Abstract:We report the atmospheric Hg contamination in an artisanal and small-scale gold mining (ASGM) area in North Gorontalo, Indonesia. It is well known that atmospheric Hg contaminates the air, water, soil, and living organisms, including trees. In this study, we calculated total weight of heavy metals, especially Hg, and quantitatively measure the concentrations of heavy metals, especially Hg, in tree bark from an ASGM area. Tree bark can be used for the environmental assessment of atmospheric contamination because it attaches and absorbs heavy metals. Atmospheric Hg and other heavy metals, including Fe and Mn, and As were detected on the tree bark samples. The total weight of Hg, As, Fe, and Mn in the tree bark samples ranged from undetectable (ND) to 9.77, ND to 81.3, 124-4028, 37.0-1376 µg dry weight (DW), respectively per weight of sample. Based on quantitatively analysis micro-PIXE, the highest concentrations of all these metals were detected in the outer part of the bark. We conclude that tree bark can adsorb atmospheric contamination, which is then absorbed into the inner tissues.

We use satellite imagery to investigate the shoreline changes associated with volcanic activity in 2018–2019 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 2018–1 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.

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 SiO 2 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.

The extraordinary of geodiversity together with the ecological resources and profound cultural heritages provide a valuable basic of geotourism and geopark development. The purpose of this paper is to show the possibilities of geological interpretation, geotourism, and cultural heritages in the area of Gorontalo province that would become valuable basic to promote geopark. The collected data was carried out by field observation and literature review. The results of this study indicate that the Gorontalo has the potential of geopark and would serve as tourist destination in Sulawesi by applying the concept of Geotourism which accentuate natural side, by optimizing the management of destination attractions, facilities and services, and accessibilities.