Volcanic Hazard Map Research Articles

Re-assessing volcanic hazard maps for improving volcanic risk communication: application to Stromboli Island, Italy

Please click here to download the map associated with this article. Hazard and risk maps are tools for both mitigating against risk and informing and preparing the general public. Recent studies have highlighted that volcanic hazard and risk maps used during emergencies can be difficult to interpret. Our research focuses on evaluating and improving the efficacy of currently available maps of Stromboli volcano on Stromboli island (Italy) for the communication of volcanic hazard and risk information. Stromboli is an active volcano characterised by persistent explosive activity, sporadic lava effusions and landslides on the volcanos northwestern flank, which sometimes generates tsunamis, most recently in 2002. This study used semi-structured interviews conducted with local legislators, administrators and ‘enforcers’ to understand their perceptions of available risk information; to evaluate the respondents mental spatial maps; and to determine the most important components in encouraging risk-reducing behaviour in a hazardous situation. Respondents were asked to evaluate a contour map, an aerial photograph, a digital elevation model (DEM) and an innovative 3D tsunami risk map. These results enabled the development of different volcanic risk maps for use by ‘experts’ and ‘tourists’ using a contour map and a DEM (Scale 1:12.500). A 3D map focused on the tsunami risk (Scale 1:6.500) area was also produced.

Mitigation Systems by Hazard Maps, Mitigation Plans, and Risk Analyses Regarding Volcanic Disasters in Japan

More than 60 volcanic hazard maps have been published on 38 of Japan’s 108 active volcanoes. Two maps were published before 1990, 17 after the 1991 eruptions of Unzen, and 19 after the 2000 eruptions of Usuzan and Miyakejima. Large eruptions greatly increase concern over volcanic hazards. The earlier academic maps themselves have changed from being specialist-oriented to being designed to be more easily understood with volcanic terms clearly explained. This is especially true of revised maps. The 1961 Disaster Countermeasures Basic Act directs that local disaster management plans be promoted by local governments, but only 5 of the local governments in the 25 prefectures neighboring on active volcanoes have set up established specific volcano-oriented antidisaster programs. Others mention volcanic disaster measures in the context of general or storm and flood disaster measures, and another six make no mention of particular measures for volcanic disasters. This lack of concern is somewhat understandably related to budget policies, but real-time hazard maps with probability tree algorithms for forecasting volcanic events are needed to manage potential volcanic disasters effectively. For this purpose, volcanic disaster measures with volcanic risk, or threat analyses assessments must be completed, but no local governments have yet conducted assessments of volcanic risk analyses. Whatever and however complex the reasons, local governments should, cooperating with volcanologists and supported by local residents, take action before an eruption next occurs.

Revised stratigraphy and eruption rates of Ceboruco stratovolcano and surrounding monogenetic vents (Nayarit, Mexico) from historical documents and new radiocarbon dates

More than a dozen new radiocarbon dates reconstruct the eruptive history of Ceboruco volcano. Six of these further constrain previous results for the important plinian Jala eruption, which occurred near 1060 ± 55 yr BP. A calibrated radiocarbon age of AD 990–1020 was obtained as best overlap range for all samples. Pottery fragments found directly underneath the pumice deposit indicate that this area was inhabited by human populations that witnessed the eruption. This age therefore represents an important time marker in the prehistory of this region, because an area of > 560 km2 was devastated and covered by a thickness of > 50 cm of pumice and ash fallout. After the prominent Jala eruption (VEI = 6), at least seven major lava flows and several smaller domes were issued from Ceboruco's crater. Analysis of historical documents allows us to conclude that most of these eruptions took place well before the arrival of the Spanish conquerors to this area in 1528. Ceboruco's last historic eruption (1870–1872) produced a ca. 7 km long viscous dacite lava flow. Its emplacement was accompanied by block-and-ash flow activity and deposition of ash fallout. Because a repeat of such an eruption in the future would seriously endanger the nearby population and disrupt important life-lines, a detailed discussion of eyewitness accounts and other documents, including drawings and paintings is provided. Some of these materials are made available to the broader public for the first time in the present article. Several surrounding monogenetic vents were previously dated by others using the K–Ar and the Ar–Ar methods. Because these dating methods are often not suitable for very young rocks, we also dated several Holocene monogenetic vents by the radiocarbon method. These dates together with geologic mapping allowed calculating eruption rates and recurrence intervals of different types of eruptions. Accordingly, an andesite/dacite lava flow (accompanied by block-and-ash flow activity) was erupted from Ceboruco's crater on average every 143 years during the last 1000 years. In contrast, a monogenetic eruption forming either a scoria cone or a dome has occurred in the area surrounding Ceboruco on average every 1000 years during the Holocene. During the period between AD 1000 and AD 1500 Ceboruco displayed an elevated activity experiencing a rhyodacite plinian eruption (3–4 km 3 DRE) followed by the emplacement of six andesitic/dacitic lava flows also with a total volume of 3–4 km 3. All these figures indicate that the Ceboruco volcanic region is one of the most active areas in the entire Trans-Mexican Volcanic Belt. Consequently, production of a detailed volcanic hazard map and implementation of other preventive measures aimed at reducing potential losses in case of renewed volcanic activity should be mandatory.

Hazard map of El Chichón volcano, Chiapas, México: Constraints posed by eruptive history and computer simulations

El Chichón volcano consists of a 2-km wide Somma crater compound cone 0.2 Ma old with peripheral domes with a central crater reactivated several times during the Holocene. The most recent eruption at El Chichón occurred from March 28 to April 4, 1982, resulting in the worst volcanic disaster during historical times in Mexico, killing more than 2000 people and destroying nine towns and small communities. The volcanic hazard map of El Chichón is based on detailed field work that documented twelve eruptions during the last 8000 years, and computer simulations. To validate the results, computer simulations were first performed over pre-1982 topography mimicking the extent of the actual deposits produced and afterwards run over post-1982 topography. These eruptions have produced pyroclastic fall, surge, flow and lahar deposits. Pyroclastic flows have different volumes and Heim coefficients varying from 0.2 (pumice flows), to 0.15 (block-and-ash flows) and 0.10 (ash flows). Simulations using FLOW3D and TITAN2D indicate that pumice flows and block-and-ash flows can fill the moat area and follow main ravines up to distances of ca. 3 km from the crater, with no effect on populations around the volcano. On the other hand, more mobile ash flows related to column-collapse events can reach up to 4 km from the vent, but will always follow the same paths and still not affect surrounding populations. The energy-cone model was used to simulate the outflow of pyroclastic surges based on the 1982 event ( H/ L = 0.1 and 0.2), and shows that surges may reach some towns around the volcano. Explosive activity also produced Plinian columns higher than 27 km that were dispersed towards the NE by prevailing winds. Future fallout will seriously disturb the lives of more than 70,000 inhabitants of cities and towns located in a radius of 35 km from the volcano. Lahar events in the past originated from unconsolidated pyroclastic deposits with volumes varying from 1 to 4 × 10 6 m 3 for single pulses, to a large one from dam-breakout with a volume of 40 × 10 6 m 3. We used the LAHARZ code to model future events with volumes of 1, 2, and 3 × 10 6 m 3 that will reach as far as 10, 14, and 16 km from the crater, posing some danger to the communities of Nicapa, Volcán, and Ostuacán, even some time after the climax of the eruption.

Automatic GIS-based system for volcanic hazard assessment

This paper presents an automatic system for the elaboration of volcanic hazard maps and scenarios. The methodology used for the generation of both maps is based on the use of numerical simulation of eruptive processes. The system has been developed in a Geographical Information System (GIS) framework, where models for the numerical simulation of different volcanic hazards have been integrated. The user can select in a toolbar one hazard and then decide whether to generate a scenario map (usually with a unique vent) or a hazard map (generally with a broader source area). Once the input parameters are selected, the system automatically generates the corresponding map. The system also incorporates a module to determine the spatial probability of vent opening, as this could be an important parameter for the computation of hazard maps. The tool has been designed in such a way that the inclusion of new numerical models and functionalities is rather easy. Each numerical model is programmed and implemented as an independent program that is launched from the system and, when it finishes the computation, returns the control to the GIS, where the results are shown. This structure allows that further analyses (specifically, risk analyses, that use as an input a hazard or a scenario map), could be also automated inside the system. Additional information, including tutorial and downloadable files can be found in www.gvb-csic.es.

On the Public Attitudes to the Volcanic Hazards and Hazard Map after the Publication of Yakedake Volcanic Hazard Map

On the Public Attitudes to the Volcanic Hazards and Hazard Map after the Publication of Yakedake Volcanic Hazard Map

Display of the Nevado del Ruiz Volcanic Hazard Map Using GIS

The November 13, 1985 Nevado del Ruiz volcanic eruption that killed approximately 25.000 people was the fourth largest volcanic disaster in human history. Different versions of the volcanic hazard map of this volcano were prepared before and after the disaster, being the first map of its kind made in Colombia. Preparation of the hazard maps was not timely, and there was poor dissemination of its content. The Volcanic Hazard Map of Nevado del Ruiz Volcano was recently incorporated into a GIS, in order to make it accessible to both casual and expert users. It was simplified showing only the zones likely to be affected by given volcanic processes. For the volcano's area of influence, perspective views were generated by combining topographic data with the hazard map polygons superimposed on a Landsat TM 5 mosaic. Database visualization in 3‐D enabled complex volcanic hazard data, to be more readily understood by decision makers and the general public.

Holocene volcanic geology, volcanic hazard, and risk on Taveuni, Fiji

The Holocene volcanic geology of Taveuni has been mapped in order to produce a volcanic hazard and risk assessment for the island. Taveuni is the third‐largest island of the Fiji group and home to 14 500 people. At least 2.7 km3 of olivine‐alkali‐basalt magma was erupted from over 100 events throughout the Holocene. Vents are concentrated along a northeast‐striking rift zone that is parallel to other regional structural trends. There is an overall trend of younging southward along the rift. Holocene lavas and tephras are grouped within six newly defined eruptive periods, established on a basis of radiocarbon dating. Within these periods, 14 tephra layers, useful as local marker horizons, are recognised. At least 58% of Holocene eruptions produced lava flows, while almost all produced some tephra. Individual eruption event volumes ranged between 0.001 and 0.20 km3 (dense rock equivalent). Many eruptions involved at least some phases of phreatic and/or phreato‐magmatic activity, although dominant hydrovolcanic activity was limited to only a few events. A volcanic hazard map is presented, based on the Holocene geology map and statistical analyses of eruption recurrence. The highest levels of ground‐based and near‐vent hazards are concentrated along the southern portion of the island's rift axis, with the paths of initial lava flows predicted from present topography. Tephra fall hazards are based on eruption parameters interpreted from mapped Holocene tephra layers. Hawaiian explosive‐style eruptions appear to be a dominant eruptive process, with prevailing low‐level (<3 km) southeasterly winds dispersing most tephra to the northwestern quadrant. Vulnerable elements (population centres, infrastructure, and economy) on Taveuni have been considered in deriving a volcanic risk assessment for the island. A number of infrastructural and subdivision developments are either under way or planned for the island, driven by its highly fertile soils and availability of freehold land. The area identified with the present greatest volcanic risk, in south Taveuni, is also where rapid and ongoing population growth is centred. The results from this study may be used within planning strategies to minimise vulnerability of future developments on the island as well as contributing to national and community‐level emergency or contingency plans.

Lahars at Merapi volcano, Central Java: an overview

Merapi volcano, in Central Java, is one of the most active volcanoes in the world. At least 23 of the 61 reported eruptions since the mid-1500s have produced source deposits for lahars. The combined lahar deposits cover about 286 km 2 on the flanks and the surrounding piedmonts of the volcano. At Merapi, lahars are commonly rain-triggered by rainfalls having an average intensity of about 40 mm in 2 h. Most occur during the rainy season from November to April, and have average velocities of 5–7 m/s at 1000 m in elevation. A wide range of facies may be generated from a single flow, which may transform downvalley from debris flow to hyperconcentrated streamflow. Because of the high frequency and magnitude of the lahar events, lahar-related hazards are high below about 450–600 m elevation in each of the 13 rivers which drain the volcano. Hazard-zone maps for lahar were produced by Pardyanto et al. (Volcanic hazard map, Merapi volcano, Central Java (1/100,000). Geol. Surv. of Indonesia, Bandung, II, 4, 1978) and the Japanese–Indonesian Cooperation Agency (Master plan for land conservation and volcanic debris control in the area of Mt Merapi, Jakarta, 1980), but these maps are of a very small scale to meet modern zoning requirements. More recently, a few large-scale maps (1/10,000- and 1/2000-scale) and risk assessments have been completed for a few critical river systems.

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.

Third version of the hazard map of Galeras Volcano, Colombia

Galeras is an andesitic stratovolcano whose activity is generally characterized by vulcanian eruptions. Based on 14C dating, the active cone is considered to be 5000 years old. During that time, six major periods of eruptive activity have been identified, together with 45 individual events of pyroclastic flows, tephra falls, lava flows and lahars, excluding those reported in historic time ( < 500 years) and those which have occurred since the first signs of the current activity (1988). The stratigraphy of the past 5000 years reveals that the most common events are pyroclastic flows, constituting the principal volcanic hazard of Galeras. Additionally, lava extrusion, tephra falls, and lahars have also occurred, but are lesser hazards. The two previous hazard maps of Galeras did not account for the studies mentioned above. Methodology for this revision of the volcanic hazard map of Galeras is based on (1) probabilistic zoning of phenomena associated with eruptions that have occurred during the past 5000 years and (2) modeling of other phenomena which did not appear in the geologic record, such as shock waves and ballistic projectiles. The map consists of three categories of hazard zones: high, medium and low. The zone of high hazard is defined principally by the distribution of pyroclastic flow deposits, while the zone of low hazard is defined by tephra fall deposits. The medium hazard is a transition zone and ideally, if based on the geological record, does not include pyroclastic flows; however, it is possible that a comparatively large pyroclastic flow could extend into this zone. Additionally, this zone defines the possible trajectories of secondary lahars.

A desktop image processing and photogrammetric method for rapid volcanic hazard mapping: application to air-photo interpretation of Mount Pelée, Martinique

A desktop image processing and photogrammetric method was developed for digitizing black-and-white aerial photographs. The technique was applied to airborne optical images of Mt. Pelee, Martinique, a historically active volcano in the tropical Lesser Antilles island arc, to evaluate its utility for rapid geologic mapping and hazard assessment in vegetated areas. The digital approach provides several advantages over traditional air-photo interpretation by allowing for change detection in time-series images, morphologic characterization, development of digital elevation models from stereopairs, and geo-referencing with other digital data sets. A digital mosaic of Mt. Pelee was created from air photos acquired in 1951, which covered the region affected by the 1902 eruption. Severe mismatches occurred along edges of adjacent photographs prior to correction, which precluded quantitative morphologic analysis of the volcanic edifice. Geometric corrections and histogram equalization of digitized air photos allowed creation of a continuous mosaic. Comparison of the mosaic and a map based on differences in gray scale and texture to a volcanostratigraphic map revealed that not only the various deposits produced during the 1902 event were easily differentiated, but that older eruptive products were identified, suggesting that this approach may be used for rapid hazard evaluation of historically active tropical volcanoes.

A desktop image processing and photogrammetric method for rapid volcanic hazard mapping: application to air-photo interpretation of Mount Pelée, Martinique

A desktop image processing and photogrammetric method for rapid volcanic hazard mapping: application to air-photo interpretation of Mount Pelée, Martinique

The Platanar-Aguas Zarcas volcanic centers, Costa Rica: spatial-temporal association of Quaternary calc-alkaline and alkaline volcanism

The Platanar volcanic center is dominated by a calc-alkaline, basalt-andesite-dacite-rhyolite magma series with unusual LREE enrichment. Adjacent and overlapping the calc-alkaline rocks are the most alkaline basalts found along the volcanic front of Central America. These basalts are mafic, LIL- and LREE-enriched transitional to alkaline basalts. Several are found on the north flank of Platanar in the Aguas Zarcas region, where there are nine cinder cones and a few isolated flows. However, they are also found in isolated lava outcrops at least as far south as Porvenir volcano along the volcanic front. The addition of mafic alkaline magmas with high La/Yb and low Ba/La into the Platanar magma chamber or chambers may contribute to the LREE-enriched character of the Platanar basaltic andesites and andesites. At Platanar the field and geochemical evidence suggest mixing between calc-alkaline and alkaline magmas, a process that has probably occurred throughout the development of the Cordillera Central of Costa Rica. The presence of negative Ce anomalies in several of the calc-alkaline lavas also make the Platanar complex very unusual compared to the rest of the Central American volcanic front. In the center of the Platanar complex is the Chocosuela caldera, an apparent remnant of an avalanche caldera created by the collapse in the Middle Pleistocene of an ancestral stratovolcano toward the NNW in a directed blast-type eruption. Rhyolite is present as pumice lapilli in pyroclastic flow deposits outside the caldera rim. Whole lapilli analyses span the daciterhyolite range. The previous eruption of high silica tephra as pyroclastic flows, the current long dormant period and the repeated occurrence of earthquake swarms on the flanks of the Platanar complex make it a candidate for volcanic hazard mapping, detailed geological mapping and emergency planning.

Computer-Assisted Mapping of Pyroclastic Surges

Volcanic hazard maps of surge boundaries and deposit thickness can be created by using a simplified eruption model based on an "energy line" concept of pyroclastic surge and flow emplacement. Computer image-processing techniques may be used to combine three-dimensional representations of the energy relations of pyroclasts moving under the influence of gravity (defined by an "energy cone") with digital topographic models of volcanoes to generate theoretical hazard maps. The deposit boundary and thickness calculated for the 18 May 1980 eruption of Mount St. Helens are qualitatively similar to those actually observed.

Pyroclastic block flow from the September, 1976, eruption of La Soufrière volcano, Guadeloupe

ERUPTION A phreatic eruption occurred at 19:22 H from a new set of fissures on the southeast side of the summit dome. The steam jet from the narrow fissure incorporated accessory fragments of the e~sting dome that ranged in size from 3 m blocks down to particles of a few microns in diameter. No juvenile material was erupted. The branching 550 m pyroclastic block flow is surrounded by a zone of total destruction extending out to 900 m from the vent. An outer zone of directed blast projects to at least 1500 nm Profiles of the destructive cloud and the pyroclastic flow allow energy decay curves to be constructed for this eruption. From these curves the potential surface for flows associated with this type of phreatic eruption can be constructed as an initial step in developing a volcanic hazard map.

Assessing volcanic risk

The assessment of volcanic risk is vital in areas of social and/or economic importance. Volcanic risk is denoted by the probability that an event of a certain type and magnitude will occur within a specified time period and will affect a designated area, and is a factor which must be evaluated with regard to the different types of volcanic hazards and their various degrees of severity. New methods for the presentation of data in volcanic hazard and risk maps are introduced, and proposals are made for high-risk areas, especially those where volcanoes have particularly long repose periods.