Submarine and Subaerial Morphological Changes Associated with the 2014 Eruption at Stromboli Island

Stromboli is an active insular volcano located in the Southern Tyrrhenian Sea and its recent volcanic activity is mostly confined within the Sciara del Fuoco (SdF, hereafter), a 2-km wide subaerial–submarine collapse scar, which morphologically dominates the NW flank of the edifice. In August-November 2014, an effusive eruption occurred along the steep SdF slope, with multiple lava flows reaching the sea. The integration of multisensor remote sensing data, including lidar, photogrammetric, bathymetric surveys coupled with SAR amplitude images collected before and after the 2014 eruption enabled to reconstruct the dynamics of the lava flows through the main morphological changes of the whole SdF slope. Well-defined and steep-sided ridges were created by lava flows during the early stages of the eruption, when effusion rates were high, favoring the penetration into the sea of lava flows as coherent bodies. Differently, fan-shaped features were emplaced during the declining stage of the eruption or in relation to lava overflows and associated gravel flows, suggesting the prevalence of volcaniclastic breccias with respect to coherent lava flows. The estimated volume of eruptive products emplaced on the SdF slope during the 2014 eruption, accounts for about 3.7 × 106 m3, 18% of which is in the submarine setting. This figure is different with respect to the previous 2007 eruption at Stromboli, when a large lava submarine delta formed. This discrepancy can be mainly related to the different elevation of the main vents feeding lava flows during the 2007 eruption (around 400 m) and the 2014 eruption (around 650 m). Besides slope accretion, instability processes were detected both in the subaerial and submarine SdF slope. Submarine slope failure mobilized at least 6 × 105 m3 of volcaniclastic material, representing the largest instability event detected since the 2007 lava delta emplacement.

The 2017 Nishinoshima eruption: combined analysis using Himawari-8 and multiple high-resolution satellite images

Nishinoshima volcano suddenly resumed eruptive activity in April 2017 after about 1.5 years of dormancy since its previous activity in 2013–2015. Nishinoshima is an uninhabited isolated island. We analyzed the eruption sequence and the eruptive process of the 2017 eruption (17 April–10 August: 116 days) by combining high-temporal-resolution images from Himawari-8 and high-spatial-resolution images from the ALOS-2, Landsat-8, and Pleiades satellites. We used these data to discuss how temporal variations in the lava effusion rate affected the flow formations and topographical features of the effused lava. The total effused volume was estimated to be 1.6 × 107 m3, and the average effusion rate was 1.5 × 105 m3/day (1.7 m3/s). Based on variations in the thermal anomalies in the 1.6-μm band of Himawari-8, which roughly coincided with that of the lava effusion rate estimated by ALOS-2, the activity was segmented into five stages. In Stage 1 (17–30 April: 14 days), the lava effusion rate was the highest, and lava flowed to the west and southwest. Stage 2 (1 May–5 June: 36 days) showed a uniform decrease in flow, and lava flowed to the southwest and formed the southwestern lava delta. During Stage 3 (6–15 June: 10 days), the lava effusion rate increased in a pulsed manner, the flow direction changed from southwestward to westward, and a narrow lava flow effused from the southern slope of the cone. In Stage 4 (16 June–31 July: 46 days), the lava effusion rate decreased and lava flowed westward through lava tubes, enlarging the western lava delta. Around the end of July, lava effusion mostly stopped. Finally, in Stage 5 (1–10 August: 10 days), explosive eruptions occurred sporadically. The variation in lava effusion rate seemed to play an important role in forming different flow patterns of lava on Nishinoshima. In Stages 1 and 3, lava flowed in multiple directions, while in Stages 2 and 4, it flowed in single direction, probably because the effusion rate was lower. A pulsed increase in the lava effusion rate during Stage 3 caused new breaks and disturbances of the lava passages near the vents, which resulted in changes in flow directions. Differences in the size of lava lobes between the southwestern and western deltas are also considered to result from differences in the lava effusion rate.

Bárcena Volcano, 1952: a 60-year report on the repopulation of San Benedicto Island, Mexico, with a review of the ecological impacts of disastrous events

Long-term ecological studies are desirable, but rare. I here present data from a 60-year study on the repopulation of San Benedicto Island following a volcano eruption in 1952. Bárcena Volcano appeared on 1 August 1952 on San Benedicto Island, Revillagigedo Islands, Mexico. Within 20 min, the entire island was engulfed in a cloud of ash and pumice, which covered all the plants, killed an estimated 20 000 sea birds within hours and caused the subsequent extinction of an endemic race of rock wren (Salpinctes obsoleta exsul). The results of studies on revegetation and repopulation of the island for the first 10 years after the volcanic eruption were summarised by Brattstrom in 1963. This report extends the studies to 2012. The distribution of the land crab (Aegecarcinus planatus) has increased on the island. By 1971 the crab occurred only over the northern one-eighth of the island, but by 1978 it could be found on one-third of the island. No studies on its distribution have been made since then. Total sea bird populations steadily increased up to 1971 and then rapidly declined, though these changes in numbers are largely due to a fluctuation in the populations of the masked booby (Sula dactylatra). The changes in the booby population may have been due to reproductive and feeding success or to immigration and emigration. The decline in the shearwater (Puffinus ssp.) populations are largely due to erosion and destruction of their burrows; their numbers did not increase until 2000. The formation of a large lava delta created a new habitat, which permitted the establishment of a species of sea bird new to the island, the red-footed booby (Sula sula). Numerous non-resident waifs or stray birds have been observed on the island but most have not become established. The exception is the Laysan albatross (Phoebastria immutabilis), breeding at present in low (3–712) numbers. The original flora consisted of 10 species. The volcano caused four species to become extinct, two re-established themselves, and two species new to the island arrived. There have been marked erosional changes, and the accidental introduction of exotic plants may dramatically alter the vegetation of the island.