Deep structure and origin of active volcanoes in China

We synthesize significant recent results on the deep structure and origin of the active volcanoes in China's Mainland. Magmatism in the western Pacific arc and back-arc areas is caused by dehydration of the subducting slab and by corner flow in the mantle wedge, whereas the intraplate magmatism in China has different origins. The active volcanoes in Northeast China （such as the Changbai and Wudalianchi） are caused by hot upwelling in the big mantle wedge （BMW） above the stagnant slab in the mantle transition zone and deep slab dehydration as well. The Tengchong volcano in Southwest China is caused by a similar process in the BMW above the subducting Burma microplate （or Indian plate）. The Hainan volcano in southernmost China is a hotspot fed by a lower-mantle plume which may be associated with the Pacific and Philippine Sea slabs＇ deep subduction in the east and the Indian slab＇s deep subduction in the west down to the lower mantle. The stagnant slab finally collapses down to the bottom of the mantle, which can trigger the upwelling of hot mantle materials from the lower mantle to the shallow mantle beneath the subducting slabs and may cause the slab-plume interactions.

Geochemistry and Tectonic Setting of Kohe Siahvolcanoes, North Qorveh, Sanandaj, Iran

The KoheSiah Volcanoes are located in the North of Qorveh city in the west of Iran. The KoheSiah volcanoes include several craters bearing domes located in the Kordestan Province, between latitudes 35°23'13.54” to 35°21'26.63”N and longitudes 47°54'38.26”E to 47°56'01.42”E. Based on the petrographic and geochemical analysis, the volcanic rocks in the KoheSiah area are classified as basalt, Alkali basalt, trachy-andesites and mugearite. The studied samples are alkaline with sodic to potasic feature based on Na2O/K2O ratios and belonging to Shoshonite series. Most of the alkaline volcanic rocks in the study area fall in the field of within in plate basalts (WPB) and represent of a mantle metasomatism trend associated with variable degrees in the partial melting of an enriched mantle source.

Seismic Signature Analysis for Clarification of Mud Volcanoes from the New Mud Diapirs Discovered at the NE-SW Moroccan Atlantic Margin

Our aim is to clarify mud volcanoes from the new mud diapirs resulting from the seismic attributes analysis applied to the low resolution Burmah oil “1973-1974” seismic data. The latter was carried out on the Larache and Tanger-Larache offshores from the NE-SW Atlantic margin. The high resolution seismic data was essential for this evaluation. In this case, we applied seismic signature analysis to four seismic profiles from the map of the seismic data set, which includes all new mud diapirs. This helped us to classify different types of mud diapirs within the seismic profiles. And as a result, six deep mud diapirs from the Prerifaine Nappe of Morocco, a shallow mud diapir, and four seafloor-piercing mud diapirs have been observed. Furthermore, the seafloor-piercing mud diapirs show a mushroom-shaped and conical-shaped cone. As they break through the seafloor, these kinds of cones characterize mud volcanoes. In this case, we may conclude that the resultant seafloor-piercing mud diapirs are likely to be mud volcanoes. However, more geological sampling and seafloor observation are still required.

Volcanoes

In the past thousand years,volcanoes have claimed more than 300,000 lives. Volcanology is ayoung and dangerous science that helps us against the power of the Earth itself.We live on a fiery planet. Nearly 2000 miles beneath our feet, the Earth's inner core reachestemperatures of 12,000 degrees Fahrenheit. Molten rock or magma, rises to the earth's surface. Acold, rigid crust fractured into some twenty plates. When magma breaks through crust it

Three-dimensional crustal movement and the activities of earthquakes,volcanoes and faults in Hainan Island,China

Hainan Island is a seismic active region, where Qiongshan M7.5 earthquake occurred in 1605 and several seismic belts appeared in recent years, especially the NS trending seismic belt （NSB） located in the northeast part of the island. Here is also a magmatic active region. The lava from about 100 volcanoes covered more than 4000 km^2. The latest eruptions occurred on Ma＇anling-Lei Huling volcanoes within 10,000 years. The neotectonic movement has been determined by geological method in the island and its adjacent areas. In the paper, the present-day 3D crustal movement is obtained by using Global Positioning System （GPS） data observed from 2009 to 2014 and leveling observations measured in 1970s and 1990s respectively. The results show the horizontal movement is mainly along SEE direction relative to the Eurasian Plate. The velocities are between 4.01 and 6.70 mm/a. The tension rate near the NSB is less than I mm/a. The vertical movement shows the island uplifts as a whole with respect to the reference benchmark Xiuyinggang. The average uplifting rate is 2.4 mm/a. The rates are 2-3 mm/a in the northwest and 3-5mm/a in the northwest. It shows the deformation pattern of the southwest island is upward relative to the northeast, which is different from the result inferred from the coastal change and GPS. Haikou and its adjacent region present a subsidence in a long time. The southern part of the middle segment of the Wangwu-Wenjiao fault uplifts relative to the northern. Meanwhile, the western part uplifts relative to the eastern NSB. The vertical crustal motion and the two normal faults nearly correspond to the terrain. The NSB is located along the Puqiangang-Dazhibo fault, which is assessed as a segmented fault with a dip of 80°-90° and party exposed. The 3D deformations and other studies reveal the present activities of earthquakes, volcanoes and the faults. The small earthquakes will still occur in the NS belt and the volcanoes are not active now.

Baossi–Warack monogenetic volcanoes, Adamawa Plateau,Cameroon: petrography, mineralogy and geochemistry

Three monogenetic cones in the Baossi–Warack area, Ngaoundéré, Adamawa Plateau forming part of the Cameroon Volcanic Line(CVL) are documented in this study. Basaltic lavas(<1 km^3) scattered around these vents and restricted volcaniclastic deposits were emplaced by Hawaiian and mild strombolian style eruptions. The lavas are porphyritic, mainly composed of olivine(chrysolite) and clinopyroxene(diopside and augite) phenocrysts and plagioclase(andesine) microphenocrysts. Accessory minerals include titano-magnetite and titano-hematite, nepheline,apatite and amphibole xenocrysts. Sanidine occurs in some samples and sodi-potassic albite in others. Some olivines and clinopyroxenes exhibit resorbed margins and thin reaction rims while plagioclase displays oscillatory zoning, and sieved textures as a result of magma mixing. Whole-rock geochemistry data indicates that the lavas are silica-undersaturated, composed of basanites and basalts, showing little compositional variations(SiO_2: 39.20 wt.%–48.01 wt.%,MgO: 5.29 wt.%–9.70 wt.%). Trace elements patterns of these lavas suggest they are enriched in LILE including Pb,probably due to crustal contamination. REE patterns suggest cogenetic magmas below Baossi 1 and Baossi 2 volcanoes,and distinct sources below Warack volcano and nearby lavas.The lavas studied show affinity to high-μ(HIMU), enriched type Ⅰ(EM1) and Oceanic Island Basalt(OIB)-like mantle signatures and thus indicate a heterogeneous mantle source underneath the vents as noted at other monogenetic and polygenetic volcanoes along the CVL. Primary melts derived from low degrees of partial melting(0.5%–2%) and encountered low rates of fractionation, and crustal contamination coupled with magma mixing. These melts evolved independently through structural weaknesses in the basement.

FEASIBLE STUDY ON THE INTEGRATION SYSTEM FOR THE SPACE MONITORING OF MAJOR EARTHQUAKES AND VOLCANOES IN TERRESTRIAL LAND

With the rapid development of space technology,earth observation tech nology and sky observatory technolo-gy,they have played a more and more im portant part in monitoring and predi cting of earthquakes and volcanoes i n the terres-trial land.In recent years,the rela ted agencies have done the experimen ts and researches on monitoring and p redicting of earthquakes and volcanoes in the forewarning period by means of many appr oaches,such as satellite thermal in frared re-mote sensing(TIRS),Global Positioning System(GPS),differential interferometric syn thesis aperture radar(D-INSAR),astronomical time-latitude residual anomaly,and Geographic Information Systems (GIS),etc.A quite large number of re-search foundation has been built in t he fundamental theories and applica tion methods.The experiments and re searches have shown that these technology is e fficient methods for high frequency crust movement.If the existed separate scientific forces and results are possibly asse mbled together to form a more complete integration monitoring system wit h the combina-tion of space,sky observation,grou nd,deep geology and macro anomaly,i t will come into a new stage of monitoring and predicting of earthquakes and volca nic eruptions.

Deep geodynamics of far field interconti- nental back-arc extension: Formation of Cenozoic volcanoes in northeastern China

There are three cases of variation of trench location possible to occur during subduction: trench fixed, trench ad- vancing, and trench retreating. Retreat of trench may lead to back-arc extension. The Pacific plate subducts at low angle beneath the Eurasia plate, tomographic results indicate that the subducted Pacific slab does not penetrate the 670 km discontinuity, instead, it is lying flat above the interface. The flattening occurred about 28 Ma ago. Geo- dynamic computation suggests: when the frontier of the subducted slab reaches the phase boundary of lower and upper mantle, it may be hindered and turn flat lying above the boundary, facilitates the retreat of trench and back-arc extension. Volcanism in northeastern China is likely a product of such retreat of subduction, far field back-arc extension, and melting due to reduce of pressure while mantle upwelling.

Mud volcanoes in the South Caspian basin: Nature and estimated depth of its products

In paper based on the results of previous studies and latest investigations of mud volcanoes in the South Caspian basin the depth occurrence of fluid, mud and rocks are calculated and modeled. Major factors causing formation of diapirism/mud volcanism in the South Caspian basin are Pliocene-Quaternary high sedimentation rates (up to 3 km/my), super thick sedimentary cover (up to 25-30 km), predominance of clayey rocks (reaching 80%) in the section, low temperatures (with 15℃-18℃/km gradient), overpressures reaching lithostatic, the onset of petroleum generation lowered to considerable depths. The majority of the mud volcanoes are associated with the petroleum bearing structures. Depths where the liquid, gaseous and solid products of mud volcanoes are sourced appear to be different. The gases have the deepest roots (7-15 km) which are the main force in formation and activity of MVs. Source of the fluidized clayey mass does not lie below 3-4 km. Oils emitted by mud volcanoes are the product of destruction of petroleum accumulations occurring beneath them.

Yanshan, Gaoshan-Two Active Volcanoes of the Volcanic Cluster in Arshan, Inner Mongolia

The volcanic cluster in Arshan, inner Mongolia, is located in the west of the middle section of the Da Hinggan Mountains. There are more than forty Cenozoic volcanoes among which the Yanshan Volcano and Gaoshan Volcano are the active ones in broad sense and basaltic central vents. Arshan is a newly found volcanic active region in the Chinese continent. The volcanoes are perfectly preserved and composed of cinder cones, pyroclastic sheets and lava flows. Their cones are grand and the Gaoshan cone is about 362m high, and the depth of the Yanshan crater is about 140m. The pyroclastic sheet is mainly made up of scoria, and the distribution area of scoria with thickness more than i m is about 27km^2 . There are two Carbonized-wood sites in the pyroclastic sheet and the ^14C datings indicate ages of 1990±100a B. P and 1900 ±70a B. P, which are rectified by dendrodating. Basaltic lava flows are uncovered, and they change from pahoehoe in the early stage to aa in the later stage. There are lots of perfect fumarolic cones, fumarolic dishes and lava tumulus in the front zones. The spread of lava flow is controlled by the local topography and its main body flowed northwestwards covering the Holocene rivers and swamp deposits and blocked up the Halahahe river and its branches to create six lava-dam lakes. For these distinguishing features, Arshan volcanic cluster could be called another natural “Volcano Museum”.

Combustion Metamorphic Rocks as a Sign of Ancient Mud Volcanoes

Zones of combustion metamorphism(CM)are frequently associated with oil fields and adjacent bituminous marine sediments.A typical example is the Mottled Zone(MZ)complexes located within carbonate strata at the western margin of the Arabian petroleum province(Israel,Jordan).Being localized upon the eroded surface of Upper Cretaceous stratum, the MZ complexes are composed of brecciated sediments of the underlying Cretaceous sequence uplifted from depths of at least 1.5 km.They

Towards a Volumetric Variation of Lake Kivu Gases by the Nyamulagira and Nyiragongo Volcanoes

After the volcanic eruption of January 17th, 2002, Goma Volcano Observatory (OVG) initiated carbon dioxide (CO2) monitoring in the fractures south of the Nyiragongo volcano and at the northern edge of Lake Kivu. During the period from March 17th, 2017 to June 10th, 2020, twice a week, a GA 5000 gasometer was used for CO2 in the fractures as well as in the mazukus, respectively, as part of a project funded by the Kingdom of the Netherlands through the Lake Kivu Monitoring Program (LKMP) in Rwanda. The level of volcanic activity was determined by the volume of gas emitted by the volcano and measured by a DOAS and the seismicity measured by a network of 15 seismometers managed by the OVG. The results show that the concentration of CO2 in the active fractures from recent Nyiragongo eruptions varies with volcanic activity and the occurrence of a large earthquake in the East African Rift;but in the mazukus there is almost no relationship between CO2 content and volcanic activity. The study also shows that the influence of carbon dioxide in mazukus on the carbon dioxide into the Lake Kivu waters remains a major research question. The purpose of this study is to establish the relationship between the existing Carbon Dioxide (mazukus) in the Northern watershed and that of the deep waters of Lake Kivu.

Geophysical evidence of a large occurrence of mud volcanoes associated with gas plumbing system in the Ross Sea(Antarctica)

Seafloor and buried reliefs occur along continental margin of the Ross Sea(Antarctica).These features are several kilometres wide and tens of metres high,exhibiting cone or flat-top dome shapes.Previous studies have proposed a volcanic or glacial origin for these formations,but these hypotheses do not account for all the available evidence.In this study,we use morpho-bathymetric data,intermediate resolution multichannel seismic and high resolution chirp profiles,as well as magnetic lines to investigate these clusters of mounds.By employing targeted processing techniques to enhance the geophysical characterization of the seafloor and buried reliefs,and to understand the underlying geological features,we propose that the reliefs are mud volcanoes.Some of these formations appear to be associated with a plumbing system,as indicated by acoustic anomalies linked to sediment containing gas.These formations are likely fed by clayey source rocks of Miocene age.Additionally,other reliefs might be the result of mud mobilisation caused by gravity instability and fluid overpressure.

Deep origin of Cenozoic volcanoes in Northeast China revealed by 3-D electrical structure

The three-dimensional(3-D)electrical structure of the upper-mantle was used to examine the deep origins of and relationship among the Cenozoic volcanoes located in Northeast China(NEC).High-quality,long-period magnetotelluric(LMT)full-impedance tensor data were collected in NEC and subjected to 3-D Gauss-Newton inversion in order to construct a resistivity model.The resulting model reveals the presence of multiple localized low-resistivity anomalies(LRAs)within the high resistivity lithosphere beneath NEC.These LRAs partially coincide with Cenozoic volcanoes on the surface.Three LRAs that form a larger,annular LRA were observed in the deep upper mantle beneath the Songliao Basin,whereas vein-like LRAs were found in the asthenosphere that connect the lithosphere and deep upper mantle.Petrophysical analyses suggest that the LRAs may have been caused by fluid-induced melting.Based on our electrical model,we propose that,following dehydration of the subducted Western Pacific slab into the mantle transition zone(MTZ)beneath NEC,the released water migrated upward and caused partial melting at the top of the MTZ beneath the Songliao Basin.Under the effect of buoyancy,the melted mantle formed a thermal upwelling that caused melting of asthenosphere before diapiring at the base of the dry lithosphere.The magma then penetrated structural boundaries(such as thinner,weaker,or activated suture zones)and finally reached the Earth's surface.This melting and upwelling of hot mantle materials may have resulted in large-scale volcanism in the region throughout the Cenozoic,including the eruption of Changbai Mountain and Halaha Volcanoes.Our results suggest that the Cenozoic NEC volcanoes may all share a similar mode of genesis,and probably originated from the annular LRA in the deep upper mantle.

Shuttle imaging radar-C (SIR-C) detection for the Cenozoic volcanoes in West Kunlun, China

THE technique of imaging radar remote sensing is one of the most important means for earth observation in the 1990s. Imaging radar, transmitting electromagnetic wave from its sideways, is very sensitive to the surface roughness and, to a large extent, can accentuate the terrain information and explicitly depict the details of surface features. Therefore, it is

Volcanoes

Here are some of the most asked questions about volcanoes. frequently What are volcanoes?A volcano is a mountain or hill with an opening through which steam gases and lava from the centre of the Earth can escape into the air.

Volcanoes to Cool Climate?

全球变暖问题的日益严重促使各国科学家们绞尽脑汁思考对策。有人想到了火山爆发时喷发出的遮天蔽日的火山灰,提议仿效此法来遮蔽日光,从而使地球"降温"。然而立刻有科学家提出,想通过遮挡日光照射到地球的方法不仅不会产生什么效果,还会迅速减少空气中水分子的含量,从而导致严重的旱灾。

Geochemical characteristics of natural gas from mud volcanoes in the southern Junggar Basin

A number of mud volcanoes exist in the southern Junggar Basin. To date few systematic studies on natural gas geochemistry of mud volcanoes have been conducted in China. In June 1991 and August 2010, the authors investigated the mud volcanoes in the southern Junggar Basin twice, and the mud volcanism weakened gradually as seen from the variations such as the decrease of gas pressure and output, the downthrow and dry up of the mud pool. The volcanic intensity was significantly weaker than that in Taiwan. The natural gas from the mud volcanoes in the southern Junggar Basin has similar geochemical characteristics, indicating the same source or origin. The main component of the mud volcano gas is alkane gas with contents of 91.15%-97.49%, and the gas is high-quality commercial gas since methane dominates in the alkane. The 513C1 values are -49.1‰-0.6‰, which are in accordance with the peak δ3C1 frequency of mud volcano gas around the world, and the alkane gas displays positive carbon isotopic series, i.e., δ3C1〈δ3C2〈δ13C3, suggesting typical thermogenic origin. The helium in the mud volcano gas is typically crust-derived due to the low R/Ra values of 0.011-0.054. The mud volcano gas is coal-derived since the δ13C2 values are all greater than -28‰, and C1/C1-4 and δ13C1 values are in accordance with those of natural gas derived from the Lower-Middle Jurassic coal-measures. Therefore, alkane gas from mud volcanoes in the southern Junggar Basin is mainly sourced from the Lower-Middle Jurassic coal-measures.

Temporal and environmental factors drive community structure and function of methanotrophs in volcanic forest soils

Methanotrophs,organisms that obtain oxygen by oxidizing methane,are recognized as the only known biological sink for atmospheric CH_4,and forest soil methanotrophs play crucial roles in mitigating global warming.The succession patterns of methanotrophic communities and functions in Wudalianchi volcano forest soils could provide a basis for the study of evolutionary mechanisms between soil microorganisms,the environment,and carbon cycling of temperate forest ecosystems under climate change.In this study,the characteristics and drivers of methanotrophic community structure and function of two volcanic soils at different stages of development are analyzed,including an old volcano and a new volcano,which most recently erupted 300 years and 17-19×10^(5)years ago,respectively,and a non-volcano hills as control,based on space for time substitution and Miseq sequencing and bioinformation technology.The results showed that CH_(4) fluxes were significantly higher in old-stage volcano forest soils than new-stage forest soils and non-volcano forest soils.There were significant differences in the community composition and diversity of soil methanotrophs from different volcano forest soils.Methylococcus was the dominant genus in all soil samples.Additionally,the relative abundance of Methylococcus,along with Clonothrix,Methyloglobulus,Methylomagum,Methylomonas and Methylosarcina,were the important genera responsible for the differences in methanotrophic community structure in different volcano forest soils.The relative abundance of methanotroph belonging toγ-proteobacteria was significantly higher than that belonging toα-proteobacteria(P<0.05).Chao1,Shannon and Simpson indices of soil methanotrophic community were significantly lower in new-stage volcanos and were significantly affected by bulk density,total porosity,p H,nitrate,dissolved organic carbon and dissolved organic nitrogen.There were significant differences in community structure between new-stage and old-stage volcanoes.Bulk density and p H are important soil properties contributing to the divergence of methanotrophs community structure,and changes in soil properties due to soil development time are important factors driving differences in methanotrophs communities in Wudalianchi volcanic soils.

A Set of Three Technologies Will Save Mankind from Climate Change in the Most Inexpensive Way Possible

This paper formulates a set of three technologies that should deal with the greatest threat to mankind—climate change at the lowest cost.The main technology will be“Sunny Rain”.It considers technology to prevent eruptions of submarine volcanoes at shallow depths and technologies that provide scalable and impactful solutions to reduce carbon emissions across diverse industries as complementary technologies used to reduce cost.A list of submarine volcanoes at shallow depths that are likely to spew waterborne dust into the atmosphere has begun to be created.If the governments of Japan,Italy,and Greece,which have submarine volcanoes at shallow depths(Kiki,Marsili,Columbo),prevent eruptions of these volcanoes,it will provide electricity to these countries,save many of their citizens from death,and save humanity from the greatest threat—climate change—in the most inexpensive way possible!