Potential Volcanic Hazards Research Articles

Quantifying systemic vulnerability of interdependent critical infrastructure networks: A case study for volcanic hazards

Infrastructure networks are vital for the communities and industries that rely on their continued operation. Disasters stress these complex networks and can provoke systemic disruptions that extend far beyond the spatial footprint of hazards. An enduring challenge for assessing infrastructure networks within disaster impact assessment frameworks has been to adequately quantify the high spatial interdependence of these networks, and to consider risk management interventions through time. This is of particular importance for volcanic eruptions, which can produce multiple hazards over highly variable spatiotemporal extents. In this study, we present a methodology for the quantification of systemic vulnerability of infrastructure networks, which can be coupled with physical vulnerability models for the purpose of impact assessment. The two-part methodology first quantifies the haard-agnostic criticality of infrastructural components, inclusive of interdependencies, and then incorporates representative hazard spatial footprints to derive the systemic vulnerability. We demonstrate this methodology using the case study of volcanic eruptions from Taranaki Mounga volcano, Aotearoa New Zealand, where there are many industrial sites of national importance, and a high likelihood of a complex multi-hazard volcanic eruption. We find a considerable increase in the systemic vulnerability of electricity and natural gas network components after incorporating infrastructure interdependencies, and a further increase in the systemic vulnerability of these critical components when cross-referenced with potential volcanic hazard spatial extent. The methodology of this study can be applied to other areas of interest in both its hazard-agnostic or hazard-dependent form, and the systemic vulnerability quantification should be incorporated into impact assessment frameworks.

The magmatic plumbing beneath the Wudalianchi volcanic region, northeast China, is recharged by magma reservoirs under Keluo volcano

The intraplate magmatic systems of the Wudalianchi potassic volcanic region in northeast China have historically exhibited eruption activity, and there is evidence that they retain the potential for future eruptions. However, the characteristics of this complex volcanic region remain debated and poorly understood due to the relatively low resolution of existing crustal tomography. Here we present a high-resolution shear-wave velocity model of the crust and uppermost mantle obtained by applying full-waveform ambient noise tomography to data recorded at 106 recently deployed broadband seismic stations. Our results reveal two vertical low-velocity anomalies discovered beneath the Nuominhe and Keluo volcanoes, which appear to be magma ascending pathways connecting a mantle source and crustal reservoirs. A horizontally interconnected low-velocity zone in the middle-lower crust indicates a magmatic migration pathway transporting potassium-rich melts directly among the potassic volcanic units. In addition, the Wudalianchi volcano is likely recharged by deeper and larger crustal magma reservoirs under the Keluo volcano. The unique geometries of the magmatic plumbing systems provide valuable seismic evidence for the volcanic eruption dynamics and potential volcanic hazards.

Assessing volcanic hazard and exposure in a data poor context: Case study for Ethiopia, Kenya, and Cabo Verde

Volcanoes produce a wide variety of hazards across varying spatial and temporal scales. When data are scarce on past eruptions and hazards, it can falsely imply low hazard recurrence and create challenges for robust hazard and risk assessment. Data quality and quantity vary considerably across different regions, volcanoes, and eruptions. Yet, there is a need for regional to global scale information on volcanic hazard and risk, where consistent and reproducible methods are applied. Such information is used by international stakeholders to inform funding priorities, risk reduction policies, and to highlight data and knowledge gaps, contributing towards the Sendai Framework's Sustainable Development Goals. Challenges in gathering this information can be most problematic where large populations are exposed to potential volcanic hazards but there are few comprehensive eruptive histories, as in sub-Saharan Africa. Here, we present a unique study to evaluate hazard and exposure for nine volcanoes in Ethiopia, Kenya and Cabo Verde, as part of an international project to develop multi-hazard Disaster Risk Country Profiles. We applied a two-stage expert elicitation process to volcanoes for the first time, and coupled the results with vent mapping, numerical hazard modelling, and GIS analysis of eight exposure categories to identify where high volcanic hazard and exposure coincide. Testing the sensitivity of our findings to input assumptions, to better understand where uncertainties lay, showed that improving our knowledge of past eruption volumes, frequencies, and dates was key to reducing uncertainty. Expert elicitations proposed that Fogo, Cabo Verde, is the most likely to erupt (eruption on average every 25 years), while Fentale (Ethiopia), Longonot and Suswa (Kenya) were elicited to have the greatest probability for a large explosive (VEI ≥ 4) eruption (on average every 400 years). Menengai and Longonot produce the larger exposure values across most VEI scenarios and categories of exposure, but population and GDP exposure was also large for more distal tephra fall and flows at Corbetti and Suswa, with order of magnitude increases expected between 2010 estimates and 2050 projections. Potentially high impact scenarios include tephra being dispersed across large cities (e.g. Nairobi, 55 km from Suswa) and key infrastructure (e.g. geothermal power station ∼2.5 km from Aluto), as well as important tourist destinations, seats of government and emergency management operations (e.g. islands east of Fogo). This study provided the first hazard and exposure assessment of its kind for these volcanoes and drew attention to volcanic risk at the levels required to inform policy and future in-country funding opportunities.

A history of explosive eruptions at Young Damavand volcano, Iran

Young Damavand volcano is a steep isolated volcano in the Central Alborz Mountains, Iran, that is characterized by extensive lava flows and pyroclastic successions and is placed on the eroded remains of Old Damavand. Pyroclastic fall and density current deposits on all flanks of the volcano were sampled and studied. From a tephrostratigraphic and geochemical study of the proximal-medial sequences, 14 phases of explosive volcanic activity are identified, characterized by a combination of ash and pumice fall deposits, and/or dense and dilute pyroclastic density current deposits. Some explosive phases of Damavand are thought to have happened one after the other with only short time intervals, since almost no traces of paleosol can be identified between them. We also show that the intensity of the eruptions varied between different phases, confirmed by relative thickness and grain size of the different fall deposits and their distance from the crater. The evidence of numerous explosive eruptions, five of which with Volcanic Explosivity Index 4 in the history of the activity of Young Damavand volcano, shows the importance of assessing its potential volcanic hazards.

SPATIAL ANALYSIS OF VOLCANIC ASH DISTRIBUTION DUE TO VOLCANIC ERUPTION IN JAVA ISLAND

Abstract. Indonesia is located on the Ring of Fire with the most geologically active than any other countries, which makes it vulnerable due to the massive earthquakes and volcanic eruptions. Java Island has the most active volcano with high risks such as human risk and infrastructure from volcanic ash because of volcanic eruptions. The availability of the map of potential volcanic hazards is important to help mitigate the risk caused by volcanic eruptions. However, to the best of the author's knowledge, the distribution of volcanic ash has never been assessed in detail in the disaster-prone hazard map published by the Centre for Volcanology and Geological Hazard Mitigation (CVGHM), Indonesia. This research reported the potential distribution of volcanic ash due to volcanic eruptions in the future in Java island. Following the principles of Probabilistic Hazard Assessment and TephraProb software, the modeling of volcanic ash potential was performed using various parameters such as historical data, eruption source parameter, total grain-size distribution, tephra2 parameter, and the wind speed around the volcanoes as an input. The map shows the distribution of volcanic ash based on the volcanic ash accumulation (kg/m2) and the volcanic ash hazard map is classified into three classes. There are 19 models of volcanic ash distribution with various probabilities of exceedance based on 19 A-type volcanoes on Java Island. This volcano's distribution of volcanic ash tends to the southwest as the wind speed and direction.

Thermal structure beneath Changbaishan Volcano, northeastern Asia: new insights from temperature logging and numerical modelling

SUMMARY Changbaishan Volcano is considered one of the most hazardous active volcanic fields in northeastern Asia, and it has been the subject of increasing concern due to its unrest from 2002 to 2006. The physical conditions of magma chambers in the crust, particularly temperature and pressure, are crucial factors that determine the tempo and magnitude of volcanic eruptions, which are closely linked to potential hazards. However, the lithospheric thermal structure, which strongly influences rheological behaviour and melting, has been poorly studied. We conducted direct geothermal measurements and numerical forward modelling to address this issue to confirm whether a crustal magma chamber lies beneath the caldera as in earlier geophysical interpretations. We first reported four heat-flow data sets in Changbaishan Volcano. The research findings indicate that the heat flow value near the Tianchi caldera is remarkably high, at 270±16 mW m−2. As the distance from the caldera increases, the heat flow gradually decreases to a normal continental heat flow value of 75 mW m−2. 3-D transient heat simulations with a magma cooling model and a continuous magma supply model demonstrate the thermal effect of the magma chamber. The best-fitting model for the Tianchi magma system is an ellipsoidal magma chamber with a depth of 8–14 km, a 20 km east–west axis and a 70 km north–south axis, supplied with magma from the asthenosphere for 2 Myr. The high surface heat flow and crustal temperatures suggest that magma is active beneath Changbaishan Volcano within the middle-upper crust, and volcanic reactivation could occur. Thus, further research on the lithospheric thermal structure is necessary to understand the potential volcanic hazards associated with Changbaishan Volcano.

Delineating a volcanic aquifer using groundwater-induced gravity changes in the Tatun Volcano Group, Taiwan

The Tatun Volcanic Group (TVG) is an active volcanic system that poses potential volcanic hazards to northern Taiwan. Groundwater migration can be sensitive to volcanic activities and can induce temporal gravity changes. Here we conducted four gravity measurement campaigns in 2012 with two CG5 relative gravimeters at a total of 31 gravity monitoring sites to probe the spatiotemporal groundwater variability in the TVG area. With careful adjustments to the gravity measurements, the standard point gravity error was approximately 8 μGal on average. The observed gravity changes were compared with the groundwater-induced gravity variations derived from two hydrological models: the continuous flow model that consisted of one permeable layer (Model A) and a dynamic groundwater flow model that used the hydrological solver MODFLOW (Model B). The results show that only gravity observations in the central TVG match the simulated gravity pattern, i.e., the hydrology in the central TVG follows free groundwater flows within the interconnected and porous strata. On the other hand, inconsistencies between simulated and observed gravity changes range from + 40 to – 80 μGal. The discrepancies were located at the eastern and western areas in the TVG and showed opposite variations over time. This pattern of temporal variability cannot be attributed to the use of shallow aquifer models that merely reflect the surface recharges and discharges. We infer that the pattern stems from deep flows, such as hydrothermal fluids alternately replenishing aquifers to the east and west of the TVG, i.e., deep fluid conduits may have developed to the east and west of the TVG and bypassed the central area.

Re-investigation of the sector collapse timing of Usu volcano, Japan, inferred from reworked ash deposits caused by debris avalanche

It is essential to establish the timing of past sector collapse events at a volcanic edifice to evaluate not only the evolution of the volcanic system but also potential volcanic hazards. This can be done by determining the age of the collapse-generated debris avalanche deposits. However, without evidence of an associated magmatic eruption, it is impossible to recognize juvenile materials in these deposits. Thus, it is usually difficult to determine the precise age of sector collapse. Usu is a post-caldera volcano of the Toya Caldera (Hokkaido, Japan) and has been constructed since ca. 19–18 ka on top of the caldera-forming Toya pyroclastic flow deposits (Tpfl deposit: 106 ka). A sector collapse occurred after the formation of a stratovolcano edifice and produced the Zenkoji debris avalanche (ZDA) deposit with reported ages ranging from >20 to 6 ka. We investigated the tephrostratigraphy preserved in the soil above the ZDA deposit and in the surrounding area and recognized fine ash fall deposits at two locations, above and east of the ZDA deposit. The glass shards within these deposits were correlated with several tephra layers with the majority being derived from Tpfl deposits. Thus, these ash deposits should be considered reworked tephra. A considerable number of hummocks in the ZDA deposit were also composed of deformed and fragmented Tpfl deposits, which suggests that the ZDA bulldozed and partially incorporated the Tpfl deposit on the flank of the volcano. Deformation and fragmentation of the non-welded soft silicic Tpfl deposit during the transport and emplacement of the ZDA produced an accompanying ash cloud, which deposited the observed glassy, fine, ash fall units. Radiocarbon dating of soil samples directly below and above the reworked ash deposits allowed dating the sector collapse to ca. 8 ka. This age is much younger than previously proposed results. Based on our findings, the transport and emplacement mechanism of the sector collapse should be revised. Our study shows that reworked ash layers caused by the flow of a debris avalanche can be used as an indicator of the timing of a sector collapse of the volcano.

Large-scale magmatic–hydrothermal system of Kusatsu-Shirane Volcano, Japan, revealed by broadband magnetotellurics

Kusatsu-Shirane Volcano (KSV) is an active volcano in the central Honshu Arc, Japan, and is known for its significant hydrothermal activity and repeated phreatic eruptions over the past 200 years. On the basis of its long-term volcanic activity, an extensive magmatic–hydrothermal system is considered to have developed within the volcano, with strong impacts on volcanic processes. Previous magnetotelluric studies conducted at KSV have successfully revealed the structure of the hydrothermal system, mainly beneath the summit area. However, as the deep structure was still unclear, there was no information on the location of magma storage as a heat source to drive volcanic activity. Here we report a revised three-dimensional electrical resistivity structure model for KSV down to a depth of ~10 km below sea level (bsl), inferred from broadband magnetotelluric data (256–0.004 Hz) collected over a wider area than previous studies. The most notable feature of the model is a sub-vertical conductive zone that extends from a depth of 1.5 km below the summit area to a depth of ~10 km in the north-northwestern part of KSV. We interpret resistivity values to infer the upper half of the conductive zone (<4 km bsl) as a zone containing high-salinity brine and the lower half (>4 km bsl) as a partially molten zone. The fact that the inflation source during the unrest periods is located just beneath the brine zone indicates that the lower partially molten zone contains degassing magmas. This partially molten zone extends beneath the adjacent Shiga Volcano, suggesting that the two volcanoes could share a common magma source. The brine zone in the upper half is considered to have formed as a result of repeated magmatic intrusions during the Stage III activity of KSV since 17 ka. As this brine zone is not found beneath the presently inactive Shiga Volcano, it is considered that the formation of brine zones could be used as an indicator for evaluating recent magmatic activity and potential volcanic hazards.

An external event identification for Nuclear Power Plant (NPP) siting project at West Kalimantan, Indonesia

The research aims to determine the existing external event for Nuclear Power Plant (NPP) Siting project at West Kalimantan. The identification of external hazard potential studies is carried out based on the IAEA safety guide and BAPETEN regulations regarding external potential hazards which include seismic aspects, surface faults, extreme meteorology, geotechnics, volcanoes which must be carried out in determining the NPP’s site. The method used in this research is field ground check and desk work analysis with references related to identified external hazards. The results showed that the potential site of the NPP’s in West Kalimantan Province is safe from potential external natural hazards. The NPP’s site has also been determined to be safe from the dangers of flooding due to tsunamis and flood overflows, no capable faults are found, and far from potential volcanic hazards. Extreme meteorological potential is rare at site sites. To evaluate the oceanography aspect, the existence of physical oceanographic conditions must be carried out in-depth studies in the future, especially related to the sedimentation process that has occurred around the nuclear power plant site.

Eruption Sequences and Characteristics of Weizhou Island Volcano, Guangxi Province, South of China

Weizhou island, located in the north margin of the South China Sea (SCS), is characterized by multi-stage volcanism, several eruption styles and eruption craters, and is also the youngest Quaternary volcanic island in China. An eruption on this island may pose high risk to life and property. However, the eruptive history of Weizhou island, the craters number and location, and their eruptive sequence and characteristics are still being debated, which are important for potential volcanic hazard assessment. In the present study, field surveys, 40Ar/39Ar and 14C geochronological studies and whole rock composition analysis of volcanic rock are used to investigate the eruption sequences associated with Weizhou island and the characteristics of each period. Four volcanoes were discovered at Henglushan, Hengling, Nanwan and Daling. The Henglushan and Hengling volcanoes were produced by early weak explosive and late effusive eruptions, and lavas from these volcanoes represent the foundation of island. Conversely, the Nanwan and Daling volcanoes are linked to multiple explosive eruption phases, with hydromagmatic eruptions in the first and last phase and a magmatic explosive eruption in the second phase. The pyroclastic density currents (PDCs) deposits of the Nanwan and Daling volcanoes virtually cover the entire island. Volcanic activity in Weizhou island started in Early Pleistocene and ended in Late Pleistocene. This can be divided into the following distinct periods: 1,420–1,260, 870–740, 600–480, 283–222 ka, and 33.7–13 ka. The first four periods were dominated by effusive eruptions associated with the Henglushan and Hengling volcanoes, which peaked between 870 and 740 ka. After this period, explosive eruptions began at around 33.7 ka because of magma–water interactions. These explosive eruptions then created the Nanwan and Daling volcanoes. Early effusive lava flows in Weizhou island are characterized by basaltic compositions and are linked with a small amount of fractional crystallization. Magmas in later eruptions contained slightly lower SiO2 and involved some basanite. Fractional crystallization was also less pronounced in these lavas because of their rapid ascent.

Stratigraphy, chronology, and magma evolution of Holocene volcanic products from Mt. Slamet deposited in the Guci Valley, Central Java, Indonesia

The active cone of Mt. Slamet is situated above the Guci Valley, making it vulnerable to volcanic eruptions. This is a fast-growing resort area with a permanent population of thousands and annual visitation in the hundreds of thousands. In this study, we combined stratigraphic observations with petrologic and geochemical analysis of volcanic rocks deposited in the valley to better understand the potential volcanic hazards. Within 7–9 km from the summit, the valley contains four massive lavas, seven pyroclastic density current deposits, one scoria fall, and one lahar deposit. Two of the three massive pyroclastic density current deposits (3–15 m thick) were dated to 8040 ± 30 BP and 3910 ± 30 BP; the third was overlain by the 8040 ± 30 BP deposit. Therefore, during the Holocene at least 7 explosive eruptions have occurred at Mt. Slamet. The valley's volcanic deposits were characterized by lower CaO numbers, higher FeO*, and higher FeO/MgO ratios than older products from Mt. Slamet, representing a distinct character of modern magma. Thus, our stratigraphic record suggests that the Guci Valley may be exposed to future eruptive activity with corresponding hazards to the population.

Dilemma of Geoconservation of Monogenetic Volcanic Sites under Fast Urbanization and Infrastructure Developments with Special Relevance to the Auckland Volcanic Field, New Zealand

Geoheritage is an important aspect in developing workable strategies for natural hazard resilience. This is reflected in the UNESCO IGCP Project (# 692. Geoheritage for Geohazard Resilience) that continues to successfully develop global awareness of the multifaced aspects of geoheritage research. Geohazards form a great variety of natural phenomena that should be properly identified, and their importance communicated to all levels of society. This is especially the case in urban areas such as Auckland. The largest socio-economic urban center in New Zealand, Auckland faces potential volcanic hazards as it sits on an active Quaternary monogenetic volcanic field. Individual volcanic geosites of young eruptive products are considered to form the foundation of community outreach demonstrating causes and consequences of volcanism associated volcanism. However, in recent decades, rapid urban development has increased demand for raw materials and encroached on natural sites which would be ideal for such outreach. The dramatic loss of volcanic geoheritage of Auckland is alarming. Here we demonstrate that abandoned quarry sites (e.g., Wiri Mountain) could be used as key locations to serve these goals. We contrast the reality that Auckland sites are underutilized and fast diminishing, with positive examples known from similar but older volcanic regions, such as the Mio/Pliocene Bakony–Balaton UNESCO Global Geopark in Hungary.

Load Stress Controls on Directional Lava Dome Growth at Volcán de Colima, Mexico

During eruptive activity of andesitic stratovolcanoes, the extrusion of lava domes, their collapse and intermittent explosions are common volcanic hazards. Many lava domes grow in a preferred direction, in turn affecting the direction of lava flows and pyroclastic density currents. Access to active lava domes is difficult and hazardous, so detailed data characterizing lava dome growth are typically limited, keeping the processes controlling the directionality of extrusions unclear. Here we combine TerraSAR-X satellite radar observations with high-resolution airborne photogrammetry to assess morphological changes, and perform finite element modeling to investigate the impact of loading stress on shallow magma ascent directions associated with lava dome extrusion and crater formation at Volcan de Colima, Mexico. The TerraSAR-X data, acquired in ~1-m resolution spotlight mode, enable us to derive a chronology of the eruptive processes from intensity-based time-lapse observations of the general crater and dome evolution. The satellite images are complemented by close-range airborne photos, processed by the Structure-from-Motion workflow. This allows the derivation of high-resolution digital elevation models, providing insight into detailed loading and unloading features. During the observation period from Jan-2013 to Feb-2016, we identify a dominantly W-directed dome growth and lava flow production until Jan-2015. In Feb-2015, following the removal of the active summit dome, the surface crater widened and elongated along a NE-SW axis. Later in May-2015, a new dome grew toward the SW of the crater while a separate vent developed in the NE of the crater, reflecting a change in the direction of magma ascent and possible conduit bifurcation. Finite element models show a significant stress change in agreement with the observed magma ascent direction changes in response to the changing surface loads, both for loading (dome growth) and unloading (crater forming excavation) cases. These results allow insight into shallow dome growth dynamics and the migration of magma ascent in response to changing volcano summit morphology. They further highlight the importance of detailed volcano summit morphology surveillance, as changes in direction or location of dome extrusion may have major implications regarding the directions of potential volcanic hazards, such as pyroclastic density currents generated by dome collapse. Introduction

Structure of the shallow magma chamber of the active volcano Mt. Zao, NE Japan: Implications for its eruptive time scales

Zao volcano is one of the representative active stratovolcanoes in northeast Japan, having many historical eruption records, as the last one occurred in 1940. Since 2013 to present, precursory phenomena, such as volcanic tremors and deformation of the summit area, have been detected in this volcano; thus, it is urgently necessary to thoroughly characterize the magma feeding system beneath the volcano. Our aim is to understand the magma chamber structure and dynamics associated with the recent activity (ca. ~2 ka) of Zao volcano in NE Japan. We conducted petrological and geochemical studies in the representative pyroclastic products and youngest lavas of its recent activity. The products are divided into the GSN (Goshikidake-nanbu) pyroclastics, GST (Goshikidake-tobu) pyroclastics and GS lavas (Furikodaki lava and Goshikidake-nanpo lava and associated pyroclastic deposits).The rock samples are calc-alkaline olivine-bearing pyroxene andesites originated as the result of mixing between felsic (containing Mg-poor pyroxenes + anorthite (An)-poor plagioclases) and mafic (containing forsterite (Fo)-rich olivines + An-rich plagioclases magmas). Thermodynamic modelling indicates that the temperature (T)–pressure (P)–water activity (H2O) conditions of the felsic (ca. 60–61 wt% SiO2, 968–1000 °C, 1.6–2.0 kbar and 1.8–2.2 wt% H2O) and the mafic (ca. 48.0–50.5 wt% SiO2, 1113–1170 °C, <2.4 kbar and 1.0–2.2 wt% H2O) end–members are similar between the GSN, GST pyroclastics and GS lavas.Compositional zoning of orthopyroxene phenocrysts suggests the formation of two mixed magmas, namely the main mixed and the Mg-rich mixed ones. The mafic magma from a deeper source entered repeatedly into a shallower felsic magma chamber. As a result, the main mixed magma developed within the chamber. The Mg-rich-mixed magma tentatively developed by the injection and simultaneous mixing of both the main mixed magma and the injected mafic one, merging later on into the main mixed magma.The Fe-Mg diffusion modelling on orthopyroxenes reveal that the injections occurred from <60 days to 1.7 years for thin-darker-zone types, and multiple injections of mafic magma occurred from 2.5 years to 150 years for broad-darker-zone types until the eruptions. The thin-darker-zone type orthopyroxene phenocrysts are abundant in the GSN and GST pyroclastics but rare in the GS lavas. Instead, the broad-darker-zone type orthopyroxenes are rare in the GSN and GST pyroclastics and abundant in the GS lavas. Thus, the main mixed layer was more evolved for the GS lavas than for the GSN and GST pyroclastics. The injected mafic magmas for the GS lavas were merged more extensively than the GSN and GST pyroclastics, resulting in a larger release of volatile components that triggered the effusive episodes. Given that local precursory phenomena have been currently detected in Zao volcano, we are confident that any research to thoroughly characterize the magma feeding system under this active volcano is essential for society to better react to any potential volcanic hazard in the near future.

Geoheritage Values of a Mature Monogenetic Volcanic Field in Intra-continental Settings: Harrat Khaybar, Kingdom of Saudi Arabia

Harrat Khaybar is one of the most extensive of about 15 volcanic fields located in the western margin of the Arabian Peninsula. Most of these fields are located in the Kingdom of Saudi Arabia about 100–150 km inland from the Red Sea. The volcanic area is located near the culturally and religiously important city of Al Madinah. The field hosts monogenetic volcanoes such as scoria cones, tuff rings, spatter cones and extensive lava flow fields. It also contains several silicic lava domes and associated block-and-ash fans whose deposits fill inter-cone regions. Some of the field’s volcanoes are inferred to have been erupted as recently as about 1000 AD, based on historic documents and geomorphologic evidence. There are no data available to directly support or better constrain the timing of the latest eruptions of the field. The area is also one of the highest regions of Saudi Arabia with a plateau at about 1500 m above sea level, topped by Jabal Abyad (2093 m) and Jabal Quidr (2022 m) volcanoes. Due to the elevation, Harrat Khaybar has a cold arid climate with a unique ecosystem and landscape. The region’s high aesthetic value is derived from the bright white colour of several of its volcanoes which are dominantly rhyolitic ash. These edifices are strikingly different from the dark-coloured lava fields (harrats) of Arabia. Based on appearance, Harrat Khaybar has geoheritage value and could be a major geoconservation and geoeducation region of Arabia. Geological research in the region started only recently and is restricted to geological mapping and geochemical studies. Interest has recently increased because of the recognition of the field’s potential volcanic hazards. There is a push to establish a geoheritage inventory of Harrat Khaybar with the aim of assessing the geoheritage framework of the region and developing more geotourism, geoeducational programmes and a geopark. Key volcanic geotopes and their geosites provide unique opportunities for a stand-alone geopark offering geoeducation and geotourism programmes in the region. The concept has been proposed to the geoheritage resource management of Harrat Rahat just south of Harrat Khaybar and Al Madinah City and could serve as a link between the two historically active volcanic fields located near Al Madinah.

Promotion and Development of Protected Volcanic Areas Through Field-Based Environmental Communication Activities: the ‘Gran Cono’ Tour in the Vesuvius National Park (Italy)

The ‘Gran Cono’ tour in the National Park of Vesuvius (Campania, Italy), is, presented here, a scientific event conceived with the aim of testing how field-based communication activities in protected and active volcanic areas could be important in order to draw attention of people towards the geological value of volcanic sites, and also to raise awareness of local high volcanic hazard. The field trip was carried out on October 18, 2014, in the framework of the second year of the ‘Settimana del Pianeta Terra’ (The Week of Planet Earth), the main purpose of this initiative being the discovery and the promotion of Italian geological and natural heritage, and consisted of hundreds of geoevents throughout the country. The Gran Cono walking tour, planned in a very well-known and protected volcanic area, was carried out by about a hundred nonskilled citizens, including children. They could discover and enjoy the extraordinary geodiversity and biodiversity of the Vesuvius environment, but also perceive the potential volcanic hazard of Vesuvius, a still active but quiescent volcano. As a result, the educational value of this field-based environmental communication activity has been achieved through effective communication between the scientists involved and the communities living in a very dangerous volcanic areas. The organization of similar events has proven to be very valuable in such densely populated areas, where the awareness of volcanic risk is often very poor, as they raise public understanding of both the high risk and the inestimable geoheritage associated with their territory.

Deep magma accumulation at Nyamulagira volcano in 2011 detected by GNSS observations

People in the area of the Virunga Mountains, along the borders of the Democratic Republic of Congo, Rwanda, and Uganda, are at very high natural risk due to active volcanism. A Global Navigation Satellite System (GNSS) network, KivuGNet (Kivu Geodetic Network), has operated since 2009 for monitoring and research of the deformation of Nyamulagira and Nyiragongo volcanoes as well as tectonic deformation in the region. We detected an inflationary signal from the position time-series observed in the network using our detection method, which is a combination of Kalman filtering and principal component analysis. The inflation event began in October 2010 and lasted for about 6 months prior to the 2011–2012 eruption at Nyamulagira volcano. The pre-eruptive inflationary signal is much weaker than the co-eruptive signal, but our method successfully detected the signal. The maximum horizontal and vertical displacements observed are ∼9 mm and ∼5 mm, respectively. A Mogi point source at a depth >10 km can explain the displacement field. This suggests that a relatively deep source for the magma chamber generated the inflationary signal. The deep reservoir that is the focus of this study may feed a shallower magma chamber, which is the likely source of the 2011–2012 eruption. Continuous monitoring of the volcanic activity is essential for understanding the eruption cycle and assessing potential volcanic hazards.

Late Pleistocene ages for the most recent volcanism and glacial‐pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

AbstractThe Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east‐central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ∼1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most‐recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well‐preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ∼17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase‐pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ∼17 ka, and produced a lava flow field covering ∼35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo‐Owens Lake during the last glacial cycle.

Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex

In volcanically and seismically active rift systems, preexisting faults may control the rise and eruption of magma, and direct the flow of hydrothermal fluids and gas in the subsurface. Using high-resolution airborne imagery, field observations, and CO 2 degassing data on Aluto, a typical young silicic volcano in the Main Ethiopian Rift, we explore how preexisting tectonic and volcanic structures control fluid pathways and spatial patterns of volcanism, hydrothermal alteration and degassing. A new light detection and ranging (lidar) digital elevation model and evidence from deep geothermal wells show that the Aluto volcanic complex is dissected by rift-related extensional faults with throws of 50–100 m. Mapping of volcanic vent distributions reveals a structural control by either rift-aligned faults or an elliptical caldera ring fracture. Soil-gas CO 2 degassing surveys show elevated fluxes (>>100 g m –2 d –1 ) along major faults and volcanic structures, but significant variations in CO 2 flux along the fault zones reflect differences in near-surface permeability caused by changes in topography and surface lithology. The CO 2 emission from an active geothermal area adjacent to the major fault scarp of Aluto amounted to ∼60 t d –1 ; we estimate the total CO 2 emission from Aluto to be 250–500 t d –1 . Preexisting volcanic and tectonic structures have played a key role in the development of the Aluto volcanic complex and continue to facilitate the expulsion of gases and geothermal fluids. This case study emphasizes the importance of structural mapping on active rift volcanoes to understand the geothermal field as well as potential volcanic hazards.