Stage Of Eruption Research Articles

Significant Release of Dissolved Inorganic Nutrients From the Shallow Submarine Volcano Tagoro (Canary Islands) Based on Seven-Year Monitoring

Tagoro, the shallow submarine volcano that erupted south of El Hierro (Canary Islands, Spain) in October 2011, has been intensely monitored for over 7 years, from the early eruptive stage to the current degassing stage characterized by moderate hydrothermal activity. Here, we present a detailed study of the emissions of inorganic macronutrients (NO2-+NO3-, PO4, and Si(OH)4) comprising a dataset of over 3300 samples collected through three different sampling methodologies. Our results show a significant nutrient enrichment throughout the whole studied period, up to 8.8-fold (nitrate), 4.0-fold (phosphate) and 16.3-fold (silicate) in the water column, and larger enrichments of phosphate (10.5-fold) and silicate (325.4-fold), but not of nitrate, in the samples collected directly from the vents. We also provide some preliminary results showing ammonium (NH4+) concentrations up to 1.97 µM in the vent fluids as compared to 0.02 µM in the surrounding waters. Nutrient fluxes from the volcano during the degassing stage were estimated as 3.19 ± 1.17 mol m-2 yr-1 (NO2-+NO3-), 0.02 ± 0.01 mol m-2 yr-1 (PO4), and 0.60 ± 1.35 mol m-2 yr-1 (Si(OH)4), comparable to other important nutrient sources in the region such as fluxes from the NW-African upwelling. Nutrient ratios were affected, with a minimum (NO3-+NO2-):PO4 ratio of 2.36:1; moreover, a linear correlation between silicate and temperature allowed to use this nutrient as a mixing tracer. This study is bound to shed light on how shallow hydrothermal systems impact the nutrient-poor upper waters of the ocean.

Correlation between skeletal development and maxillary canine eruption.

The aim of this study was to find a correlation between the permanent maxillary canine eruption and the cervical vertebral maturation index (CVMI). 145 subjects (73 male and 72 female) in the age of 7-14 years were examined radiographically with lateral cephalographs and orthopantomographs. The CVM patterns were evaluated on the lateral cephalograph using the classification of Hassel and Farman. The stage of the permanent maxillary canine eruption has been investigated on the orthopantomographs depending on its vertical height in relation to the adjacent incisor. Descriptive statistics were obtained for both CVMI stages and canine eruption grading. Spearman rank correlation test was used to determine the correlation between both methods. The minimum level of significance was considered less than 0.05 (P < 0.05). Results showed a strong correlation between CVMI and the grading of the maxillary canine eruption in both female and male and the (r) value estimated was 0.862 and 0.758, respectively. Over 90% of deceleration stage of CVMI in both genders show canine eruption (pubertal growth spurt) about 91.66% for female and 95.65% for male and a small percentage of delay eruption 8.33% and 4.35% in female and male gender, respectively, with a predilection to the female gender. A significant correlation between the permanent maxillary canine eruption stages and skeletal maturity was found. The eruption of maxillary canine occurs before the end of pubertal growth. Any delay in the eruption of maxillary canine after the deceleration stage of CVMI, suggesting a chance of impaction.

Epidemiological rationale for community-based programs of caries prevention of permanent teeth for children of Samara city

The global objectives of WHO in the field of oral health by 2020 include the average intensity of caries among 12-year-old children no more than 1.5 by the DMFT index. In Samara the value of the DMFT among the adolescents at age 12 is 3.5. To identify the appropriate timing for a launching of community-based schemes of dental caries prevention of permanent teeth for children of Samara. In a cross-sectoral multisample research from March to May 2017, the time of eruption and intensity of caries of the first permanent molars among children in Samara were studied. A total of 405 children aged 5 to 8, attending preschool and school educational institutions were examined. The quantity and the stage of eruption of the first permanent molars were assessed; the initial and manifest forms of caries were considered during the calculation of indexes of caries intensity of teeth and surfaces. One to four first permanent molars were erupted among 26.3% of children aged 5, at an average 0.6±0.14 per one surveyed, the prevalence of caries of the first permanent molars was equal to 1.3%, including 1.3% of the initial carious defeats. In 6-year-old children - 65% had the first permanent molars, at an average of 2.38±0.199, and the prevalence of caries in these teeth was 29.63%, including initial forms of caries 27.16%. The results among 7-year-old children - 87.18% and 3.12±0.156, 60.3% and 51.28%, respectively. In 8-year-old children these figures were equal: 97.26%, 3.79±0.091, 68.49% and 60.27%, respectively. The rate of eruption of the first permanent molars and the prevalence of their carious lesions among girls was significantly higher than among boys. The optimal age of children of Samara for inclusion in the regional programs of dental caries prevention is the age of 4 years - the age of the beginning of the first permanent molar eruption.

Fingerprinting the Late Pleistocene tephras of Ciomadul volcano, eastern–central Europe

ABSTRACTLate Pleistocene tephras derived by large explosive volcanic eruptions are widespread in the Mediterranean and surrounding areas. They are important isochronous markers in stratigraphic sections and therefore it is important to constrain their sources. We report here tephrochronology results using multiple criteria to characterize the volcanic products of the Late Pleistocene Ciomadul volcano in eastern–central Europe. This dacitic volcano had an explosive eruption stage between 57 and 30 ka. The specific petrological character (ash texture, occurrence of plagioclase and amphibole phenocrysts and their compositions), the high‐K calc‐alkaline major element composition and particularly the distinct trace element characteristics provide a strong fingerprint of the Ciomadul volcano. This can be used for correlating tephra and cryptotephra occurrences within this timeframe. Remarkably, during this period several volcanic eruptions produced tephras with similar glass major element composition. However, they differ from Ciomadul tephras by glass trace element abundances, ratios of strongly incompatible trace elements and their mineral cargo that serve as discrimination tools. We used (U‐Th)/He zircon dates combined with U‐Th in situ rim dates along with luminescence and radiocarbon dating to constrain the age of the explosive eruptions of Ciomadul that yielded distal tephra layers but lack of identified proximal deposits.

The Structure of Solar Coronal Mass Ejections in the Extreme-ultraviolet Passbands

Abstract So far, most studies on the structure of coronal mass ejections (CMEs) are conducted through white-light coronagraphs, demonstrating that about one third of CMEs exhibit the typical three-part structure in the high corona (e.g., beyond 2 ), i.e., the bright front, the dark cavity, and the bright core. In this paper, we address the CME structure in the low corona (e.g., below 1.3 ) through extreme-ultraviolet (EUV) passbands and find that the three-part CMEs in the white-light images can possess a similar three-part appearance in the EUV images, i.e., a leading edge, a low-density zone, and a filament or hot channel. The analyses identify that the leading edge and the filament or hot channel in the EUV passbands evolve into the front and the core later within several solar radii in the white-light passbands, respectively. What is more, we find that the CMEs without an obvious cavity in the white-light images can also exhibit the clear three-part appearance in the EUV images, which means that the low-density zone in the EUV images (observed as the cavity in white-light images) can be compressed and/or transformed gradually by the expansion of the bright core and/or the reconnection of the magnetic field surrounding the core during the CME propagation outward. Our study suggests that more CMEs can possess the clear three-part structure in their early eruption stage. The nature of the low-density zone between the leading edge and the filament or hot channel is discussed.

New Insights of Geomorphologic and Lithologic Features on Wudalianchi Volcanoes in the Northeastern China from the ASTER Multispectral Data

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imaging system onboard NASA’s (National Aeronautics and Space Administration’s) Terra satellite is capable of measuring multispectral reflectance of the earth’s surface targets in visible and infrared (VNIR) to shortwave infrared (SWIR) (until 2006) as well as multispectral thermal infrared (TIR) regions. ASTER VNIR stereo imaging technique can provide high-resolution digital elevation models (DEMs) data. The DEMs data, three-dimensional (3D) perspective, and ratio images produced from the ASTER multispectral data are employed to analyze the geomorphologic and lithologic features of Wudalianchi volcanoes in the northeastern China. Our results indicate that the 14 major conical volcanic craters of Wudalianchi volcanoes are arranged as three sub-parallel zones, extending in a NE (Northeast) direction, which is similar to the direction of regional fault system based on the ASTER DEMs data. Among the 14 volcanic craters in Wudalianchi, the Laoheishan, and Huoshaoshan lavas flows, after the historic eruptions, pouring down from the crater, partially blocked the Baihe River, which forms the Five Large Connected Pools, known as the Wudalianchi Lake. Lithologic mapping shows that ASTER multispectral ratio imagery, particularly, the Lava Flow Index (LFI) (LFI = B10/B12) imagery, can clearly distinguish different lava flow units, and at least four stages of volcanic eruptions are revealed in the Wudalianchi Quaternary volcano cluster. Thus, ASTER multispectral TIR data can be used to determine relative dating of Quaternary volcanoes in the semi-arid region. Moreover, ASTER 3D perspective image can present an excellent view for tracking the flow directions of different lavas of Wudalianchi Holocene volcanoes.

Risk and reward: Explosive eruptions and obsidian lithic resource at Nabro volcano (Eritrea)

Despite abundant Pleistocene calderas in the East African Rift and Afar, and the significance of regional tephra horizons for archaeological and paleoenvironmental dating, the entanglements of volcanoes and their eruptions with human behaviour and paleoecology have received little attention. Here, we focus on the intertwined human and eruptive history at Nabro, a caldera-topped volcanic massif close to the Red Sea littoral of Eritrea. Nabro exemplifies the antagonism of opportunities and threats posed by a large silicic volcano, active at least since the Middle Pleistocene and as recently as 2011. Using argon isotopic measurements, we establish the first chronology of key eruptive stages of Nabro and neighbouring Mallahle, revealing a history of explosive and effusive volcanism in the Middle and Late Pleistocene. Past eruptions were an important source of obsidian that was exchanged over long distances across land and sea during the Neolithic. We infer that the availability of high-quality obsidian, combined with Nabro’s favourable microclimate and proximity to the Red Sea coast, likely attracted humans to this volcanic landmark since the later Middle Pleistocene. Drawing on observations of the immediate consequences of the 2011 eruption on landscape and local pastoralist communities, we consider also the impacts of past volcanic cataclysms on human populations. In addition to the threat to life, explosive eruptions of Nabro circa 130 ka and 62 ka ago would have abruptly curtailed procurement of its obsidian resource. Our findings suggest further attention be paid to evaluating the significance of East African volcanic landscapes, eruptions and resources for understanding human behaviour in deep antiquity.

The timing and compositional evolution of volcanism within northern Harrat Rahat, Kingdom of Saudi Arabia

AbstractHarrat Rahat, one of several large, basalt-dominated volcanic fields in western Saudi Arabia, is a prime example of continental, intraplate volcanism. Excellent exposure makes this an outstanding site to investigate changing volcanic flux and composition through time. We present 93 40Ar/39Ar ages and six 36Cl surface-exposure ages for volcanic deposits throughout northern Harrat Rahat that, when integrated with a new geologic map, define 12 eruptive stages. Exposed volcanic deposits in the study area erupted &amp;lt;1.2 Ma, and 214 of 234 eruptions occurred &amp;lt;570 ka. Two eruptions occurred in the Holocene, including a historically described basalt eruption in 1256 C.E. and a trachyte eruption newly recognized as Holocene (4.2 ± 5.2 ka). An estimated ∼82 km3 (dense rock equivalent) of volcanic product have erupted since 1.2 Ma, though this is a lower limit due to concealment of deposits &amp;gt;570 ka. Over the past 570 k.y., the average eruption rate was 0.14 km3/k.y., but volcanism was episodic with periods alternating between low (0.04–0.06 km3/k.y.) and high (0.1–0.3 km3/k.y.) effusion rates. Before 180 ka, eruptions vented from the volcanic field’s dominant eastern vent axis and from a subsidiary, diffuse, western vent axis. After 180 ka, volcanism focused along the eastern vent axis, and the composition of volcanism varied systematically along its length from basalt dominated in the north to trachyte dominated in the south. We hypothesize that these compositional variations &amp;lt;180 ka reflect the growth of a mafic intrusive complex beneath the southern portion of the vent axis, which led to the development of evolved magmas.

Two-stage modeling of Strombolian-type eruptions and quantification of the model parameters: Insight from the seismic and acoustic signals

The seismic signals of majority Strombolian explosions show a two-phase structure that may be the result of a two-stage explosive eruption. We quantify the parameters of two proposed stages of Strombolian eruptions at volcanoes Arenal, Aso and Yasur using 193 seismic records and 18 acoustic signals and considering that the first stage of eruption represents the seismically active process of the gas slug expansion and ascent (GSEA) in the conduit and the second stage is associated with the gas slug burst at the surface. It is shown that the radiated seismic energy of Strombolian explosions at volcanoes is strongly dependent on the seismic energy radiated during GSEA. The seismic energy of explosions is correlated also with the duration of GSEA process in the interval of durations between 1.3 and 3.7 s. For shorter GSEA durations, the correlation is absent. The acoustic energy of explosions is characterized by inverse dependence on the durations of GSEA. These results demonstrate the influence of the GSEA process on the surface manifestations of Strombolian explosions.

Contact dermatitis: A great imitator

Contact dermatitis (CD) refers to a group of cutaneous diseases caused by contact with allergens or irritants. It is characterized by different stages of an eczematous eruption and has the ability to mimic a wide variety of dermatologic conditions, including inflammatory dermatitis, infectious conditions, cutaneous lymphoma, drug eruptions, and nutritional deficiencies. Irritant CD and allergic CD are the two main presentations of the disease. The diagnosis is based on a detailed history, physical examination, and patch testing, if necessary. Knowing the conditions mimicked by CD should improve the accuracy of the diagnosis. Avoiding the causative substances and taking preventive measures are necessary for the treatment.

Diagnostic performance of eruption stages for identification of skeletal maturity.

Objectives:To investigated the diagnostic performance of circumpubertal eruption stages which identify skeletal maturity stages using the cervical vertebral maturation (CVM) method in a Saudi population.Methods:This is a retrospective cross-sectional study. Lateral cephalograms, panoramic radiographs, and intraoral pictures of 600 orthodontic patients (284 boys, 316 girls) who met inclusion criteria were assessed. Records were retrieved between January 2016 and April 2018. The diagnostic performance of eruption stages for identifying skeletal maturity was tested with positive likelihood ratios (LHR+).Results:Prevalence of each CVM stage in the eruption stages was reported. For every eruption stage, LHR+ was reported in order to identify every CVM stage. The majority of the LHR+ values were ≤3.5, with a significant value of ≥10 for the identification of the post-pubertal growth stage. The other eruptions stages did not strongly predict skeletal maturity.Conclusion:In treatment planning for cases that require identifying the growth peak, the use of eruption stages is not recommended as an indicator of skeletal maturity except for the early permanent dentition stage where strong diagnostic performance for identifying post-pubertal skeletal growth stage has been shown.

Facies architecture of a subaqueous volcano–sedimentary succession on Bogda Mountains, NW China—Evidence of extension in Late Carboniferous

A Late Carboniferous volcano–sedimentary complex outcrops on the southwestern flank of the Bogda Mountains, NW China. The volcanic architecture, spatial relationships, and emplacement mechanisms of the lithofacies were studied in detail, providing a lithofacies context for previously published structural and geochemical studies and constraining the reconstruction of palaeo‐environments. Four distinct volcano–sedimentary facies are identified in the Qijiagou Formation: close‐packed pillow basalts, pillow basalts with interstitial sediments, hyaloclastites, and peperites. Textural features of the lithofacies, especially hyaloclastites and peperites, provide clear evidence for in situ fragmentation of lava flows, co‐volcanic sedimentation of limestone, and intimate interaction between lava, water, and sediments. They demonstrate autochthonous, subaqueous origin of the succession. Discovery of peperites and stratigraphic transitions of the related lithofacies indicate a progressively deepening subaqueous environment, resembling a volcanic evolution from early stage of eruption at a shallower level to increasingly subsiding basin with increasing eruption frequency of basaltic lava at greater water depth. Vesicularity of basalts, ambient pressure, and peperitic features indicate eruption depth at between 1,500 and 2,500 m. The deep extensional basin in the Baiyanggou area was coeval with bimodal volcanism, uplift, and granite intrusion along strike in the region, all indicating continental collision and post‐collisional extension. The substantial depth of the Baiyanggou Basin indicates that it may have been a back‐arc or even a residual oceanic basin.

Normative Data of Variables Determining Eruption of Third Molars in Orthodontic Patients – A Retrospective Study

Objectives: 1) To Formulate a normative data of variables affecting the eruption of third molar. 2) To help format a research data to compare variable changes occurring during formative and eruption stage (11-16 years)of third molar. Materials and Methods: The sample comprised of Orthodontic patients at CMCH from 2012-2019, within an age group of 11years -16 years, which was approved by the ethical committee. 40 Male and 40 Female Patient's Orthopentogram with complete set of teeth were considered in the study. The measurements analysed were: 1) Retromolar space:is distal contact of PMM2(Permanent mandibular second molar) and junction of occlusal plane to the anterior border of the mandible. 2) Gonial Angle: angle between the tangent from inferior border of the mandible and posterior border of the mandible. 3) Mesiodistal width of second molar : greatest distance between mesial and distal portion of the crown. 4) Mesiodistal width of third molar: greatest distance between mesial and distal extension of the crown. 5) Angulation of first and second Molar : the angle formed between the long axis of PMM1 (Permanent mandibular first molar) and PMM2 (Angulation m1m2). 6) Angulation of second molar to base of Mandible: the angle formed between the long long axis of PMM2 and the tangent drawn to the inferior border of the mandible (Angulation m2bm). 7) Nolla's classification of third Molar. Trophy Dicom; carestream LS 8000c machine programmed with Kodak software was used to record the digital OPG with standard protocol and head position. The 7 Variables were analysed with the Kodak software and the measurements were recorded on excel worksheet. Results: The Data was used for comparison of all variables to explore gender specific differences, only the mesiodistal width was significantly different between the gender. A descriptive table was formulated with a range of measurements for all variables. A correlation between Retromolar space and all other variables was analysed ,there is a positive correlation with formation of third molar(Nolla's grading) and retromolar space in females and it is statistically significant. Though a weak ,correlation exists between other variable and retromolar space ,it was not statistically significant. Conclusion: 1) A normative data and Data for future research, of variables affecting the eruption of third molar in their formative and eruptive stage was Formulated. 2) Though a weak correlation exists between other variable and retromolar space during the formative and eruption stage of third molars.

Advanced Applications of Synthetic Aperture Radar (SAR) Remote Sensing for Detecting Pre- and Syn-eruption Signatures at Mount Sinabung, North Sumatra, Indonesia

DOI:10.17014/ijog.6.2.123-140Mount Sinabung was re-activated at August 28th, 2010 after a long repose interval. The early stage of a phreatic eruption was then followed by magmatic eruptions at September 15th, 2013 for years until now. To understand the ground surface changes accompanying the eruption periods, comprehensive analyses of surface and subsurface data are necessary, especially the condition in pre- and syn-eruption periods. This study is raised to identify ground surface and topographical changes before, intra, and after the eruption periods by analyzing the temporal signature of surface roughness, moisture, and deformation derived from Synthetic Aperture Radar (SAR) data. The time series of SAR backscattering intensity were analyzed prior to and after the early eruption periods to know the lateral ground surface changes including estimated lava dome roughness and surface moisture. Meanwhile, the atmospherically corrected Differential Interferometric SAR (D-InSAR) method was also applied to know the vertical topographical changes prior to the eruptions. The atmospheric correction based on modified Referenced Linear Correlation (mRLC) was applied to each D-InSAR pair to exclude the atmospheric phase delay from the deformation signal. The changes of surface moistures on syn-eruptions were estimated by calculating dielectric constant from SAR polarimetric mode following Dubois model. Twenty-one Phased Array type L-band SAR (PALSAR) data on board Advanced Land Observing Satellite (ALOS) and nine Sentinel-1A SAR data were used in this study with the acquisition date between February 2006 and February 2017. For D-InSAR purposes, the ALOS PALSAR data were paired to generate twenty interferograms. Based on the D-InSAR deformation, three times inflation-deflation periods were observed prior to the early eruption at August 28th 2010. The first and second inflation-deflation periods at the end of 2008 and middle 2009 presented migration of magma batches and dike generations in the deep reservoir. The third inflation-deflation periods in the middle of 2010 served as a precursor signal presenting magma feeding to the shallow reservoir. The summit was inflated about 1.4 cm and followed by the eruptions. The deflation of about 2.3 cm indicated the release pressure and temperature in the shallow reservoir after the early eruption at August 28th, 2010. The last inflation-deflation period was also confirmed by the increase of the lava dome roughness size from 5,121 m2 on July to 6,584 m2 on August. The summit then inflated again about 1.1 cm after the first eruption and followed by unrest periods presented by lava dome growth and destruction at September 15th, 2013. The volcanic products including lava and pyroclastics strongly affected the moisture of surface layer. The volcanic products were observed to reduce the surface moisture within syn-eruption periods. The hot materials are presumed responsible for the evaporation of the surface moisture as well.

Lahar deposits generated after the Millennium eruption of the Changbaishan Tianchi volcano in the Erdaobaihe River system, China

After the Plinian Millennium Eruption (including the ME-I and ME-II eruptive stages) of Changbaishan Tianchi volcano in 969 ± 20 CE, two large-volume lahars were deposited mainly on the northern flank of the Erdaobaihe River, which flows through the only outlet from Tianchi Lake: (1) a lahar deposit containing gray and black pumice (Lahar (G&B) P) and (2) a lahar deposit containing lithic particles (Lahar L). Based on the sedimentary characteristics of lahar outcrops and grain-size and compositional analyses performed using standard dry sieving techniques, examination of thin sections and geochemical analyses, the origins, transport and deposit processes and fluid phase variations of the two lahar deposits are studied. These two lahar deposits are fan-like in the flat medial area (23–60 km from the crater) and fill channels in the distal mountainous area (>60 km from the crater). Lahar L in the medial area represents a complete composite lahar flow deposit with a frontal debris head (very coarse gravel texture, extremely poor sorting, massive and matrix-supported structure) and a hyperconcentrated fluid phase body and tail (coarse sandy texture, very poor sorting, faint horizontal stratification with thin lenses of gravel, clast-supported structure). Lahar L in the distal area represents the material that passed the debris flow head, and the fluid phase changes from debris flow to hyperconcentrated (poor sorting, clear thin horizontal stratification) downcurrent. The fluid phase of Lahar (G&B) P changes from debris flow in the medial area (medium gravel to fine sand, very poor sorting, thick horizontal stratification with floating pumice on each unit surface) to hyperconcentrated flow (poor sorting, thin horizontal stratification, clear normal graded bedding) and to stream flow (moderate sorting, cross-bedding) in the distal area. Lahar (G&B) P was likely formed by the mixing of water from Tianchi Lake and pyroclastic flows of ME-II. Lahar L was likely triggered by a sudden release (dam break) from Tianchi Lake. An assessment of the risk posed to the stability of Tianchi Lake is as important as an assessment of the eruption risk.

The First Results of Tephrochronological Study of Late Pleistocene–Holocene Volcanic Eruptions in the Zhom–Bolok River Valley (Eastern Sayan)

The first results of tephrochronological studies of Late Pleistocene–Holocene volcanic eruptions in the Zhom-Bolok River valley (Eastern Sayan) are reported. Based on the analysis of bottom sediments of the glacial lake Kaskadnoe-1, a detailed chronological scale of volcanic activity in this region has been worked out. It is established that the eruptions began at least 14 300 years ago and continued, gradually weakening, to 6280 years ago. In this period, ten groups of peaks of sediment enrichment in microtephra are registered for Kaskadnoe-1 Lake. The average interval between the stages of eruptions in this period was ~500–600 years. Between 14 300 and 13 400 years ago, the most large-scale volcanic events took place, eruptions were practically not interrupted, and the explosive activity was the most intense. The volcanic activity in the region in the period between 6280 and 2000 years ago is characterized by a relative rest. Later, eruptions resumed reaching peak values 1150 years ago and completing 800 years ago.

Clinical evaluation of short term space variation following premature loss of primary second molar, at early permanent dentition stage

PurposeThe present study aimed at determining whether the premature loss of a deciduous second molar results in a clinically relevant loss of space and arch length reduction. MethodsSplit mouth evaluation of approximately 32 patients at early permanent dentition stage with unilateral premature loss of the deciduous second molar either in the upper arch or the lower arch. The contra lateral side with no tooth loss served as controls. Dental models and radiographs were obtained. The space in the extraction site and control sides were measured and analyzed for space loss and eruption stage of premolars in three weeks time frame. Results and conclusionThe mean combined space before second primary molar extraction was 25.04 mm (±4.25), while the average space post extraction was 24.61 (±4.27) and the difference was found to be statistically significant (P < 0.01). Furthermore, neither subject’s age, nor successor premolar eruption stage were found to be correlated significantly with the amount of space loss (P-values 0.989 and 0.811, respectively). Space loss after premature extraction of second primary molar in three weeks time frame was statistically significant thereby emphasizing the use of space maintainers at the earliest.

Topological model of the anemone microflares in the solar chromosphere

Context. The chromospheric anemone microflares, which were discovered by Hinode satellite about a decade ago, are specific transient phenomena starting from a few luminous ribbons on the chromospheric surface and followed by an eruption upward. While the eruptive stage was studied in sufficient detail, a quantitative theory of formation of the initial multi-ribbon structure remains undeveloped until now. Aims. We construct a sufficiently simple but general model of the magnetic field sources that is able to reproduce all the observed types of luminous ribbons by varying only a single parameter. Methods. As a working tool, we employed the Gorbachev–Kel’ner–Somov–Shvarts (GKSS) model of the magnetic field, which was originally suggested about three decades ago to explain fast ignition of the magnetic reconnection over considerable spatial scales by tiny displacements of the magnetic sources. Quite unexpectedly, this model turns out to be efficient for the description of generic multi-ribbon structures in the anemone flares as well. Results. As follows from our numerical simulation, displacement of a single magnetic source (sunspot) with respect to three other sources results in a complex transformation from three to four ribbons and then again to three ribbons, but with an absolutely different arrangement. Such structures closely resemble the observed patterns of emission in the anemone microflares.

A theoretical model for the formation of Ring Moat Dome Structures: Products of second boiling in lunar basaltic lava flows

Newly documented Ring Moat Dome Structures (RMDSs), low mounds typically several hundred meters across with a median height of ~3.5 m and surrounded by moats, occur in the lunar maria. They appear to have formed synchronously with the surrounding mare basalt deposits. It has been hypothesized that they formed on the surfaces of lava flows by the extrusion of magmatic foams generated in the flow interiors as the last stage of the eruption and flow emplacement process. We develop a theoretical model for the emplacement and cooling of mare basalts in which the molten cores of cooling flows are inflated during the late stages of eruptions by injection of additional hot lava containing dissolved volatiles. Crystallization of this lava causes second boiling (an increase in vapor pressure to the point of supersaturation due to crystallization of the melt), generating copious quantities of vesicles (magmatic foam layers) at the top and bottom of the central core of the flow. Flow inflation of many meters is predicted to accompany the formation of the foam layers, flexing the cooled upper crustal layer, and forming fractures that permit extrusions of the magmatic foams onto the surface to form domes, with subsidence of the subjacent and surrounding surface forming the moats. By modeling the evolution of the internal flow structure we predict the properties of RMDSs and the conditions in which they are most likely to form. We outline several tests of this hypothesis.

What triggered the early-stage eruption of the Emeishan large igneous province?

AbstractThe formation of the Emeishan large igneous province is widely regarded as being related to a mantle plume, but plate tectonics may also have played an important role. We analyzed the regional facies architecture of the early-stage subaqueous volcanic rocks of the central Emeishan large igneous province. The results suggest that these rocks were emplaced in a N-S–striking subaqueous rift, which existed immediately before the onset of volcanism and was persistently maintained during the early eruption stage. By linking this conclusion with the background information indicating that (1) the basaltic geochemistry in this section is indicative of a subcontinental lithospheric mantle source rather than a mantle plume source, and (2) the western Yangtze plate, where the Emeishan large igneous province was developed, was located in the back-arc region of the Permian Paleo-Tethys subduction system, we propose a new view that the early-stage eruptions of the Emeishan large igneous province were triggered by back-arc extension. The dominant functioning of the mantle plume occurred shortly after this process and inherited it, as evidenced by the following: (1) The subaqueous volcanic architecture showing back-arc geochemical affinity is laterally restricted in the presumed rift, but the overlying subaerial lavas showing plume-related geochemical features overwhelmingly flooded the whole province; (2) vertically, the source of the basaltic component in these intrarift sequences underwent a gradual transition from lithospheric origin to mantle plume origin along the stratigraphic order, as evidenced by an intercalated basaltic succession showing mixed geochemical features from the two contextual origins.