The Applicability and Productiveness of a Systematic Literature Review Methodology in Volcanology Research: Case of the Magma Pathway at the Mount Cameroon Volcano

The presented research illustrates the applicability and productiveness of the systematic literature review methodology, a non-empirical methodology in the geological sciences, particularly volcanology. The systematic literature review methodology is a replicable, rigorous, and transparent methodology for synthesizing existing literature to answer questions on a specific topic. The synthesis allows for knowledge consolidation, such as identifying knowledge gaps. In our illustration of this methodology, we focused on the expanding knowledge about the magma pathway at Mount Cameroon, one of Africa’s active volcanoes. Our synthesis of the relevant international geoscience research literature is based on the framework of knowledge about the magma pathway beneath a typical basaltic volcano. The framework has three primary components: magma supply, storage, and transport to erupting vents. Across these components is a total of twelve secondary components. The result is a previously non-existent and fragmented overall understanding of the magma pathway at Mount Cameroon. The gaps in the understanding (such as in the magma supply rates, timescales of chamber processes, and magma ascent rates) may be addressed in future research. Another key implication of the presented research lies in the proof of concept of the systematic literature review methodology as an applicable qualitative research methodology in the study of volcanoes.

Detection of a mud volcano in the Weitan Banks area of the northern South China Sea

Situated between the petroliferous Cenozoic Zhujiang(Pearl)River Mouth Basin and the mud volcano-rich Mesozoic Dongsha Basin in the middle sector of the northern South China Sea,the Weitan Banks area has been previously mapped as a basement high that is composed of Mesozoic magmatic rocks.In this study,we present several favorable indicators for petroleum geology that were detected from geophysical profiling and benthic sampling in the area.A conspicuous hill was discovered,named“Zhongwei Hill”,~80 m high above the~340 m deep seafloor and~1 km broad,in a depression with more than 7 km thick sedimentary strata.The Zhongwei Hill was seismically imaged with a mushroom-shaped structure and containing a cake-like crown,fluid flow pipes,and an~10 km broad anticline at depth.Thus,the hill represents a source-plumbing-eruption system.Shallow gas zones linked to deep fracture were found at or near the hill.Stratigraphic correlation indicates that the deep strata comprise the Jurassic and Paleogene strata,the major hosts of hydrocarbon source rocks.In addition to the hill,there are number of mounds from which three bottom water samples were collected and the samples are rich in dissolved methane with concentrations high up to~900 nmol/L,much higher than the background level(0.5–2 nmol/L).The benthic samples are rich in coarse sediment clastics,authigenic carbonate nodules,and deep-water habitats likely feeding on methanotrophic community.Given these observations and the context,we propose that the Zhongwei Hill represents a mud volcano,likely thermally driven,that seeps methane from Jurassic and Paleogene source layers,thus poses a favorable clue for significant hydrocarbon generation capacity in transitional zone of the Zhujiang River Mouth Basin and the Dongsha Basin.

The formation of explosive volcanos at the circum-Pacific convergent margin during the last century

The circum-Pacific convergent margin is known as"the Ring of Fire",with abundant volcano eruptions.Large eruptions are rare but very disastrous.It remains obscure how are large explosive volcanos formed and where are the danger zones.Three largest eruptions since 1900,the Hunga Tonga-Hunga Ha’apai,the Mt.Pinatubo,and the Novarupta were found to be associated with subductions of volatile-rich sediments and located close to slab windows.Among them,the Hunga Tonga-Hunga Ha’apai is close to subducting seamount chains;the Mt.Pinatubo is right next to subducting fossil ridges.Both seamount chains and fossil ridges have water depths much shallower than the carbonate compensation depths(CCD)in the Pacific Ocean.Seismic image shows that a seamount is subducting towards the Novarupta volcano.Subduction of volatile-rich sediments and a slab window nearby are the two most important favorable conditions for catastrophic eruptions.Slab windows expose the mantle wedge to the hot asthenosphere,which increases the temperature and dramatically promotes the partial melting of the carbonate-fluxed domains,forming volatile-rich magmas that powered explosive eruptions.

A Seismic Facies Analysis to Determine the Relative Age and History of the Al Idrissi Mud Volcano from Offshore Larache Located in the NW Moroccan Atlantic Margin

Formed on top of the Gulf of Cadiz, the Al Idrissi mud volcano is the shallowest and largest mud volcano in the El Arraiche mud volcano field of the northwestern Moroccan margin. The development and morphology of mud volcanoes from the El Arraiche mud volcanoes group have been studied at a large scale. However, the time interval related to their formation period still needs to be better understood. In this regard, we interpreted and analyzed the seismic facies from the 2D reflection data of the GEOMARGEN-1 campaign, which took place in 2011. The aim was to identify the seismic sequences and draw the Al Idrissi mud volcano system to determine the formation period of the Al Idriss mud volcano. And as a result, the Al Idrissi mud volcano system is made of both buried and superficial bicone and was identified along with the Upper Tortonian to Messinian-Upper Pliocene facies. As the initial mud volcano extrusive edifice, the buried bicone was formed in the Late-Messinian to Early-Pliocene period. However, the superficial bicone, as the final extrusive edifice, was included in the Late Pliocene. In this case, the timing interval between the buried and superficial bicone is equivalent to the Late-Messinian to Upper-Pliocene period. Therefore, the latter corresponds to the Al Idrissi mud volcano formation period.

Earthquake, Volcano and Earth Rotation Harmonics

Earthquake prediction is considered impossible for there is no scientific way to find the date and time, the location, and the magnitude of an earthquake. A new idea is introduced in this paper—earth rotation harmonics triggered natural volcano and earthquake. With earth rotation harmonics response model for a location, it could be possible to calculate the earthquake date and time, and the magnitude. Properties of earth rotation harmonics triggered earthquake are discussed and verified with earthquake data from USGS website. Also, both earth tide and ocean tide effects on earthquake are discussed and verified with earthquake data—tides did not trigger the natural earthquake, they only affect the earthquake activities and time.

Studies on the Extraction Methods of Metagenomic DNA from Mud Volcano in Xinjiang

[Objective]To seek one effective extraction method of metagenomic DNA from mud volcano.[Method]The metagenomic DNA from mud volcano was extracted by CTAB extraction method,SDS-enzyme method,improved method,reagent kit method.The extraction of four kinds of methods were compared.[Result]The extracted rate in reagent sets method was the highest,next was improved method,the extracted quantity in SDS-enzyme method was maximum.DNA extracted by the improved method was diluted ten times for PCR.[Conclusion]Considering economy and purity,the improved method can be used as one effective extraction method of metagenomic DNA from mud volcano.

Volcano video data characterized and classified using computer vision and machine learning algorithms

Video cameras are common at volcano observatories,but their utility is often limited during periods of crisis due to the large data volume from continuous acquisition and time requirements for manual analysis.For cameras to serve as effective monitoring tools,video frames must be synthesized into relevant time series signals and further analyzed to classify and characterize observable activity.In this study,we use computer vision and machine learning algorithms to identify periods of volcanic activity and quantify plume rise velocities from video observations.Data were collected at Villarrica Volcano,Chile from two visible band cameras located^17 km from the vent that recorded at 0.1 and 30 frames per second between February and April 2015.Over these two months,Villarrica exhibited a diverse range of eruptive activity,including a paroxysmal eruption on 3 March.Prior to and after the eruption,activity included nighttime incandescence,dark and light emissions,inactivity,and periods of cloud cover.We quantify the color and spatial extent of plume emissions using a blob detection algorithm,whose outputs are fed into a trained artificial neural network that categorizes the observable activity into five classes.Activity shifts from primarily nighttime incandescence to ash emissions following the 3 March paroxysm,which likely relates to the reemergence of the buried lava lake.Time periods exhibiting plume emissions are further analyzed using a row and column projection algorithm that identifies plume onsets and calculates apparent plume horizontal and vertical rise velocities.Plume onsets are episodic,occurring with an average period of^50 s and suggests a puffing style of degassing,which is commonly observed at Villarrica.However,the lack of clear acoustic transients in the accompanying infrasound record suggests puffing may be controlled by atmospheric effects rather than a degassing regime at the vent.Methods presented here offer a generalized toolset for volcano monitors to classify and track emission statistics at a variety of volcanoes to better monitor periods of unrest and ultimately forecast major eruptions.

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”.

A Potential Flood Hazard Caused by Tianchi Volcano Eruption in Changbai Mountain, Northeast China

Geohazards appear to be increasing in frequency globally. It is of necessity to actively manage these natural hazards to minimize loss of life and property. From an early warning perspective, this paper stresses the potential fatal flood hazard represented by the huge volume of water in Tianchi Lake, the unique geography of Changbai Mountain, and the limited flood control ability in the upstream of the Songhua River. Northeast Asian countries should keep a watchful eye on the Changbai volcano cooperatively, and Chinese government especially needs to prepare plans for fighting a flood in advance.

Volcanology and Archaeology for Better Understanding the History of Campi Flegrei: Post-NYT Bradyseisms and More Rapid Deformation

The Campi Flegrei volcanic district includes insular (Ischia and Procida Islands) and peninsular volcanic activity (Campi Flegrei volcanic field) with the link to older activity till Ponza Island. The history of this area has been studied in detail since the eruption of the Campanian Ignimbrite (CI, age: 39 ky BP, volume: 200 - 300 km3), which makes this one of the most powerful eruptions in Europe. In the Neapolitan Yellow Tuff (NYT: age: 15.0 ky BP, volume: 50 km3), another powerful eruption occurred. Activity younger than the NYT can be subdivided in three epochs which include 70 recognized ephemeral eruptions. The volume of these individual eruptions is between 0.4 and 1 km3 (DRE). Probably, the long-lasting magma reservoirs (i.e., CI and NYT) represent eruptions that are fed by deep magma reservoirs. In deep reservoirs (>10 km), magmas stagnate, differentiate and are probably modified by crustal components (Hercynian basement). The long-lasting reservoirs are also the ones that feed the ephemeral shallow magmatic system (2 - 5 km) that gave rise to the post-caldera magmatic epochs. However, the magmas of the post-caldera epochs are isotopically heterogeneous and made by several components (i.e., least evolved (as an example the Minopoli eruption, 9500 y BP), CI, and NYT components). Mixing between ephemeral shallow reservoirs occurs. Mixing of long lasting reservoirs also occurs;and also during explosive eruptions. The concentration of earthquakes and the deformation history suggest that Campi Flegrei could erupt again with an ephemeral eruption, especially if the uplift will reach 5 - 6 m like Monte Nuovo eruption, given existing uplift of 1970-72 and 1983-84.

Evolution History of Gassan Volcano, Northeast Japan Arc

Evolution history of the volcano is essential not only to characterize the volcano, but also consider magma genesis beneath the volcano. Most of the stratovolcanoes in northeast Japan follow a general evolutional course: cone building, horse-shoe shaped caldera forming collapse, and post-caldera stages. However, the detailed history of each stage is not well investigated. We investigated evolution history of young edifice of Gassan volcano, representative stratovolcano in rear side of northeast Japan arc. Most of the products are lavas, which are divided into two groups by geomorphologic and geologic features. The former (Gassan lower lavas) is composed of relatively thin and fluidal lavas, whose original geomorphology remains a little, while the latter (Gassan upper lavas) is composed of relatively thick and viscous lavas, whose original geomorphology is moderately preserved. Based on geologic features, the upper lavas can be further divided into Gassan upper north lavas and upper summit lavas in ascending order. After the formation of the thick lavas, horse-shoe shaped caldera was formed by the instability of the edifice, probably triggered by fault activity. No evidence of post caldera activity inner part of it is observed. Based on K-Ar data, estimated age of Gassan lower lavas is ca. 0.75 to ca. 0.6 Ma, those of Gassan upper north and upper summit lavas are ca. 0.60 to ca. 0.55 Ma and ca. 0.55 to ca. 0.45 Ma. The eruption rate is estimated to be ca. 0.0004 km3/1000 years in Gassan lower lavas and ca. 0.02 km3/1000 years in Gassan upper summit lavas. These values are lower than the eruption rate of representative Japanese stratovolcanoes.

Field Geological Exploration of the Ashikule Volcano Group in Western Kunlun Mountains

From May 4 to May 30, 2011, a field exploration of the Ashikule basin in the Western Kunlun Mountains area was conducted by a research team from the Institute of Geology, China Earthquake Administration and Earthquake Administration of Xinjiang Uygur Autonomous Region. This work is financially supported by the special fund for China earthquake research project "The Comprehensive Scientific Exploration of the MS7.3 Yutian Earthquake in 2008 and the Ashikule Volcano Group". Through detailed field survey on geological and geomorphological features of the Ashikule volcano group, which is one of the highest altitude volcanic plateaus (about 5000m) in the world, we have determined the total number of volcanoes, the eruption type and structural parameters, and approximate active history of the volcano group. Our studies have provided field evidence for resolving past controversies such as the authenticity of the news report about the eruption event on May 27, 1951, the eruption pattern of the Daheishan volcano, and the reality of the Gaotaishan volcano.

Volcanic Debris-avalanche Deposits of the Laoheishan Volcano and Huoshaoshan Volcano in Wudalianchi

Large amounts of volcanic debris-avalanche deposits, which take the shape of hummocks, are distributed around the peripheries of the Laoheishan volcano and Huoshaoshan volcano in Wudalianchi World Geopark. In earlier times, they were called "satellite volcanoes", namely, freestanding volcanoes. This paper points out that these deposits actually came from the collapse of the cones of these two volcanoes. When the lava flow spilled out at the base of the slope of the cones, the slope broke up and collapsed under the action of gravity. Later, ravines were formed on the slope. Caved slope clastics, accompanying lava flow, accumulated at the rims of the volcano cones. Although some accumulations may form very large cones, they are not volcanoes, but deposits of volcanic debris avalanches.

A Preliminary Study of the Types of Volcanic Earthquakes and Volcanic Activity at the Changbaishan Tianchi Volcano

Since 2002, a significant increase in seismicity, obvious ground deformation and geochemical anomalies have been observed in the Changbaishan Tianchi volcanic area. A series felt earthquakes occur near the caldera, causing great influence to society. In this paper, the types of volcanic earthquakes recorded by the temporal seismic network since 2002 have been classified by analyzing the spectrum, time-frequency characteristics and seismic waveforms at different stations. The risk of volcano eruptions was also estimated. Our results show that almost all earthquakes occurring in Tianchi volcano are volcanic-tectonic earthquakes. The low frequency seismic waveforms observed at a few stations may be caused by local mediums, and have no relation with long-period events. Although the level of seismicity increased obviously and earthquake swarms occurred more frequently than before, we considered that the magma activity is still in its early stage and the eruption risk of Changbaishan Tianchi volcano is still low in the near future.

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.

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.

Behavior of Siderophile and Chalcophile Elements in the Subcontinental Lithospheric Mantle beneath the Changbaishan Volcano,NE China

The mantle xenoliths in the Quaternary ChangbaishanVolcano in southern Jilin Province contain spinel-facies lherzolites. The equilibration temperatures for these samples range from 902℃ to 1064℃ based on the two-pyroxene thermometer of Brey and Kohler （1990）, and using the oxybarometry of Nell and Wood （1991）, the oxidation state was estimated from FMQ-1.32 to -0.38 with an average value of FMQ-0.81 （n = 8）, which is comparable to that of abyssal peridotites and the asthenospheric mantle. ThefO2 values of peridotites, together with their bulk rock compositions （e.g., Mg#, Al2O3, CaO, Ni, Co, Cr） and mineral compositions （e.g., Mg# of olivine and pyroxene, Cr# [=Cr/ [Cr＋Al]] and Mg# [=Mg/[Mg＋Fe2~] of spinel）, suggest that the present-day subcontinental lithospheric mantle （SCLM） beneath the Changbaishan Volcano most likely formed from an upwelling asthenosphere at some time after the late Mesozoic and has undergone a low degree of partial melting. The studied lherzolite xenoliths show low concentrations of S, Cu, and platinum group elements （PGE）, which plot a flat pattern on primitive-mantle normalized diagram. Very low concentrations in our samples suggest that PGEs occur as alloys or hosted by silicate and oxide minerals. The compositions of the studied samples are similar to those of peridotite xenoliths in the Longgang volcanic field （LVF） in their mineralogy and bulk rock compositions including the abundance of chalcophile and siderophile elements. However, they are distinctly different from those of peridotite xenoliths in other areas of the North China Craton （NCC） in terms of Cu, S and PGE. Our data suggest that the SCLM underlying the northeastern part of the NCC may represent a distinct unit of the newly formed lithospberic mantle.

S-wave velocity structure beneath Changbaishan volcano inferred from receiver function

The S wave velocity structure in Changbaishan volcanic region was obtained from teleseismic receiver function modeling. The results show that there exist distinct low velocity layers in crust in volcano area. Beneath WQD station near to the Tianchi caldera the low velocity layer at 8 km depth is 20 km thick with the lowest S-wave velocity about 2.2 km/s At EDO station located 50 km north of Tianchi caldera, no obvious crustal low velocity layer is detected. In the volcanic region, the thickness of crustal low velocity layer is greater and the lowest velocity is more obvious with the distance shorter to the caldera. It indicates the existence of the high temperature material or magma reservoir in crust near the Tianchi caldera. The receiver functions and inversion result from different back azimuths at CBS permanent seismic station show that the thickness of near surface low velocity layer and Moho depth change with directions. The near surface low velocity layer is obviously thicker in south direction. The Moho depth shows slight uplifting in the direction of the caldera located. We con- sider that the special near surface velocity structure is the main cause of relatively lower prominent frequency of volcanic earthquake waveforms recorded by CBS station. The slight uplifting of Moho beneath Tianchi caldera indicates there is a material exchanging channel between upper mantle and magma reservoir in crust.

Study of Distal Pyroclastic-flow Stratum from Tianchi Volcano in 1215(±15) Eruption:Pyroclastic-flow Over Water

In this paper, we describe three strata at the distal part of the pyroclastic-flow from the Tianchi volcano in 1215 （±15） eruption. One of the strata with crosslayers that are different from typical pyroclastic-flow strata may come from a ground-surge. The grain-size and scanning electron microscopy （SEM） analysis was performed to study the origin of the pyroclastic-flow. Characteristics of grain-size distribution show that it is similar with the ash cloud. Through the SEM analyses, we found some quench structures with less damage on the surfaces of the vitric pumices. These phenomena indicate that there has been hydration in the transportation processes at the distal of pyroclastic-flow. It has partly changed the transportation mechanism of pyroclastic-flow, which transitions form dense flow to diluted flow. This paper develops a new distal pyroclastic-flow model in the Tianchi volcano that can be divided into three stages, i.e. the quench stage, expanding stage and depositing stage.

Magmatic Processes of Ashi Volcano, Western Kunlun Mountains, China

The Ashikule volcanic cluster （AVC） in western Kunlun Mountains is located in a graben region at the convergence of the Altun and Kangxiwa fault zones,and consists of more than 10 main volcanoes and dozens of volcanelloes.The Ashi volcano lies in the central part of the volcanic cluster.The lithology,chemical composition and texture of Ashi volcanic rocks were studied in detail,and their implication in magmatic processes was discussed.The phenocrysts in Ashi volcanic rocks consist mainly of plagioclase and pyroxene,and the statistical results of phenocryst contents show that the rocks can be subdivided into two groups.In group A,the content of pyroxene phenocrysts is generally higher than that of plagioclase phenocrysts,but an inverse relation occurs in group B.In TAS diagram,the compositions of both groups fall into the trachyandensite field,but they are obviously concentrated into two clusters.The two clusters exist also in the oxide diagrams.The pyroxene phenocrysts comprise augite,bronzite and hypersthene,and their Mg# histogram shows two peaks.Plagioclase phenocrysts with reaction rim are observed in rocks of both groups.The An values of the core are generally 30-40,and those of the rim are 44-48,which are closer to those of euhedral plagioclases.The bronzites are in equilibrium with the melt,and two sets of magma depths,i.e.,18-25 km and 13-18 km,can be estimated by using thermobarometer proposed by Putirka.The hypersthenes are not in equilibrium with the melt,and can be assigned to xenocrysts.The crystal size distribution （CSD） curves of plagioclase appear as kinked lines indicative of magma mixing.The above analyses show that two magma pockets might exist beneath the Ashi volcano.It is likely that they are connected with each other.The one has more evolved and contains more acidic magma,and the other is a trachyandensite magma pocket characterized by layering.The magma from the upper part of the trachyandensite magma pocket might mix with more acidic magma,resulting in a magma that is more acidic than the magma from the lower part.