Elevated CO2 emissions during magmatic-hydrothermal degassing at Awu Volcano, Sangihe Arc, Indonesia

Awu is a remote and little known active volcano of Indonesia located in the northern part of Molucca Sea. It is the northernmost active volcano of the Sangihe arc with 18 eruptions in less than 4 centuries, causing a cumulative death toll of 11,048. Two of these eruptions were classified with a Volcanic Explosivity Index (VEI) of 4. Since 2004, a lava dome has occupied the centre of Awu crater, channelling the fumarolic gas output along the crater wall. A combined Differential Optical Absorption Spectroscopy (DOAS) and Multi-component Gas Analyzer System (Multi-GAS) study highlight a relatively small SO2 flux (13 t/d) sustained by mixed magmatic–hydrothermal emissions made-up of 82 mol.% H2O, 15 mol.% CO2, 2.55 mol.% total S (ST) and 0.02 mol.% H2. The CO2 emission budget, as observed during a short observation period in 2015, corresponds to a daily contribution to the atmosphere of 2600 t/d, representing 1% of the global CO2 emission budget from volcanoes. The gas CO2/ST ratio of 3.7 to 7.9 is at the upper limit of the Indonesian gas range, which is ascribed to (i) some extent of S loss during hydrothermal processing, and perhaps (ii) a C-rich signature of the feeding magmatic gas phase. The source of this high CO2 signature and flux is yet to be fully understood; however, given the peculiar geodynamic context of the region, dominated by the arc-to-arc collision, this may result from either the prolonged heating of the slab and consequent production of carbon-rich fluids, or the recycling of crustal carbon

Volcano disaster risk management during crisis: implementation of risk communication in Indonesia

Abstract Volcano disaster risk management during a crisis requires continuous and intensive risk communication with the public. However, to have the desired public response during a crisis, it is necessary to improve the community’s understanding of volcanoes. Knowledge, experience, risk perception, communication, and drills shape good community responses. These require a bottom-up process of communication and involvement of the community in decision-making and engagement with the government. Thus, proper crisis management requires top-down and bottom-up communication and joint work between the scientists, decision-makers, and the community. The response from the community can be improved through community-based preparedness with a culturally sensitive approach that facilitates a strong relationship and participation of community members according to their customs. The Wajib Latih Penanggulangan Bencana (WLPB: Compulsory Disaster Management Training Program) and the SISTER VILLAGE Program in the Merapi Volcano community are good examples of community-based preparation in Indonesia. An effective volcano early warning protocol includes risks analysis, volcano monitoring, hazards analysis and forecasting, dissemination of alerts and warnings, and community response according to the warning. Alert levels can also be increased during the unrest, so actions are also associated with this and not just related to the impacts of an eruption. Therefore, the alert level alone is not helpful if it is not appropriately communicated with an action plan in place to improve community awareness. Moreover, personal communication between scientists and decision-makers and between scientists and the community is essential to instill self-responsibility and a sense of belonging. Personal communication describes the trust of community members or certain decision-makers to scientists to obtain more detailed explanations of volcanic activity. Such communication is already occurring in communities that have experienced a long history of eruptions, and/or continuous eruptions, such as at Merapi and Sinabung volcanoes. The disaster management system in Indonesia includes institutions that manage science and institutions responsible for social aspects, such as evacuations, refugee handling, rehabilitation, and reconstruction. The National Disaster Management Agency (NDMA, Badan Nasional Bencana, BNPB in Bahasa Indonesia) of Indonesia coordinates all disasters to integrate management of and facilitate communication between stakeholders. In addition to a well-established system, effective and good disaster management needs to be supported by policies related to public needs before, during, and after the disaster. After disasters, a review of previous strategies is also necessary to develop a better strategy and obtain a better result. Establishing SISTER VILLAGES is an excellent strategy to meet the needs during a crisis. However, this needs to be supported by regulations related to collecting data, the evacuation process and facilitation, and infrastructure, communication, and coordination. Here, we present good risk communication practices around Indonesia's volcanoes related to how people receive and understand early warning information and take action with the support of the government through capacity improvement and learning from experiences

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

First characterization of Gamkonora gas emission, North Maluku, East Indonesia

Gamkonora is an active volcano capable of intense manifestations that regularly forced thousands of inhabitants to flee their villages. The most extreme eruption, in 1673, was a VEI 5 event that induced pitch-dark environment over the region. Paradoxically, little is known about Gamkonora volcano and here we present the first gas measurement results obtained in September 2018 using a MultiGAS and a scanning DOAS. Results highlight a relatively small but magmatic gas with a CO2/ST of 3.5, in the range of high-temperature gas emissions from Indonesian volcanoes and H2O/SO2, CO2/SO2, H2S/SO2, and H2/SO2 ratios of 135, 5.6, 0.6, and 0.2, respectively. The daily gas emission budget corresponds to 129 t, 13 t, 3.4 t, 1.1 t, and 0.03 t for H2O, CO2, SO2, H2S, and H2, respectively. Bulk rock analyses indicate a basaltic andesite to andesite source beneath Gamkonora

First characterization of Gamkonora gas emission, North Maluku, East Indonesia

Gamkonora is an active volcano capable of intense manifestations that regularly forced thousands of inhabitants to flee their villages. The most extreme eruption, in 1673, was a VEI 5 event that induced pitch-dark environment over the region. Paradoxically, little is known about Gamkonora volcano and here we present the first gas measurement results obtained in September 2018 using a MultiGAS and a scanning DOAS. Results highlight a relatively small but magmatic gas with a CO2/S-T of 3.5, in the range of high-temperature gas emissions from Indonesian volcanoes and H2O/SO2, CO2/SO2, H2S/SO2, and H-2/SO2 ratios of 135, 5.6, 0.6, and 0.2, respectively. The daily gas emission budget corresponds to 129 t, 13 t, 3.4 t, 1.1 t, and 0.03 t for H2O, CO2, SO2, H2S, and H-2, respectively. Bulk rock analyses indicate a basaltic andesite to andesite source beneath Gamkonora

Structure of the acid hydrothermal system of Papandayan volcano, Indonesia, investigated by geophysical methods

Papandayan (2665 m asl) is an Indonesian stratovolcano located at 50 km from Bandung in west Java and characterized by an intense hydrothermal activity. An advanced alteration takes place where acid fluids interact with rocks, weakening the edifice, so that even minor explosive eruptions threaten the stability of its flanks. The purpose of the current study is to delineate the geometry of the acid hydrothermal plume using Electrical Resistivity Tomography (ERT). We used self-potential, pH measurements in water (in situ) and of soil samples, SO2 and CO2 soil concentration mappings to better understand the resistivity structure. Measurements have been performed inside the 1772 crater with a maximal depth of investigation of about 250 m for electrical resistivity tomography. At low pH, the mobility of H+ (or H3O+) ions represents a dominant contribution to the electrical conductivity leading to an unusually high conductivity of pore water. For Papandayan spring water, the theoretical electrical conductivity calculated for chemical composition and pH yield indeed exceptionally high values in the range 20- 25Sm(-1). The surface conductivity of the altered unconsolidated samples determined from a recent study (0.005Sm-1) with an extremely high bulk conductivity within the central part of the crater (similar to 2Sm(-1)). The main degassing zones in the crater, Kawah Emas, Manuk and Kawah Baru, are all connected by conduits to this common reservoir at a depth of 100 m. Because the location of this good conductor coincides with elevated ground temperature, main fumaroles, and with detectable SO2 degassing, we interpret it as an acid hydrothermal plume. Low pH impacts also the self-potential distribution: a clear correlation is observed between the pH values measured in soil samples and the self-potential. The main degassing area is associated with a negative anomaly of self-potential likely produced by the electro-kinetic effect due to upwelling fluid flow in acid conditions. It follows from our results that the assessment of the pH conditions is necessary for the interpretation of electrical resistivity structures and self-potential distribution on hydrothermal systems where acid conditions and acidity variations can be expected due to chemical reactions between volcanic gases and groundwater