Soputan Volcano, Indonesia: Petrological Systematics of Volatiles and Magmas and their Bearing on Explosive Eruptions of a Basalt Volcano

Soputan volcano is one of the few basaltic volcanoes among 127 active volcanoes in Indonesia. It is part of the Sempu-Soputan volcanic complex located south of Tondano Caldera, North Sulawesi and commonly produces both explosive eruptions with VEI 2-3 and effusive lava dome and flow eruptions. Over the last two decades, Soputan had thirteen eruptions, the most recent in 2016. Most eruptions started explosively, followed by dome growth and in some cases pyroclastic flows. Our study focuses on understanding the magmatic system of Soputan and what processes are responsible for its highly explosive eruptions, which are typically uncommon for a basaltic magma composition. Our study includes tephra samples predating the 1911 eruptions, lava flow samples from the 2015 eruption, and ash from a 2015 fallout deposit. Our whole rock major and trace element composition are virtually identical to lava flow and select pyroclastic deposit compositions of Kushendratno et al. (2012) for the 1911-1912 and 1991-2007 eruptions. Bulk rocks contain 49 to 51 wt.% SiO2, whereas 2015 ash samples are slightly more silicic with 53 wt.% SiO2, consistent with segregation of groundmass from phenocrysts in the eruption cloud. Mantle normalized incompatible trace elements indicate strongly depleted HFSE (High Field Strength Elements) and REE (Rare Earth Elements) signatures but with spikes at Pb and Sr and mild enrichment of Rb and Ba. In comparison of data of this study with what was reported by Kushendratno et al. (2012), Fo68-79 olivine-hosted melt inclusions range from basaltic (48-52 wt.% SiO2) to basaltic andesite (54-55 wt.%) as compared to 54 - 65 wt.% SiO2 glass in Fo68-74 olivines. The compositional range of melt inclusions is consistent with 50% fractionation of multiple minerals including observed phenocrysts of olivine, plagioclase, pyroxene and oxides. Compositional trends with an inflection point likely reflect a change in the crystallizing assemblage, where early crystallization includes clinopyroxene and plagioclase, while later crystallization is dominated by plagioclase. New volatile concentration data from melt inclusions (S max. 0.35 wt.%, Cl max. 0.17%, H2O max. 5.2 wt.% from FTIR analyses) are higher than previously reported from younger samples (S max. ~0.07 wt.%, Cl max. 0.2%, H2O max. ~1 wt.%). H2O is relatively constant (~1-4 wt.%) for individual tephra samples (data by FTIR and water by difference method). Our inclusion data suggest that more volatile-rich magmas exist at depth and this is consistent with a model whereby recharge of deep, volatile-rich magmas into a more degassed and crystal-rich magma initiates a new, highly explosive eruption

Implementation of Robotic Process Automation in Public Sector Goods and Services e-Procurement Audit

Indonesia has adopted e-Procurement through an electronic procurement system (SPSE) implemented by the Electronic Procurement Service to improve transparency and efficiency in the procurement of goods and services (LPSE). Although the data/information presented in the LPSE is easily accessible, using the data in the LPSE for supervisory or audit functions is still not optimal, despite the fact that procurement of goods and services is the area with the highest corruption cases in Indonesia. The large amount of data in LPSE makes the audit process difficult because there is too much data to consider, especially if the audit process is still manual. As a result, auditors must use information technology to aid audit activities, also known as Computer Assisted Audit Techniques (TABK). In the field of public procurement auditing, the methodology for extracting large amounts of information is also unknown. Robotic Process Automation (RPA), which is thought to have great potential to facilitate audit work, is one of the information technologies that can help with the process of extracting large amounts of data. The author attempts to investigate how the implementation of RPA in the audit of the procurement of goods and services in the public sector that were analyzed descriptively in this study. The study's findings show that process automation can be done well and produce data that can be used in audits

Writing Short Stories Using Twitter as a Media for Student’s Writing Skills

The purpose of this research is to find out the improvement of students writing short story about their most memorable experiences using Twitter as their writing media. Samples was students of class IX SMP N 3 Tangerang with a total of 30 students. According to Hadi, M, S. (2019), to solve problems and improve the quality of learning, researchers use Classroom Action Research to reduce misconceptions. Researchers conducted 1 Pre-Test session and 2 Post-Test sessions. And researchers collected data in this study by using Qualitative data from the description of students writing story using Twitter. From the results of the study showed that by using social media Twitter as written media students can improve students’ ability to write English and increase students' experience in conveying their expressions with written stories. From the results of the Pre-Test session, there were only 2 students who scored between 60 to 64. And 28 students get grades below 60. While during the Post-test 1 session, there was an increase in students with a total of 2 students getting grades above 70. Then during the Post-Test 2 session, the increase in students improved with the achievement of student grades the highest is 80 and the lowest is 65

Geochemical and Thermodinamic Modeling of Segara Anak Lake and the 2009 Eruption of Rinjani Volcano, Lombok, Indonesia

DOI: 10.17014/ijog.v5i4.106Rinjani is the second highest volcano in Indonesia with an elevation of 3726 m above sea level. The steep and highest cone of Rinjani consists mainly of loose pyroclastic ejecta and contains a crater with a few solfataras. The West of this cone is Segara Anak caldera. The western side of the caldera is occupied by a 230 m deep lake, covering an area of 11 km² and its volume was (before the 2009 eruption) estimated 1.02 km3. This is probably the largest hot volcanic lake in the world.The lake water is neutral (pH: 7-8) and its chemistry dominated by chlorides and sulfates with a relatively high TDS (Total Dissolved Solids: 2640 mg/l). This unusual TDS as well as the lake surface temperatures (20 - 22°C) well above ambient temperatures (14 - 15°C) for this altitude, reflect a strong input of hydrothermal fluids. Numerous hot springs are located along the shore at the foot of Barujari volcanic cone. Bathymetric profiles show also several areas with columns of gas bubbles escaping from the lake floor indicating a significant discharge of CO gas into the lake. The mass and energy balance model of Rinjani Crater Lake produce total heat lost value on the average of 1700 MW. Most of the heating periods of the lake occurred when the heat released by the surface of the lake to the atmosphere was lower than the heat supplied from the hydrothermal system. Peaks of heat losses correspond to period of strong winds. Crater lake monitoring can provide a basic information about deep magmatic activity and surface processes that occur in the volcano. The monitoring also contributes to predict the next eruption in order to improve mitigation of volcanic eruption. Precursory signals of the May 2009 eruption can be seen from significant changes in the temperature and chemistry of some of the hot springs, the increase of Fe concentrations in spring #54, chemical plume of low pH and dissolved oxygen, acidification of Segara Anak Lake, and increasing of lake surface temperatures. The new lava flow from May - August 2009 eruption covers an area of 650,000 m2. The shoreline was significantly modified by the entry of lava into Segara Anak Lake. The area of the lake is reduced by 460,000 m2

Prospect of Bentonite Mining in Indonesia

Hal. 27-3

Insights into the recurrent energetic eruptions that drive Awu, among the deadliest volcanoes on Earth

International audienceAbstract. The little-known Awu volcano (Sangihe Islands, Indonesia) is among the deadliest, with a cumulative death toll of 11 048. In less than 4 centuries, 18 eruptions were recorded, including two VEI 4 and three VEI 3 eruptions with worldwide impacts. The regional geodynamic setting is controlled by a divergent-double-subduction collision and an arc–arc collision. In that context, the slab stalls in the mantle, undergoes an increase in temperature, and becomes prone to melting, a process that sustained the magmatic supply. Awu also has the particularity of hosting alternatively and simultaneously a lava dome and a crater lake throughout its activity. The lava dome passively erupted through the crater lake and induced strong water evaporation from the crater. A conduit plug associated with this dome emplacement subsequently channeled the gas emission to the crater wall. However, with the lava dome cooling, the high annual rainfall eventually reconstituted the crater lake and created a hazardous situation on Awu. Indeed with a new magma injection, rapid pressure buildup may pulverize the conduit plug and the lava dome, allowing lake water injection and subsequent explosive water–magma interaction. The past vigorous eruptions are likely induced by these phenomena, possible scenarios for future events

Insights into the recurrent energetic eruptions that drive Awu, among the deadliest volcanoes on Earth

The little-known Awu volcano (Sangihe Islands, Indonesia) is among the deadliest, with a cumulative death toll of 11 048. In less than 4 centuries, 18 eruptions were recorded, including two VEI 4 and three VEI 3 eruptions with worldwide impacts. The regional geodynamic setting is controlled by a divergent-double-subduction collision and an arc-arc collision. In that context, the slab stalls in the mantle, undergoes an increase in temperature, and becomes prone to melting, a process that sustained the magmatic supply. Awu also has the particularity of hosting alternatively and simultaneously a lava dome and a crater lake throughout its activity. The lava dome passively erupted through the crater lake and induced strong water evaporation from the crater. A conduit plug associated with this dome emplacement subsequently channeled the gas emission to the crater wall. However, with the lava dome cooling, the high annual rainfall eventually reconstituted the crater lake and created a hazardous situation on Awu. Indeed with a new magma injection, rapid pressure buildup may pulverize the conduit plug and the lava dome, allowing lake water injection and subsequent explosive water-magma interaction. The past vigorous eruptions are likely induced by these phenomena, possible scenarios for future events

First gas and thermal measurements at the frequently erupting Gamalama volcano (Indonesia) reveal a hydrothermally dominated magmatic system

The first gas and thermal measurements at the summit of the Gamalama volcano indicate that the system is dominated by hydrothermal processes. This is highlighted by the prevalence of H2S over SO2 (H2S/SO2 = 2–8), a high CO2/SO2 ratio (76–201), and a low heat transfer (3.0 MW) to the surface. A relative variation in gas composition is observed along the degassing fracture zone, possibly due to partial S scrubbing. Despite this surface hydrothermal signature, the system exhibits high gas equilibrium temperatures (425–480 °C), indicating that fluids are not exclusively derived from a boiling hydrothermal aquifer, but also sourced by cooling and crystallizing basaltic magma at deep that continues to inject magmatic fluids into the system. This hydrothermally dominated activity on Gamalama possibly persisted over the last two decades, during which a high number of eruptive events were witnessed. The period coincides with the opening of large fractures at the summit that subsequently shifted the volcanic activity from the crater center to the peripheral fractures zones. These fractures that possibly developed in response to the regional geodynamics, have weakened the hydrothermal seal, allowing the pressure developed by the hydrothermal-magmatic system and promoted by the high annual rainfall, to rapidly exceeds the tensile strength of the seal leading to the numerous phreatic eruptions