Monogenetic Volcanoes Research Articles

Tectonic controls on geomorphology and spatial distribution of monogenetic volcanoes in the Central Southern Volcanic Zone of the Andes (Argentina)

Monogenetic volcanoes are among the most common volcanic landforms on Earth. The morphology and distribution of small volcanoes can provide important information about eruption dynamics and tectonics. The Southern Volcanic Zone of the Andes (CSVZ) comprises one of the most active magmatic regions on Earth. Characterized by the presence of polygenetic volcanoes and calderas in a complex tectonic setting, this region also hosts hundreds of small, back-arc monogenetic volcanoes. In this contribution, we apply a Geographic Information System (GIS) that combines imagery data and digital elevation models to establish the first comprehensive dataset of monogenetic volcanoes in the CSVZ (38° to 40° S), exploring their eruption dynamics and relationship to tectonic and structural processes. Combining spatial analysis and geomorphological observations, we identify the presence of 335 monogenetic volcanoes distributed into nine clusters, now grouped in the Zapala Volcanic Field (ZVF). The ZVF is marked by the predominance of cinder cones (80%) followed by phreatomagmatic volcanoes (20%), suggesting some influence of external water in the eruption dynamics. Generally, monogenetic vents present a clear association with local and regional lineaments, suggesting a strong structural control on the occurrence of the monogenetic deposits in the ZVF. The higher vent densities are observed in the southern Loncopué Though, an important extensional feature related to tearing of the subducted Nazca plate underneath the South American Plate. Morphometric parameters of cinder cones indicate variable stress orientations in the CSVZ that possibly results from the oblique tectonics in the region. From north to south, the maximum principal stress rotates from NE-SW to E-W and becomes progressively less constrained as it distances from the current magmatic arc. Based on the relative ages, we map the evolution of monogenetic volcanism through time. Our results suggest a waning in the monogenetic activity in ZVF over time. When compared to monogenetic fields in the Central Andes, the ZVF is marked by higher vent densities and number phreatomagmatic landforms, with the absence of lava domes. This ultimately reflects the contrasting crustal structure and climate conditions of these two regions.

Comment on García et al. (2021) Semicontinuous paleomagnetic record of the last 1 Ma from radiometrically dated igneous rocks (Trans-Mexican Volcanic Belt and surrounding areas) https://doi.org/10.1016/j.jsames.2021.103195

García et al. (2021) analyzed paleomagnetic data from the Trans-Mexican Volcanic Belt (TMVB) for paleosecular variation analysis and stated that their work was the first systematic approach of that kind since 2005. This is incorrect, as Rodriguez-Trejo et al. (2019) published a much more comprehensive study, both in terms of the number of paleomagnetic data and their spatial extension within the TMVB, and this work was not even cited by Garcia et al. (2021). Additionally, Garcia et al. (2021) reported 11 allegedly new paleomagnetic directions from lava flows of monogenetic volcanoes and did not mention that 7 of these had been studied before by the same group (Maciel et al., 2014). Results are often similar, but in some cases dramatically different, now interpreted as being related to geomagnetic excursions or of different polarity. Such appalling differences between repeat studies of the same monogenetic volcano or lava flow must be declared, discussed, and in case of only minor differences statistical tests should be applied to check if such results could be combined into one direction. If such data are boldly different, they must be explained convincingly or otherwise resolved by additional sampling of the corresponding volcano. We also report numerous errors in the references, text, figures, and tables of that work.

Stratigraphy and eruptive history of the complex Puig de La Banya del Boc monogenetic volcano, Garrotxa Volcanic Field

The Puig de la Banya del Boc volcano is located in the southern sector of the Garrotxa Volcanic Field in the NE of the Iberian Peninsula and is part of the European Cenozoic Rift System. This monogenetic volcano was constructed on a hard basement of Paleozoic metamorphic rocks and shows a complex eruptive succession with phreatomagmatic, Strombolian, and effusive phases. Similar to other volcanoes of the same volcanic field, the succession of deposits of the Puig de la Banya del Boc volcano reveals the influence of the substrate, upon which the volcano forms, on eruption dynamics. In this case, the Paleozoic basement and its particular hydrodynamic properties controlled the way in which magma/water interactions occurred throughout the eruption. This volcano is coeval with the Clot de l'Omera, a small maar-type edifice that was emplaced on a conjugate fault, which belongs to the same fault system.

Study of Active and Fossil Hydrothermal Systems in Ijen Caldera Complex and Merubetiri Mountains, East Java

Ore deposits formed at subduction zone are associated with magmatism activities that are represented by volcanic activities at the surface. In the Eastern Sunda Arc, one of active volcanic activity can be found in Ijen Caldera Complex. The complex has hydrothermal volcanic manifestations with a very acidic pH. Meanwhile in the south of Ijen Complex, there is ancient volcanic complex called Merubetiri Mountains that is proven to be well-mineralized at Tumpangpitu as high sulfidation and porphyry-style mineralizations. An understanding of hydrothermal activity and volcanic landforms in active volcanic systems can be used as a powerful tool to understanding hydrothermal systems. This paper presents the distinction between active hydrothermal systems and fossil hydrothermal systems as an exploration’s tool in ancient volcanic systems. The method used in this study is remote sensing with focus on volcanic landforms, geological structures, and distribution of alteration minerals. ASTER satellite imagery, Landsat 8 satellite imagery, and DEMNAS are used in this study. ASTER and Landsat 8 images are processed with Principle Component Analysis (PCA) and Direct Principle Component (DPC) methods to determine the distribution of alteration minerals that are associated with propylithic, argillic, advanced argillic, and silisic alterations. Semi-quantitative method is used to identify geological structures by automatic lineament detection. Meanwhile, qualitative method is used by manual lineaments delineation on the DEM imagery. Delineations of volcanic landforms in active and ancient volcanic complex use semi-quantitative methods include ridge lineaments and flow pattern. Then, volcanic landform is manually delineated by determining the distribution pattern of ridges, flow pattern, morphological texture, and cross-cutting relationship of volcanic products as a key in determine the eruption centers. The results show a relationship between volcanic distribution and the main stresses in the Ijen Caldera Complex with NE-SW direction, which is represented by the elliptic and elongation of volcanic depression zone, monogenetic volcano, and intrusion distribution. Geological structures that are found in the Ijen Caldera Complex show E-W and NE-SW directions. Meanwhile, Merubetiri complex shows E-W, NW-SE, and N-S structural direction patterns. The distribution of alteration minerals associated with silisic, argillic, and advance argillic in the Ijen Caldera Complex are found in the central zone of stratovolcano, intra-caldera zone, and structural zone that intersects the caldera. This shows that active hydrothermal system is related to volcanic activity and geological structures. Meanwhile, in the Merubetiri complex, alteration minerals are associated with the eruption centers, diorite/granodiorite intrusions, and NW-SE strike slip fault. The understandings of volcanic setting and volcanic landforms are very important in the early stages of exploration to determine the prospect of mineral deposits related to hydrothermal system.

Geomorphological, morphometric, and spatial distribution analysis of the scoria cones in the Negros de Aras monogenetic volcanic field, northern Chile

The Negros de Aras monogenetic volcanic field in the Central Volcanic Zone of the Andes displays the highest concentration of scoria cones in northern Chile (0.23 per km2). It contains 66 vents, 22 of which are emission points of lava flows without an associated recognizable volcanic edifice, whereas 44 are typical scoria cones. Most vents are associated with basaltic andesite and andesite lava flows of up to 4.6 km in length. A few scoria cones show signs of either initial or final phreatomagmatic eruptions recorded in their pyroclastic successions. A geomorphological, morphometric, and spatial distribution analysis of the scoria cones of this volcanic field was carried out with the purpose of identifying the factors and processes that governed their emplacement, growth, and final morphology. The morphometric analysis was performed on 16 well-delimited scoria cones applying the MORVOLC algorithm using the TanDEM-X 12 m resolution digital elevation model. Analysis of the distribution and elongation of the craters of the scoria cones defines four alignments inferred to be related to the local and regional structural elements of the area. Volcanic activity seems to have been related to a N-S fault system with an E-W maximum stress orientation, favoring magma ascent and scoria cone emplacement following inherited fractures in these preferential orientations. The scoria cones show a wide range of morphologies and morphometries that can be related to different syn- and post-eruptive processes. Cones with large craters and high crater width / basal width ratios show clear evidence of phreatomagmatic eruptions (within their pyroclastic successions), whereas horseshoe-type cones are related to cone breaching or coeval lava flow effusion, and more pristine (i.e., relatively younger) cones are generally steeper.

Effusion rate estimation based on solidified lava flows: Implications for volcanic hazard assessment in the Negros de Aras monogenetic volcanic field, northern Chile

Effusion rate is the instantaneous lava flow output by a vent. It is one of the most important factors that govern the emplacement and dynamics of lava flows and can be determined by direct measurements or estimated through modeling. The Negros de Aras monogenetic volcanic field, located in the Central Volcanic Zone of the Andes, is the largest volcanic field in northern Chile. It is situated north of the active Socompa volcano and south of the Salar de Atacama basin, consisting of scoria cones and lava flows. Here, we estimate the effusion rates of three overlapping and representative solidified lava flows from this volcanic field applying an iterative procedure using the Q-LavHA GIS plugin, where the effusion rate is treated as an unknown parameter and the solution is reached by comparing the simulated results with the real extension of the flows. The pre-eruptive surface was reconstructed using the 12 m resolution TanDEM-X digital elevation model. Other required input parameters for the modeling (e.g., channel ratio, viscosity, temperature) were estimated through geomorphometric, petrographic, and geochemical analysis. The estimated effusion rates vary between 14 and 113 m3/s, comparable with rates measured elsewhere. The method was validated by applying it to two directly measured (Nyamuragira 2006; Mount Etna 2001) and one calculated effusion rate (Lentiscal 2450 BP, Canary Islands). The estimated effusion rates gave an average underestimation of 10%. Considering this percentage of adjustment, the effusion rates for the three studied lava flows from the Negros de Aras monogenetic volcanic field vary from 15 m3/s to 124 m3/s. Our results provide valuable information for mitigating volcanic risk in the event of future lava flow eruptions, which could affect nearby villages and mining operations.

The Quaternary monogenetic Bayuda Volcanic Field, Sudan – Insights into mantle and crustal processes during magma petrogenesis

The Holocene Bayuda Monogenetic Volcanic Field (BMVF) is located at the Great Bend of the river Nile in the north of Sudan. The analysed volcanic rocks are of basanitic to hawaiitic composition, characterising the BMVF as a sodic-alkaline volcanic field. Petrographic evidence documents olivine and clinopyroxene as the main fractionating phases as well as FC processes that were accompanied by assimilation of mantle and crustal rocks in addition to mingling and mixing processes. Utilising systematic differences in trace element variations, two primary magmas of Series A and B can be distinguished. Uniform normalised incompatible element patterns, e.g. LREE enrichment accompanied by HREE depletion, negative anomalies of K and Pb, and modelling based on partition coefficients of La, Dy and Yb in mantle residues, suggest partial melting of an amphibole-garnet lherzolite. The presence of amphibole provides a constraint, implying that the melt was derived from a metasomatised lithospheric mantle. The presence of the Pb-depletion (documented by Ce/Pb ratios of >30) suggests that all magmas are of HIMU-OIB type. This is supported by their uniform 87Sr/86Sr (0.703010–0.703347), 143Nd/144Nd (0.512869–0.512995), 206Pb/204Pb (19.787–19.895), 207Pb/204Pb (15.656–15.653) and 208Pb/204Pb (39.560–39.678) isotope characteristics. Additionally, we can describe the HIMU character of the NE African mantle with respect to 176Hf/177Hf (0.283006–0.283026). The mantle source of the BMVF magmas appears to have the composition of the common mantle “C” with an overprint by a HIMU component, resulting in higher radiogenic 206Pb/204Pb ratios above 19.5 (FOZO-HIMU-OIB type). We attribute this to the metasomatic character of the lithospheric mantle. The Hf/Nd isotope characteristics of the BMVF suggest that this metasomatism in the mantle source is most probably late Pan-African in age. When compared to circum-Mediterranean and regional volcanic fields, the high radiogenic Pb character of the BMVF indicates that their genesis cannot be related to magmatism associated with the activity of the Afar plume event and consequential magmatism along the Main Ethiopian Rift and the Red Sea Rift, as they are all of low radiogenic character.

Quaternary basaltic volcanic fields of the American Southwest

AbstractThe southwestern United States contains numerous monogenetic basaltic volcanoes distributed in intraplate volcanic fields. We review, on a regional scale, our current understanding of the Quaternary basalts with a focus on aspects pertinent to hazard assessment, such as physical volcanology and geochronology, while also summarizing the several petrogenetic conceptual models that have been proposed for the range of local tectonic settings in the region. We count 2229 volcanoes in 37 volcanic fields (including the Pinacate volcanic field, which is mostly in northern Sonora, Mexico). Volcanic landforms are dominantly scoria cones and ramparts with attendant lava fields that have a spectrum of ‘a'ā and blocky to pāhoehoe morphologies, while a small percentage of the volcanoes are maars and tuff cones. Explosive eruption styles that were driven mainly by magmatic volatiles, where they have been studied in detail, included Hawaiian, Strombolian, violent Strombolian, and sub-Plinian activity. The latter two have resulted in substantial fallout deposits that can be traced tens of kilometers from source vents. Phreatomagmatic styles have produced pyroclastic current (mainly pyroclastic surges), ballistic, and fallout deposits. These eruption styles pose hazards to humans when they occur in populated areas and to air travel and regional infrastructure even in sparsely populated areas. All but one of the major volcanic fields (fields that contain ∼100 or more Quaternary volcanoes) together form a northwest-southeast–trending band, which we suggest may reflect an influence of plate-boundary-related shearing on melt segregation in the upper mantle along with other factors; this view is consistent with recent global positioning system (GPS) and structural geologic data indicating the influence of dextral motion along the North America-Pacific plate boundary deep inside the Southwest. Of the 2229 Quaternary volcanoes identified, ∼548 (25%) have been dated, and only ∼15% have been dated with methods such as 40Ar/39Ar and cosmogenic surface exposure methods that are considered optimal for young basalts. Acknowledging the large uncertainty due to the poor geochronological data coverage, we use a simple Poisson model to provide a first-order estimate of recurrence rates of monogenetic volcanoes on the scale of the region as a whole; recurrence rates using our compiled age data set range from 3.74 × 10−4 yr−1 to 8.63 × 10−4 yr−1. These values are only based on dated and mapped volcanoes, respectively, and do not account for undated and buried volcanoes or other uncertainties in the volcano count. The time between monogenetic eruptions in the Southwest is similar to the repose times of some polygenetic volcanoes, which suggests that the regional hazard is potentially commensurate with the hazard from a reawakening stratovolcano such as those in the Cascade Range. Notable in our review is that only a few volcanoes have been the subject of physical volcanological characterization, interpretation, and detailed petrologic study that may elucidate factors such as magma generation, ascent (including time scales), and controls on eruption style.

The Risk Atlas of Mexico City, Mexico: a tool for decision-making and disaster prevention

We present a Risk Atlas of Mexico City based on a Geographical Information System (RA-GIS). We identified the prevalent social risk to the more relevant hazards in Mexico City (CDMX): earthquakes, volcanic eruptions, floods, landslides, forest fires, and land subsidence. A total of 274 shape-file maps were generated in this project. Seismic hazard was estimated for return periods (RP) of 20, 125, 250, and 475 years. Three areas in central and northwestern CDMX were identified along the Younger Chichinautzin Monogenetic Volcanic Field with a high probability of forming a new volcano. Subsidence is concentrated to the east and southeast of CDMX, where subsidence rates are among the highest worldwide. Flooding events were estimated for RP of 2, 5, 10, 50, and 100 years, and most of them are concentrated in the central and northern sectors of the city. During the dry season (December–April), southern CDMX has very high probability of forest fire occurrence. There is high susceptibility of landslides on the west and southwest of the city. The goals of this RA-GIS are to provide a tool to the local and federal authorities and all organizations responsible for disaster prevention and mitigation to: (1) improve the knowledge of the potential physical and social impact of local hazards; (2) provide elements for disaster prevention, mitigation, preparedness, and response; (3) benefit decision-makers with robust risk data; (4) provide information for land-use planning; and (5) support further research to reduce the impact of disasters caused by natural phenomena.

Pleistocene - Holocene volcanism at the Karkar geothermal prospect, Armenia

Quaternary volcanic centres north of the Bitlis-Zagros suture in Turkey, Iran and the Caucasus represent both volcanic hazards and potential or actual geothermal energy resources. Such challenges and opportunities cannot be fully quantified without understanding these volcanoes' petrogenesis, geochronology and magmatic, tectonic or other eruption triggers. In this preliminary study, we discuss the age and geology of the Karkar monogenetic volcanic field in Syunik, SE Armenia. The ~70 km 2 field is close to Armenia's only geothermal energy test drilling site. Fissure-fed trachybasaltic andesite to trachyandesite lavas erupted on a trans-tensional segment of the Syunik branch of the Pambak-Sevan-Syunik Fault, where previous studies suggested a Holocene age for the youngest eruptions. Here, high-resolution duplicate 40 Ar/ 39 Ar dating of 7 groundmass separates provided inverse isochron ages ranging from 7.4 ± 3.6 ka and 7.9 ± 2.9 ka to 353 ± 20 ka (2σ). Each lava flow displays petrographic and whole rock geochemical patterns consistent with melting of subduction-modified lithospheric mantle and extensive evolution within the crust involving fractional crystallisation and mixing of magma batches. Data confirm that volcanic activity related to the Syunik Fault overlapped with Palaeolithic to Bronze Age human occupation and remains a minor lava inundation hazard. Further geochemical work will allow constraint of the depth and timescales of magma storage. Both Karkar and the area around Porak volcano, which lies 35 km N of Karkar on the Syunik Fault, might be considered for future geothermal energy developments. • Monogenetic volcanism associated with the Syunik Fault, SE Armenian Uplands. • New 40 Ar/ 39 Ar data confirm last eruptions during the Holocene, consistent with 14 C and 3 He results. • Magmas sourced from sub-continental mantle lithosphere followed by fractionation and mixing. • Further identification of magma storage conditions will assist geothermal prospecting. • Volcanism still poses a hazard in this area and geophysical monitoring is recommended.

Implications of reworking processes on tephra distribution during volcanic eruptions: The case of Parícutin (1943–1952, western Mexico)

AbstractParícutin in western Mexico is considered one of the most studied monogenetic volcanoes worldwide. The volcano began its formation in the middle of a cornfield in February 1943 and lasted until March 1952. Descriptions of the eruption documented the remobilization of unconsolidated primary ashfall by rainfall and wind in minor proportions. Despite these descriptions, the resulting reworked deposits have not yet been described in stratigraphic sequence. We present the first stratigraphic study of interfingered primary pyroclastic and reworked deposits of Parícutin's succession. We identify 13 units, of which seven correspond to reworked deposits dispersed around the volcano. These deposits display sedimentary structures produced by tephra remobilization due to lahars and stream flows. In addition, some layers display dunes and ripples generated by dust storms. By using GIS tools, we integrated the existing data with our new composite stratigraphic column, the distribution map of the syn‐eruptive reworked deposits and a new isopach map. This new evaluation reveals that more than 70% of the total thicknesses around the volcano correspond to syn‐eruptive reworked deposits (R1–R4 units). Therefore, previous studies had overestimated the distribution of primary tephra from the Parícutin explosive phases. The lowest and flattest areas with wide rill networks, which are located 4–6 km north of the volcano, are composed of up to 90% reworked deposits. In contrast, proximal locations with gentler slopes located at medium altitudes better preserve pyroclastic deposits. This study brings new light to understanding the sedimentary processes that occur during volcanic eruptions and highlights the importance of recognizing pyroclastic and reworked deposits during monogenetic eruptions.

Modelling and simulation of a lava flow affecting a shore platform: a case study of Montaña de Aguarijo eruption, El Hierro (Canary Islands, Spain)

ABSTRACT Recent subaerial volcanism at El Hierro Island (Canary Islands, Spain) consists of monogenetic volcanic fields. This volcanism generated cinder cones, tephra air-fall deposits, and lava flows. The lava flows reach several kilometres in length extending through shore platforms and, sometimes, penetrating under the sea level. The volcanic landforms of El Hierro convert it into a natural laboratory for topographic and morphometric modelling and lava flow simulations. We perform the modelling and simulation of the Montaña de Aguarijo eruption, a cinder cone at the NE rift. The associated lava flow channelled through a V-shaped ravine until reaching a cliff, where formed cascades. The flow spread at the cliff base over a platform before reaching the sea modifying the coastline. Different maps were designed to show the results, including the geomorphologic reconstruction of the area affected by this eruption and the lava flow simulations obtained with the Q-LavHA plugin.

Translithospheric magma plumbing system of intraplate volcanoes as revealed by electrical resistivity imaging

AbstractThe magma plumbing systems of volcanoes in subduction and divergent tectonic settings are relatively well known, whereas those of intraplate volcanoes remain elusive; robust geophysical information on the magma pathways and storage zones is lacking. We inverted magnetotelluric data to image the magma plumbing system of an intraplate monogenetic volcanic field located above the stagnant Pacific slab in northeast China. We identified a complex, vertically aligned, low-resistivity anomaly system extending from the asthenosphere to the surface consisting of reservoirs with finger- to lens-like geometries. We show that magma forms as CO2-rich melts in a 150-km-deep asthenospheric plume crossing the whole lithosphere as hydrated melt, inducing underplating at 50 km depth, evolving in crustal reservoirs, and erupting along dikes. Intraplate volcanoes are characterized by low degrees of melting and low magma supply rates. Their plumbing systems have a geometry not so different from that of volcanoes in subduction settings.

Lithofacies and eruptive conditions of the southernmost volcanoes in the world (87\xb0 S)

Neogene volcanic centres are uncommon in the Transantarctic Mountains but at least three basaltic examples occur within 300 km of South Pole, above 2200 m asl and inland of the margin of the West Antarctic Rift System. They are the southernmost volcanoes on Earth and have yielded Early—mid Miocene isotopic ages. Two of the centres, at Mt Early and Sheridan Bluff, have been examined. The centre at Mt Early is unequivocally glaciovolcanic. It formed a tall monogenetic volcanic edifice at least 1 km high and > 1.5 km in diameter. It erupted under significantly thicker-than-modern ice, which was probably a fast-moving ice stream at the eruptive site and resulted in a distinctive constructive architecture and lithofacies. It is the first described example of a glaciovolcano erupted beneath an ice stream. The characteristics of the second centre at Sheridan Bluff indicate that it was also a monogenetic volcano but with a shield-like profile, originally c. 6 km in basal diameter but just c. 400 m high. It probably erupted in a substantial pluvial lake in an ice-poor or ice-free environment. The strongly contrasting eruptive settings now identified by the volcanic sequences at both centres examined testify to a highly dynamic Antarctic Ice Sheet during the Early—mid Miocene.

The magma source of small-scale intraplate monogenetic volcanic systems in northern New Zealand

The Auckland intraplate volcanic province consists of four small fields of basaltic monogenetic volcanoes. Each of these was active for a period of ~1 Myr and during the last 3 Myr the locus of magmatic activity migrated northward in discrete ~50 km steps. The most recent of these volcano fields is the Auckland Volcanic Field (AVF) in which individual eruptions have produced discrete magma batches within the composition range nephelinite to sub-alkaline basalt. This range of compositions is explained by partial melting involving variable melt/solid ratios together with modal heterogeneity in their mantle source. Eruptions in the field have been irregularly spaced during its 200 kyr life with repose periods varying between ≤0.1 and 13 kyr. Although most of Auckland's volcanoes represent a single period of eruption, paired eruption sequences in which smaller more alkaline magma batches have been followed by more voluminous less alkalic magmas have also occurred. A significant flare-up in activity at about 30 kyr produced compositionally discrete eruptions from at least five spatially separate locations all within a temporal interval of as little as 100 years. An interpretation of these data is that each event (volcano) in the AVF represents a discrete batch of magma extracted from an source with the capacity of producing a compositional variety of magma. Such a source forms when upwelling mantle undergoes adiabatic rise and exists as a metastable entity at the asthenosphere-lithosphere boundary for prolonged periods (105–106 years) during which time it is tapped to create individual magma batches. The shorter term magma extraction events that produced individual volcanoes in the AVF are suggested to be the result of crustal scale tectonic events. The behaviour of these four spatially separate monogenetic volcanic systems at temporal intervals of <106 years is likely linked to the long term tectonic evolution of the Pacific-Australian Plate boundary beneath the New Zealand region.

Tephrostratigraphy and Eruption History of Kozushima Volcano, Izu Islands, Central Japan during the Last 30,000 Years

Kozushima is a volcanic island, located in the northern part of the Izu Islands, approximately 170 km SSW of central Tokyo. The volcanism of Kozushima Volcano started at 80-60 ka and formed monogenetic volcanoes. The latest eruption occurred in AD 838, and was associated with the formation of the lava dome and pyroclastic cone of Tenjo-san. In order to contribute to the long-term forecasting of volcanic eruptions on the Izu Islands off Tokyo, the tephrostratigraphy and eruption history of Kozushima Volcano during the last 30,000 years is reconstructed. According to the geological surveys, the widespread Kikai-Akahoya (K-Ah; 7.3 cal ka) and Aira-Tanzawa (AT; 30.0 cal ka) tephras from southern Kyushu, and Niijima-Mukaiyama (Nj-My; AD 886), Niijima-Shikinejima (Nj-Sk; 8 cal ka) and Niijima-Miyatsukayama (Nj-Mt; 12.8 cal ka) tephras from the Niijima Volcano 20 km NNE of Kozushima are recognized. Tephras that also erupted from Kozushima Volcano are Kozushima-Tenjosan (Kz-Tj; AD 838), Kozushima-Ananoyama (Kz-An; 7-9 c), Kozushima-Chichibuyama-A′ (Kz-CbA′; 14-12.8 cal ka), Kozushima-Chichibuyama-A (Kz-CbA; 30-22 cal ka), and Kozushima-Chichibuyama-B (Kz-CbB; ca. 30 ka). Kz-An is formed by the activity of the northern volcanic chains (Kobe-yama–Anano-yama–Hanatate) just before the Tenjo-san eruption. Kz-CbA′ is distributed in southern Kozushima. Source vent and distribution of Kz-CbA′ have not yet been identified. The eruption history of Kozushima volcano over the last 30,000 years is as follows. At ca. 30 ka, Kz-CbB erupted in the central Kozushima, and the Nachi-san dome and Takodo-yama dome formed. At 30-22 ka, the Kz-CbA eruption in the southern Kozushima and the formation of the southern volcanic chain occurred. After the eruption of Kz-CbA′, the formation of the northern volcanic chain was followed by the eruption of Tenjo-san volcano. In addition, the eruption rate of Kozushima volcano is estimated during the last 30,000 years to be approximately 0.06 km3/1000 y in DRE.

Morphology and distribution of monogenetic volcanoes in Los Tuxtlas Volcanic Field, Veracruz, Mexico: implications for hazard assessment

Morphology and distribution of monogenetic volcanoes in Los Tuxtlas Volcanic Field, Veracruz, Mexico: implications for hazard assessment

Characteristics and implications of Albian volcanism in a magma-rich rift basin: Seismic volcano stratigraphic and geomorphological evidence from the Upper Suhongtu Member in the Chagan Sag, China-Mongolia border region

Buried volcanic successions imaged by 3D seismic data reveal facies components of Albian volcanism in the Chagan Sag of the Yingen-Ejinaqi Basin. The volcanic rocks of the Upper Suhongtu Member are composed mainly of vesicular and tight massive basalts and andesites. Three types of volcanoes, including monogenetic volcanoes, flood basalts, and shield volcanoes were recognized through detailed seismic facies analysis. A seismic geomorphological study showed that volcanism declined from Unit 1 to Unit 2, with the decline being strongly associated with the transition from the rift climax to the later syn-rift phase. In Unit 1, a center-type eruption arose at the onset, and was subsequently overwhelmed by multistage basaltic lavas supplied by fissure vents of the Maoxi, Tulage, and Barun faults in response to increased thermal fluid activity. Several cone- and crater-shaped monogenetic volcanoes formed by the center-type eruption that developed in Unit 2. In addition, a large shield volcano supplied by fissure vents and a major volcanic conduit developed in the northwestern part. The Albian volcanism of the Yingen-Ejinaqi Basin and the whole volcanic province contributed to a much hotter and more arid paleoclimate, and their records can be recognized from palynological and elemental geochemical evidence in the Chagan Sag and its surrounding area. Volcanism not only produced widely distributed strongly heterogeneous volcanic reservoirs but also accelerated the thermal maturation of source rocks, contributing to near-source hydrocarbon accumulation in Lower Cretaceous magmatic-rich rift basins of the East Asian region.

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.

Morphological and multivariate statistical analysis of quaternary monogenetic vents in the Central Anatolian Volcanic Province (Turkey): Implications for the volcano-tectonic evolution

The interaction and competition between magmatic and tectonic processes mostly control the spatial distribution and morphology of monogenetic volcanoes. The Central Anatolian Volcanic Province, situated in a strike-slip environment, provides a remarkable opportunity to understand this relationship. We defined six monogenetic clusters and analyzed 540 Quaternary monogenetic volcanoes in terms of morphological and spatial characteristics. There is no distinct correlation among the morphological parameters of scoria cones or lava domes, possibly owing to the various factors and the sporadic nature of magmatic activity in the region. Our detailed multivariate statistical and vent alignment analyses together with several implications in the literature reveal that the CAVP is a tectonically-controlled intraplate volcanic field, which is mostly driven by regional deformations. The presence of both clustered and non-clustered vent distributions and the petrological characteristics of the volcanics within the region indicates that the dikes are derived directly by the pre-existing melt-bearing heterogeneous mantle (i.e., Eğrikuyu monogenetic field) or the independent and short-lived shallow or deep crustal magma reservoirs (i.e., Nevşehir-Acıgöl volcanic field). The local changes in the stress regimes and crustal lithology result in variations of field shape, spatial vent distribution, and vent alignments throughout the region. The triggering mechanisms for the initiation of the Quaternary volcanism in the region can be the lithospheric-scale Central Anatolian fault zone, here considered as an immature rift zone where Erciyes volcanic field is developed and behaves as a possible magmatic transfer zone. Tuz Gölü fault zone as a western border of the so-called rift basin in the region is mostly responsible for the crustal propagation of magma, and the kinematic changes along this fault zone (i.e., strike-slip to normal) mostly shaped the spatial vent distributions and alignments of the clusters in its close proximity (e.g., Hasandağ-Keçiboyduran volcanic field).