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We use satellite imagery to investigate the shoreline changes associated with volcanic activity in 2018&ndash, 2019 at Anak Krakatau, Indonesia, spanning a major lateral collapse and period of regrowth through explosive activity. The shoreline changes have been analyzed and validated through the adaptation of an existing methodology based on Sentinel-2 multispectral imagery and developed on Google Earth Engine. This work tests the results of this method in a highly dynamic volcanic environment and validates them with manually digitized shorelines. The analysis shows that the size of the Anak Krakatau Island increased from 2.84 km2 to 3.19 km2 during 15 May 2018&ndash, 1 November 2019 despite the loss of area in the 22 December 2018 lateral collapse. The lateral collapse reduced the island area to ~1.5 km2 but this was followed by a rapid increase in area in the first two months of 2019, reaching up to 3.27 km2. This was followed by a period of little change as volcanic activity declined and then by a net decrease from May 2019 to 1 November 2019 that resulted from erosion on the SW side of the island. This history of post-collapse eruptive regrowth and coastal erosion derived from the shoreline changes illuminates the potential for satellite-based automated shoreline mapping to provide databases for monitoring remote island volcanoes.

Argoland is a piece of Gondwana that collided to the southeastern margin of Sundaland during Late Cretaceous to Early Tertiary. Recently, the existence and continuation of the missing Argoland beneath southern Java have become a hot topic related to geological exploration. The involvement of crustal assimilation of Argoland plays an important role in magma genesis. It controls eruption style, magma composition and also mineral deposit type. Although some studies have indicated the presence of micro continent beneath the southern part of West and East Java, they still could not explain its existence precisely and there are some difficulties to connect one to another. Petrological and geochemical studies of twenty active volcanoes from west to east were combined with tomographic study result to elucidate the problem and give better understanding of crust architecture and interior in Java. Our study shows that some of these magmas derived from Active Continental Margin represent those produced by partial melting of mantle wedge induced by natural fluid in subduction system due to interaction of continental and oceanic crusts. In agreement with geochemical data, high velocity zone from tomographic data are clearly shown in the southern part of Late Cretaceous to Early Tertiary Melange. If that is so, the extension of Argoland in East Java seems to continue to the Central and West Java. A new map of Argoland distribution, crust architecture and interior of Java is proposed.

Shoreline changes occur due to abrasion and accretion processes that are triggered due to intensive human activities in coastal areas. The shoreline in the Kendal region is dynamic, and shows mixed results from tidal and dominated by riverine activity. The Shoreline changes have different impacts, all of which may not be visible. Coastal dynamics in the Kendal region cause spatial-temporal shoreline changes. To observe these we need a long and continuous set of data. The purpose of this study is to determine changes in the shoreline in parts of the Kendal coastal district and to calculate the value of the changes. The data used were derived from TM data 1990, to OLI data 2017. To derive the shoreline from the satellite data, a band ratio of Red band to IR band was employed. The shorelines were digitized and saved along with the appropriate MM/DD/YYYY added to the attribute table. The Digital Shoreline Analysis System (DSAS) was used to compute rate-of-change statistics. The Digital Shoreline Analysis System (DSAS) is an extension of ArcGIS, developed by USGS. Using the extension, transects were laid every 100 m. Then, using NET SHORELINE MOVEMENT (NSM), LINEAR REGRESSION RATE (LRR) and END POINT RATE (EPR), the changes every 100 meters were analyzed and stored in a table. Subsequently, using the table, erosion, and accretion, were analyzed, and understood. The farthest accretion process was 1763.29 m and 792.14 m for the abrasion processes.

Sakurajima in Japan is one of the world’s most active volcanoes. This paper presents the results of a petrological study of the Showa Crater volcanic ash samples ejected from January 2011 to November 2012 from Sakurajima. The aim of this paper is to reconstruct the evolution in time of the conduit magma system, based on the compositions and physical properties of the studied volcanic ash. We analyzed the composition of interstitial glass and microcrystal of Black Volcanic Rock (BVR) and Black Vesicular Volcanic Rock (BVVR) in order to estimate the magma ascent rate. The results show that SiO2 content of interstitial glass and crystallinity of the BVR is generally higher than for BVVR. The different types of juvenile material likely resulted from cooling-induced crystallization and decompression-induced crystallization in the conduit. The conditions of magma transit within the conduit from 2011 to 2012 differ: in 2011, the decompression rate and magma ascent rate of BVR were higher than for BVVR, but, in 2012, the decompression rate and magma ascent rate between BVR and BVVR were similar. As such, monitoring the petrological features of dated eruptive materials could provide useful information for evaluating ongoing eruptive activity.

Many petrological studies of volcanic rocks have attempted to better predict future volcanic activity. In this study, we examined volcanic ash samples from Showa Crater in Sakurajima, Japan, which were erupted from January to October 2013. This study was used two types of juvenile material; black vesicular volcanic rock (BVVR) and black non-vesicular volcanic rock (BNVVR) to determine the variable of magmatic processes in the magma conduit during the 2013 eruption. We divided the duration into three periods such as January to April, April to July, and July to October based on the variable tendency of SiO2 contents and volume abundance of the interstitial glasses in BVVR and BNVVR. The estimated melt compositions demonstrate that the variability of SiO2 contents and volume abundance of microcrystal in the groundmass (BVVR and BNVVR) over time were caused by micro-crystallization processes. The estimated of water contents and vesicle volume shows the influence of degassing process in the rock forming. Also, the correlation of petrological features with the number of eruptions and eruptive volumes, exhibit the variable of magma supply into conduit in each period. Consequently, careful monitoring of the petrological features of erupted materials may provide useful constraints on future eruptive activity and thereby assist in the mitigation of volcanic hazards.