the top layer is interpreted as a layer of unconsolidated volcanic sediment. High resistivity values are range from 736 to 2000 Ohm.m on the top layer in the area of the slopes while in the area of alluvial, the resistivity values range from 20 to 958 Ohm.m. Generally, the volcanic deposits in the area of the slopes have a higher value of isopach (>17 m) than in areas of alluvial (