Eruptions In Indonesia Research Articles

A 5000-year record of multiple highly explosive mafic eruptions from Gunung Agung (Bali, Indonesia): implications for eruption frequency and volcanic hazards

The 1963 AD eruption of Agung volcano was one of the most significant twentieth century eruptions in Indonesia, both in terms of its explosivity (volcanic explosivity index (VEI) of 4+) and its short-term climatic impact as a result of around 6.5 Mt SO2 emitted during the eruption. Because Agung has a significant potential to generate more sulphur-rich explosive eruptions in the future and in the wake of reported geophysical unrest between 2007 and 2011, we investigated the Late Holocene tephrostratigraphic record of this volcano using stratigraphic logging, and geochemical and geochronological analyses. We show that Agung has an average eruptive frequency of one VEI ≥2–3 eruptions per century. The Late Holocene eruptive record is dominated by basaltic andesitic eruptions generating tephra fall and pyroclastic density currents. About 25 % of eruptions are of similar or larger magnitude than the 1963 AD event, and this includes the previous eruption of 1843 AD (estimated VEI 5, contrary to previous estimations of VEI 2). The latter represents one of the chemically most evolved products (andesite) erupted at Agung. In the Late Holocene, periods of more intense explosive activity alternated with periods of background eruptive rates similar to those at other subduction zone volcanoes. All eruptive products at Agung show a texturally complex mineral assemblage, dominated by plagioclase, clinopyroxene, orthopyroxene and olivine, suggesting recurring open-system processes of magmatic differentiation. We propose that erupted magmas are the result of repeated intrusions of basaltic magmas into basaltic andesitic to andesitic reservoirs producing a hybrid of bulk basaltic andesitic composition with limited compositional variations.

The adaptive governance of natural disaster systems: Insights from the 2010 mount Merapi eruption in Indonesia

An adaptive governance system strives to enhance the capacity of institutions to better coordinate relief operations, public awareness and risk reduction policy in case of natural or man-made disasters, by promoting learning from experience. The contribution of this article is twofold: (1) to establish an assessment framework for the adaptive capacity of a system in the field of disasters, and (2) to explore the governance system of Mt. Merapi volcano, Indonesia. We chose the Merapi volcano in the wake of the large 2010 eruption, the largest event over the past 140 years. We develop and apply an assessment framework for the adaptive capacity of a system with the following six key parameters: (1) system description, (2) technology, (3) infrastructure, (4) institutions, (5) information and skills, and (6) economic and financial resources. The methodology consists of a qualitative analysis, using a text analysis. The data have been collected from a field survey, which was conducted after the 2010 volcanic eruption and rain-triggered lahars on Mt. Merapi in central Java. We underline a number of challenges, such as apparent lack of appropriate infrastructures, complex interactions across institutions, dependence on funds from external parties, and limited quantitative documentation on both human and material loss, which may weaken the adaptive capacity of the system. More efforts are therefore needed in order to improve the adaptive capacity and, thus, the adaptive governance at Mt. Merapi. This study represents a significant step toward enhancing our understanding of the adaptive governance approach in developing countries.

Lusi mud eruption triggered by geometric focusing of seismic waves

The Lusi mud eruption in Indonesia has been ongoing since 2006. Numerical simulations show that a parabolic-shaped layer in the rock surrounding the site of the Lusi eruption could have amplified and focussed incoming seismic energy from an earthquake, which then triggered the mud eruption.

The warias of Indonesia in disaster risk reduction: the case of the 2010 Mt Merapi eruption in Indonesia

This field note draws upon the concepts of vulnerability, marginalisation, and capacity of lesbian, gay, bisexual, and transgender (LGBT) people to face natural hazards. As a case study, this paper highlights the response of warias, members of the LGBT community in Indonesia, during the 2010 Mt Merapi eruption. Through key informant interviews and observation of actual relief operations led by warias in several evacuation sites in Yogyakarta and Central Java, the paper highlights that warias contributed to disaster risk reduction (DRR) even though they are marginalised and discriminated in the country because of prevailing religious and societal attitudes. The paper argues that their needs and capacities should be acknowledged in DRR policies and practice.

Sulphide magma as a source of metals in arc-related magmatic hydrothermal ore fluids

As magma ascends in subduction zones, decreasing pressure and temperature cause it to separate into two or more phases in a process known as exsolution. Hydrothermal ore fluids and metal-rich sulphide melts may be products of this exsolution. Conventionally, the ore fluids are thought to acquire their metal content directly from the parent magma. However, it is probable that the ore fluids and sulphide melts interact after exsolution, and therefore possible that the sulphide melts are an important source of metals for the ore fluids. Here we use petrographic analyses of erupted sulphide melts and compositional analyses of volcanic gases emitted immediately after an eruption at Merapi Volcano, Indonesia, to show that magmatic hydrothermal fluids can derive their metals from dissolution of sulphide melts. We find that the volcanic gases exhibit metal ratios that are comparable to those in the erupted sulphide melts. Furthermore, we show that gases sampled immediately after the eruption have metal concentrations that are orders of magnitude higher than those of gases emitted during periods of quiescence. We propose that the metal content of ores forming in volcanic arc environments is established by exsolution accompanying injections of primitive magma immediately before explosive eruptions. The metal content of ore deposits formed during subduction-zone volcanism was thought to be established when the ore fluid separates from the parent magma. Analyses of metal concentrations in erupted melts and the volcanic gases emitted after an eruption in Indonesia reveal that metals can be added to the ore fluid later, during mixing with separated melts.

Seasonal variation in long-range transported dust to a subtropical islet offshore northern Taiwan: Chemical composition and Sr isotopic evidence in rainwater

We investigated chemical and Sr isotopic composition of monthly rainwater collected on Peng-Chia-Yu (PCY) in northern Taiwan. Rainwater 87Sr/ 86Sr ratios, Na/Cl, Ca/Cl, Sr/Cl, Sr/Ca, NH 4/Cl, NO 3/Cl, SO 4/Cl and Na/Sr, showed clear seasonal cycles, reflecting mixture of loess carbonates (high Ca/Sr and more radiogenic 87Sr/ 86Sr) and seawater (low Ca/Sr and intermediate 87Sr/ 86Sr). Model results showed that the former source contributes up to 45% during the winter monsoon period, but seawater is the dominant Sr source in rainwater (>50%) at other times. Two anomalously low 87Sr/ 86Sr values occurred in July and August 1998, coinciding with the Merapi eruption in Indonesia. Air-mass backward trajectories and the geochemical and isotopic compositions in rainwater and Merapi lava (i.e. Ca/Sr = 100 and 87Sr/ 86Sr = 0.705400) suggested that the Merapi eruption delivered ash across the western equatorial Pacific to PCY. Aerosols leaching experiments were conducted to examine the impact of the 1998 eruption, demonstrating that only a minor terrestrial signature can be extracted by distilled water, implying rapid dispatch of volcanic gases or high-efficiency dissolution of ash related substance in acidic rains.

Cold decade (AD 1810–1819) caused by Tambora (1815) and another (1809) stratospheric volcanic eruption

Climate records indicate that the decade of AD 1810–1819 including “the year without a summer” (1816) is probably the coldest during the past 500 years or longer, and the cause of the climatic extreme has been attributed primarily to the 1815 cataclysmic Tambora eruption in Indonesia. But the cold temperatures in the early part of the decade and the timing of the Tambora eruption call into question the real climatic impact of volcanic eruptions. Here we present new evidence, based on sulfur isotope anomaly (Δ33S), a unique indicator of volcanic sulfuric acid produced in the stratosphere and preserved in polar snow, and on the precise timing of the volcanic deposition in both polar regions, that another large eruption in 1809 of a volcano is also stratospheric and occurred in the tropics. The Tambora eruption and the undocumented 1809 eruption are together responsible for the unusually cold decade.

Modelling eruption cycles and decay of mud volcanoes

Recent debates about the eruptive behavior of mud volcanoes and their activation mechanisms have been driven particularly by the LUSI eruption in Indonesia that resulted in huge commercial and cultural damages. Numerical modeling of mud volcanoes, of which few exist, can provide insight into eruptive behavior and contribute to hazard evaluation. In this paper, we present a simple model to describe fluid escape from an underground reservoir through a conduit, extruded as a mud volcano at the surface. The governing equations result in oscillatory behavior, and we study the influence of changes in rheological properties of surrounding rock and fluid characteristics of the mud on extrusion dynamics. We focus on understanding long-term eruption behavior, flow cycles, and decay factors. Model results can be used to estimate the discharge rates and extruded volume from assumptions on the mud reservoir and conduit, or conversely, the reservoir or conduit properties from discharge rates.

Tree-ring based summer temperature reconstruction for the source region of the Yangtze River on the Tibetan Plateau

Understanding of past climatic variability over the Tibetan Plateau is still limited because of the lack of long-term climatic records. Here we reconstruct the mean summer (June–August) minimum temperature for the past 379 years based on tree-ring data in the source region of the Yangtze River. This reconstruction successfully captures recent abrupt climatic changes and agrees in general with other temperature reconstructions for the Tibetan Plateau on a decadal timescale. The cold and warm periods coincide with documented glacier advances and retreats on the east and southeast Tibetan Plateau. The interval 1816–22 is among the coldest periods in the reconstruction and may be related to the influence of the Tambora eruption in Indonesia in 1815. Comparisons with other paleoclimatic proxies imply a high degree of confidence for our reconstruction and its indicative power for a large-scale climate variability on the Tibetan Plateau.

Solar radiation climate change over southern Africa and an assessment of the radiative impact of volcanic eruptions

Spatial and temporal variability in global, diffuse, and horizontal direct irradiance and sunshine duration has been evaluated at eight stations in South Africa and two stations in Namibia where the time series range between 21 and 41 years. Global and direct irradiance and sunshine duration decrease from northwest to southeast; diffuse irradiance increases toward the east. Annually averaged global irradiance Ga decreased between 1.3% (2.8 W m−2) and 1.7% (4.4 W m−2) per decade at Bloemfontein, Cape Town, Durban, Pretoria, and Upington. Annually averaged diffuse irradiance Da decreased 5.2% (3.0 W m−2) per decade at Grootfontein and 4.2% (3.1 W m−2) per decade at Port Elizabeth. Annual direct irradiance Ba decreased 2.1% (3.5 W m−2) per decade at Cape Town and 2.8% (5.7 W m−2) per decade at Alexander Bay. A simultaneous decrease in annually averaged daily sunshine duration Sa may have contributed to the decrease in Ba at Alexander Bay and the decrease in Ga at Pretoria. Increases in aerosols may have contributed to the observed decrease in Ga at Cape Town and Durban, and the decrease in Da at Grootfontein may be due to a decrease in aerosols. On average, variability in Sa explains 89.0%, 50.4%, and 89.5% of the variance in Ga, Da, and Ba respectively. The radiative response to changes in sunshine duration is greater for direct irradiance than for global and diffuse. In the 2 years following the 1963 Mount Agung eruption in Indonesia, changes in global irradiance over southern Africa were small and inconsistent. At eight stations, diffuse irradiance increased 21.9% (13.3 W m−2) on average and direct irradiance decreased 8.7% (15.5 W m−2). After the 1982 El Chichón eruption in Mexico, global irradiance increased at two stations and decreased at seven stations. Eight stations witnessed an increase in diffuse irradiance averaging 7.2% (4.0 W m−2) and a decrease in direct irradiance of 5.0% (9.0 W m−2). The contribution of changes in cloud cover to the observed changes in irradiances appears to be small. Following the 1991 Mount Pinatubo eruption in the Philippines, diffuse irradiance increased an average of 18.8% (10.0 W m−2) at three stations and direct irradiance decreased by 7.2% (13.0 W m−2). Copyright © 2005 Royal Meteorological Society

Volcanic hazard mapping in Indonesia

Indonesia is a wide archipelago where 129 active volcanoes are located. It means that about 13% of active volcanoes all over the world are located in the Indonesian archipelago. The volcanoes are located along the 7,000 km tectonic belt through Sumatera, Java, Nusa Tenggara, North Sulawesi, North Maluku, up to South Maluku. About 10% of the Indonesian population live in the dangerous volcanic areas. In the last 300 years, some 175 thousands people were killed by volcanic eruptions in Indonesia. The volcanic hazard mitigation is carried out technically by the Volcanological Survey ofIndonesia which is unified in the National Coordination Agency for Disaster Management. One of the programs carried out is Volcanic Hazard Mapping. The Volcanic Hazard Map is one identifying the degree of volcanic hazard in an area. It is used as a guidance for evacuation purposes when the volcano is in eruption or in increasing activity. Determination of volcanic hazard zones can be divided into three levels of hazard zone where from the highest to the lowest are hazard zone III, hazard zone II, and hazard zone I, respectively. The Hazard Zone III is a zone which is very frequently affected by pyroclastic flow, lava flow, glowing rock fall, and poisonous gas, such as Mt. Semeru (East Java) and Mt. Merapi (Central Java). The Hazard Zone II is a zone which is potentially affected by pyroclastic flow, lava flow, ejected glowing rock, heavy ash fall, hot mud falls, lahar flow and poisonous gas. The Hazard Zone I is a zone which is potentially affected by lahar or flood and it still possible to be affected by an expanded pyroclastic flow and lava flow. The three levels of the hazard zonation is applicable on the very active volcanoes, which erupts very frequently. This is supported by a lot of data about them and consequently, the character ofthe volcanoes can mostly be recognized. In fact, many other active volcanoes have very limited supporting data. In case of development of volcanic resources or that of developing an area especially on volcanoes area which have poor reference data, a detailed study of volcanic hazard assessment on the area is required to be done in the fe asibility study. The Volcanic Hazard Map can be utilized firstly as a guide for evacuating people when the volcano is erupting, secondly as one of the main references for Regional Planning, and thirdly, for early warning system.

Mount Tambora in 1815: A Volcanic Eruption in Indonesia and Its Aftermath

The volcano Tambora on the Indonesian island of Sumbawa made history in April 1815. Its eruption at that time was a catastrophe without equal in recorded history. Large parts of the Indonesian archipelago were plunged into darkness for three days as a consequence of the vast quantities of ash released by the eruption. The sounds of explosions accompanying the eruption were audible as far away as Sumatra, and in many places were mistaken for cannon reports. In Makasar and Jogyakarta troops even prepared to march into battle,2 and it only became clear from the ash showers pouring down a few days later that what had taken place was not a military action but a volcanic eruption. The consequences of

Pyroclastic flows of the 1883 Krakatau eruption

The nature of the submarine deposits produced by the 1883 Krakatau eruption in Indonesia has remained controversial for more than a century. Knowledge of their character, however, is critical to understanding the origin of the devastating tsunamis generated during the event, which claimed about 36,000 lives. Results of a 1990 marine geological investigation reported here demonstrate that the deposits are largely of pyroclastic flow origin. Pyroclastic flows are partially fluidized mixtures of particles and gases that travel up to 150 m/s and have internal temperatures as high as 600°C. They are denser than the atmosphere but are likely to be comparable to seawater in density. What happens when such a flow encounters the sea along the coast of an active volcano has been the subject of much speculation [Cas and Wright, 1987] but little research [Sparks et al., 1980a, 1980b]. One well‐known effect is the generation of tsunamis [Kienle et al., 1987] and indeed, 20% of all volcanogenic tsunamis have been attributed to the entrance of pyroclastic flows into the sea [Latter, 1981]. The most devastating of these occurred during the 1883 eruption of Krakatau volcano.

Monitoring volcanic eruptions in Indonesia using weather satellite data: The Colo eruption of July 28, 1983

The monitoring of Colo Volcano activity, during its eruption episode of July to September 1983, was made difficult by the fact that the volcano is located on a small island which became engulfed by ash and nuees ardentes. The radiometer installed onboard the NOAA-7 satellite made a series of observations of the events accompanied by the emission of smoke and ashes. The July 28, 1983 data which show a well-defined plume extending from Sulawesi to Kalimantan have been digitally analyzed. The results of the analysis show that important and timely information regarding volcanic activity can be extracted from the multispectral satellite data. Such information can be a useful input in monitoring and early warning operations.