Time Of Eruption Research Articles

Natural processes leading to large, pre-historic hydrothermal eruptions in geothermal areas: Rotokawa geothermal field, New Zealand

Hydrothermal eruptions are the most violent and hazardous phenomena within geothermal fields. The largest of these may produce kilometer-sized craters and breccia deposits that are tens of meters thick. The geological and hydrothermal priming that leads to these types of eruptions is poorly understood. To understand large hydrothermal eruptions, we investigated a series of prehistoric events at the Rotokawa geothermal field in New Zealand. By revising the stratigraphy and distribution of hydrothermal breccia deposits and correlating these with componentry, crater morphology, and subsurface geological structure, we estimated the frequency, priming processes, triggers, and dynamics of multiple eruptions. Seventeen large hydrothermal eruptions occurred centuries to millennia apart in the period from ca. 22 cal ka B.P. to ca. 3.4 cal ka B.P. Of six hydrothermal eruptions since ca. 7 ka, four produced oval-shaped craters up to 2 km in diameter, creating a broad, shallow depression within the geothermal field. The two youngest eruptions occurred northeast of earlier eruption centers and have narrower and elongated vents. We infer that in the central depression, newly formed craters rimmed by breccia deposits and high-relief country rock hosted temporary lakes tens of meters deep. Crater-lake breakout(s) and/or seismic events caused sudden pressure reduction above the hydrothermal aquifer, triggering hydrothermal eruptions. Northeast of the basin, hydrothermal alteration produced caprocks above intensively fractured areas. In this case, earthquakes are the most likely trigger for cap-rupture and eruption. All eruptions excavated shallow and large craters mostly within partially altered Oruanui Formation and pre-fragmented breccias. The size and localization of the eruptions was likely due to a combination of (1) availability of undisturbed porous ignimbrite hosting large thermal aquifers, (2) efficient crater excavation within or alongside pre-fragmented breccia, and (3) the location of fracture and fault zones that channeled deep fluid upflow, favoring priming processes. This study highlights how an interplay of tectonic, magmatic, and hydrologic processes is responsible for the timing, dynamics, and ultimate size of hydrothermal eruptions in geothermal fields. Some events may be very large and destructive depending on the right priming and geological conditions.

Oral and Dental Health Knowledge and Attitudes among Parents of Children

Objective: This study aims to evaluate parents’ knowledge and attitudes level on oral and dental health.
 Methods: One hundred and thirty parents of children aged 6-12 years, were invited to participate in the study. A 33-item questionnaire covering socio-demographic characteristics, dental attitude, dietary practices, tooth eruption, dental caries, and oral hygiene practices, was distributed to parents. The relationship between categorical variables was tested with the Chi-square test.
 Results: The sample comprised of 100 parents with a mean age of 37.1 ± 6.4. The knowledge and attitudes towards dental caries and oral health habits among parents did not differ significantly according to the parents’ gender, education level, or dental chair experience. There was a statistically significant difference in the responses of the first primary tooth and the first exfoliating primary tooth according to the gender of the parents (p=0.031, p=0.002, respectively). Although the education level of the parents did not affect the answers about the number of primary and permanent teeth, a statistically significant difference was found in the time of first primary tooth eruption (p=0.008).
 Conclusion: The study showed that parents do not have enough knowledge and awareness of dental caries and oral healthcare. Oral healthcare should be promoted as a part of general health and the awareness of the public should be increased.

Integrating global geochemical volcano rock composition with eruption history datasets

The major element composition of volcanic rocks carries important information about the source and differentiation processes affecting the magma, the physical properties that allow it to erupt, and its eruptive style. Although global rock geochemical databases exist, these are not linked to volcanic eruption history which hampers our global understanding of the relationship between magma composition and eruption dynamics. Here, we integrate two global databases, the Geochemistry of Rocks of the Oceans and Continents (GEOROC) and the Holocene volcanoes of the world of the Global Volcanism Program (VOTW-GVP). The integration is based on matching the location name, geographic position and eruption time, which is automated by a tool called DashVolcano. The tool is open-source, accessible at https://github.com/feog/DashVolcano, and gives access to the integrated datasets via an interactive dashboard. DashVolcano is based on more than 138,000 volcanic rock samples and provides the basis for the identification of global relationships between eruption styles, volcano types, and rock composition for more than 700 volcanoes and their eruptions for the last 10,000 years. The combined record of the eruptive history and its corresponding geochemical rock composition that DashVolcano provides can be used for characterizing global geochemical differences between volcanoes, and should also prove useful for improved long-term hazard and risk evaluations.

Therapeutic efficacy and safety of the use of the homeopathic preparation during teething in children

Introduction. The variability of the dentition terms is caused by numerous factors: the age and health of the parents, the parity, etc. Children may experience discomfort, which may be relieved by various pharmacological and non-pharmacological methods. Aim. To study the effect of factors on the temporary teeth eruption in children, the severity of discomfort symptoms and the therapeutic efficacy of a homeopathic medicine during the period of dentition.Materials and methods. The study included patients aged 4 months to 2 years. All children were divided into two groups. Group I included 97 apparently healthy children, Group II included 318 children with verified somatic pathology, who had residual effects of the perinatal hypoxic nervous system injury.Results and discussion. The analyses of correlation relationship between the dentition terms and medical and biological factors during pregnancy and childbirth in children showed the pronounced relationships: in group I – between the 53rd tooth eruption timing and the age of the mother, the mother’s disease during pregnancy, the threat of miscarriage (r = 0.98, p < 0.05); in group II – a high correlation coefficient between the 65th tooth eruption timing and acute infections suffered by the mother during pregnancy (r = 0.76; p < 0.05). Symptoms associated with teething were observed in 61% of children in group I and 72% (p < 0.05) in group II. Given the low awareness of parents about the homeopathic medicine (8.5%), we gave a talk and suggested using a homeopathic medicine during the next tooth eruption in a child.Conclusions. The temporary teeth eruption timetable is influenced by the course of the antenatal period, the mother’s age and the residual effects of the perinatal hypoxic nervous system injury. The homeopathic medicine is indicated to relieve symptoms of discomfort during the dentition period in the first year of life.

Differences in volcanic risk perception among Goma's population before the Nyiragongo eruption of May 2021, Virunga volcanic province (DR Congo)

Abstract. Risk perception is an essential element to consider for effective risk management at the time of eruption, especially in densely populated cities close to volcanoes like Goma in the east of the Democratic Republic of the Congo, which is highly exposed to volcanic hazards from Nyiragongo. The perception of volcanic risk involves the processes of collecting, selecting and interpreting signals about uncertain impacts of volcanic hazards. Using a questionnaire survey, this study describes the spatial differences and factors influencing the individual volcanic risk perception of 2224 adults from eight representative neighbourhoods of Goma before the May 2021 Nyiragongo eruption. A composite risk perception indicator was built from the perceived severity and perceived vulnerability. Statistical analysis of the survey's results shows that the risk perception was high (mean = 3.7 on a five-point Likert scale) and varies less with demographic and contextual factors than with cognitive and psychological factors. Volcanic hazards were perceived to be more threatening the city and its functioning than the individuals themselves. The spatial analysis shows that respondents from the eastern neighbourhoods, affected by the 2002 eruption, demonstrated a significantly higher level of risk perception than participants living in the western neighbourhoods. This study will help to improve volcanic risk awareness raising in Goma.

Spatial and Temporal Quantification of Subaerial Volcanism From 1980 to 2019: Solid Products, Masses, and Average Eruptive Rates

AbstractVolcanism is one of the main mechanisms transferring mass and energy between the interior of the Earth and the Earth's surface. However, the global mass flux of lava, volcanic ash and explosive pyroclastic deposits is not well constrained. Here we review published estimates of the mass of the erupted products from 1980 to 2019 by a global compilation. We identified 1,064 magmatic eruptions that occurred between 1980 and 2019 from the Smithsonian Global Volcanism Program database. For each eruption, we reported both the total erupted mass and its partitioning into the different volcanic products. Using this data set, we quantified the temporal and spatial evolution of subaerial volcanism and its products from 1980 to 2019 at a global and regional scale. The mass of magma erupted in each analyzed decade ranged from 1.1–4.9 × 1013 kg. Lava is the main subaerial erupted product representing ∼57% of the total erupted mass of magma. The products related to the biggest eruptions (Magnitude ≥6), with long recurrence times, can temporarily make explosive products more abundant than lava (e.g., decade 1990–1999). Twenty‐three volcanoes produced ∼72% of the total mass, while two different sets of 15 volcanoes erupted >70% of the total mass of either effusive or explosive products. At a global scale, the 10 and 40‐year average eruptive rates calculated from 1980 to 2019 have the same magnitude as the long‐term average eruptive rates (from thousand to millions of years), because in both cases rates are scaled for times comparable to the recurrence time of the biggest eruptions occurred.

The Effect of Vitamin Use During Pregnancy on First Tooth Eruption Time in Postpartum Period

Objective: Vitamin supplements are commonly used to support the nutritional status of pregnant women during gestation. In this multidisciplinary study, we discussed the relationship between the three most used vitamin supplements in the Turkish population (vitamin D, vitamin B complexes, and multivitamins prepared for pregnant women) during pregnancy and tooth eruption time in babies. Methods: The data of approximately 1,000 patients who gave birth in the obstetrics and gynecology clinic of our university were retrospectively reviewed. The babies of 145 patients who could be reached and who met the inclusion criteria were followed up in their postnatal period. Babies' first tooth eruption time, presence of caries, use of breast milk, and number of missing or excess teeth according to the month were determined. Results: No statistically significant differences were found between the groups regarding maternal age, infant age, number of caries, breast milk use, or the number of missing/excessive teeth. However, it was found that patients who took vitamin D + B and patients who took only vitamin B had significantly earlier first tooth eruption times than those who used all three vitamins. The patients who used three vitamins had the latest tooth eruption time. There was no statistically significant difference between first tooth eruption time and maternal age or breast milk use. Conclusion: The use of vitamins in pregnant women can affect babies' oral–dental systems, which develop while they are still in their mother's womb. More detailed information on the use of vitamins is needed in the future

Apexogenesis and Apexification - Review

The role of dental pulp in the development of the teeth. Young patients with infected or damaged tooth pulp still present a challenge among practitioners due to the degree of tooth development, more specifically the permanent teeth that have not completed their root development. At the time of eruption, only two thirds of the tooth root is developed. If there is a disruption of pulp vitality before the full root development, the root growth and dentin formation stop, resulting in reverse-tapered or flared roots and an opened apex, which will make the future root canal treatment difficult. In these cases, we can find teeth with short roots, very thin walls and an inadequate crown-root ratio. The thing root walls increase the risk of fracture. We currently have several therapies available to treat these teeth, which we will discuss further on.

CONDITION OF HARD TISSUES OF TEETH IN CHILDREN WITH CEREBRAL PALSY

The data we obtained on the prevalence of dental caries in children with cerebral palsy indicate a mass incidence, according to the WHO, 95.83 ± 3.29% (in the control group – 41.67 ± 2.29%) with the intensity of the lesion 9, 96 ± 0.21 conventional units for dental caries and 10.32 ± 0.48 conventional units for carious cavities. Analyzing the structure of the DMF index, it should be noted that dental caries is 5.57 ± 0.22, filled teeth – 2.34 ± 0.28, extracted teeth – 1.89 ± 0.1. Acute initial caries of permanent teeth was found in 45.83% of cases with an average intensity of 4.05 ± 0.21 conditional units. The evaluation of the oral hygiene index according to the OHI-S index showed its low index and, accordingly, the "good" state of oral hygiene in only 12.5% of cases. The average value of the OHI-S index and, accordingly, a "satisfactory" state of hygiene was recorded at 25.0%, a high index of OHI-S ("unsatisfactory" hygiene) – at 29.17% and a very high index of OHI-S ("poor" hygiene) – in 33.33% of cases. The evaluation of the timing of teeth eruption revealed a delay in their eruption in 45.83% of patients. The analysis of the condition of the hard tissues of the teeth, in particular acute initial caries, shows that motility disorders in children with cerebral palsy require corrective exercises to form the manipulative function of the hand, improve skills and abilities related to the performance of individual oral hygiene.

Stochastic Modeling of the Eruption History of Nyiragongo Volcano in the Virunga Volcanic Province, Western Branch of the East African Rift System

The modeling of statistical distribution of the eruptive frequency provides basic information to quantitatively assess the volcanic hazard and constrain the physics of the eruptive process. Here, we discuss the statistics of the time series of lateral eruptions of the Nyiragongo volcano in the Virunga Volcanic Province, western branch of the East African Rift System. We examine eruption data with a volcanic explosivity index of at least 1 listed in the Global Volcanism Network Bulletins. After investigating the completeness, stationarity, and independence of the eruption time series, we employ five distribution models (Brownian passage time, gamma, log-logistic, lognormal, and Weibull) to fit the repose time. First, we identify a clear tendency for events to cluster in time. We hypothesize two clusters, the ‘pre-1927’ cluster related to the intracraterial and volcanic activity of the lava lake, and the ‘post-1977’ cluster mainly related to lateral eruptions (i.e. those potentially generating lava flows). Using the maximum likelihood estimations, we evaluate the model parameters with a 95% confidence interval. Next, we use the Akaike Information Criterion to determine the most suitable distribution and we perform the Bayesian Model Averaging approach to assess uncertainty issues in model selection process. The results suggest that the BPT distribution provides the best fit for data of lateral eruptions (post-1977). Then we estimate the time-dependent probability of the occurrence of a lateral eruption for the 50-year period between 2022 and 2072. The estimates reach 50.79%, 88.61%, 97.59%, 99.50%, and 99.89% for 2032, 2042, 2052, 2062, and 2072 years, respectively.

Permanent Tooth Eruption Patterns in Nigerian Local Pigs.

Pigs are diphyodonts with heterodont dentition and have been used in studies involving teeth and jawbone regeneration, and dental implants. Patterns of tooth eruption are used to age animals and determine the effects of environmental and genetic influences on occurrence of variations. As with other species, variations exist in the tooth eruption pattern in pigs. The aim of this study was to determine the permanent teeth eruption patterns of Nigerian local pigs. Twenty-six healthy pigs were observed throughout the study period. Pigs were firmly held in dorsal or lateral recumbency and their mouths gently held open to visually examine all quadrants of the dental arches (right and left maxillary, right and left mandibular). Observations were recorded from 16 weeks of age, until the last permanent tooth erupted. Results obtained from the study showed that males had lower mean values for eruption time (54%) of examined teeth in comparison to females. The mean values of eruption time for the maxillary third incisor, the mandibular and maxillary canines, and the mandibular fourth premolar teeth were statistically significant in the males (P = .0017, P = .0088, P = .0002 and P = .0244, respectively). Sixty-nine percent of the adult pigs did not have eruption of the mandibular first premolar, while polydontia was observed in the maxillary and mandibular incisors. These results show that intra-breed and inter-breed variations exist in the dental eruption pattern in pigs. The data obtained from this study can be used for comparative dental studies and can aid further research on the developmental anatomy of Nigerian local pigs.

A possible sea-level fall trigger for the youngest rejuvenated volcanism in Hawaiʻi

Many intraplate oceanic islands undergo “rejuvenated” volcanism following the main edifice-building stage. Honolulu features Hawaiʻi’s most recent rejuvenated volcanism. K-Ar dating of Honolulu volcanism suggests that it started at ca. 750 ka and ended at <100 ka. Here, we present new 40Ar/39Ar ages and olivine diffusion modeling from Koko Rift lavas to resolve when the most recent Honolulu eruptions occurred and to evaluate possible mechanisms of rejuvenated volcanism and volcanic hazards. Diffusion modeling of olivine zoning profiles in Koko Rift basalts suggests that magmas were stored in the crust for many months prior to eruption. Six new 40Ar/39Ar ages cluster at 67 ± 2 ka (2σ), which demonstrates that Koko Rift is Hawaiʻi’s youngest known area of rejuvenated volcanism. The timing of Koko Rift eruptions coincides with the pronounced drop in global sea level (∼100 m) during Marine Isotope Stage 4. This major sea-level fall may have triggered the eruptions of Koko Rift magmas that were stored in the crust for months to years at < 15 km depth. The proposed mechanism is similar to that at other volcanic islands, which suggests that changes in global sea level may have significant control on the magnitude and frequency of eruptions at ocean island volcanoes.

Geochronology and geochemistry of the Panjal Traps from the southern Pir Panjal Range, Kashmir, India

The eruption of the Panjal Traps is associated with rifting along the Tethyan margin of Gondwana. A CA-ID-TIMS zircon U-Pb age of basalt collected from the southern Pir Panjal Range (SPPR) yielded a weighted-mean 206Pb/238U age of 288.2 ± 0.3 Ma. The rocks from the SPPR can be divided into three compositionally distinct groups (basalt: SiO2 < 52 wt%; Mg# = 56–36, basaltic andesite: SiO2 = 52–60 wt%; Mg# = 32–48, and silicic: SiO2 > 64.0 wt%; Mg# = 27–23) and are chemically correlated with rocks from the eastern Kashmir Valley rather than the northern Pir Panjal Range (NPPR). The Sr-Nd isotopes (87Sr/86Sri = 0.70860–0.71104; εNd(t) = −6.1 to −4.4) of the mafic rocks are similar and indicate that their magmas were derived from a subduction modified subcontinental lithospheric mantle (SCLM) source. The silicic rocks were derived by partial melting of the continental crust (87Sr/86Sri = 0.71022–0.71093; εNd(t) = −8.7 to −7.2) and their discovery in the SPPR indicates that silicic volcanism was far more extensive than previously thought. The 187Os/188Osi isotopic ratios of basalts from different regions of the Panjal Traps range from 0.1230 to 0.2832. Two samples from the NPPR have ratios of 0.1230 and 0.1256 that are slightly higher than primitive upper mantle at the time of eruption whereas the remaining samples show enriched values (0.1343–0.2832). The new data suggest that it is likely that the mantle source of the Panjal Traps transitioned from a SCLM source to a sublithospheric source over time as seafloor spreading developed.

Breastfeeding Effect on Primary Teeth Emergence in Relation to Craniofacial Growth among Iraqi Infants

Background: Breastfeeding is more than just nutrition; it can be viewed as a natural orthotic device for the harmonious development of the face. Sucking has an impact on a child’s premaxillary region’s growth, and mandibular movements encourage mandibular growth. Along with the advantages for general health, breastfeeding also helps with the right development of teeth, face muscles, and occlusion. Hence symmetric, well-proportioned face and appropriate occlusion depend on balanced facial growth. Objectives: This study aims to evaluate the effect of breastfeeding on the timing of teething in relation to craniofacial development. Materials and Methods: This study is a cross sectional comparative study concerning craniofacial growth assessment, with prospective view concerning timing of eruption. Sample was composed of 100 breastfed infants compared with 100 infants depending on formula milk. Clinical examinations and follow-up for teeth emergence was done for whole sample. Results: Breastfeeding was found to be associated with early teeth emergence. Additionally, although, there were no significant differences between facial growth and feeding pattern there was a significant correlation between delay eruption time of primary dentition and facial growth parameters (mandible and maxilla depths) among bottle-feeding group. Conclusion: The current study confirms the effect of breastfeeding on the early teething emergence of primary dentition; however, there were no significant differences between type of feeding and facial growth parameters. While a significant relation between delay eruption time and facial growth parameters (mandible and maxilla depths) was found among bottle-feeding infants.

Association between obesity and early tooth eruption in adolescents: Findings from a popu-lation-based cohort study in southern Brazil.

Obesity is a prevalent chronic condition affecting children and adults worldwide, and it seems to influence the timing of tooth eruption. The aim of this study was to assess the as-sociation between weight status at age 12 and the eruption of permanent teeth at ages 12 and 14-15 among schoolchildren from southern Brazil. A cross-sectional survey was conducted in Porto Alegre, southern Brazil, and included a representative sample of 1,528 12-year-old schoolchildren. After 2.5 years, 801 individuals were reexamined. Baseline data collection included a questionnaire, the record-ing of anthropometric measures (height and weight), and clinical examination to register the number of erupted permanent teeth. At follow-up, the eruption stage of second perma-nent molars was recorded. Statistical analysis used Poisson regression. Overweight and obese individuals were 32% and 88% more likely to have com-plete permanent dentition at age 12, respectively (overweight, PR=1.32, 95%CI=1.13-1.55; obese, PR=1.88, 95%CI=1.75-2.02). Obese 12-year-olds were more likely to present erupt-ed #17, #27, #37, and #47 at age 12 and to present completely erupted second molars at age 14-15 than normal weight ones. This population-based study found a significant association between over-weight/obesity at age 12 and early tooth eruption at ages 12 and 14-15 among schoolchil-dren from southern Brazil. Key words:Tooth eruption, Obesity, Permanent teeth, Epidemiology.

Evaluation of Tooth Brushing Habits in Preschool Children – A Cross-Sectional Survey

Background Tooth brushing behaviours in children have been significantly associated with their oral health status and susceptibility to dental caries. Adoption of proper and consistent tooth brushing habits early in life will help in establishing the same in their adulthood. Therefore this study aimed to understand and assess the tooth brushing habits of preschool children in Bengaluru city Karnataka.Methodology Primary caregivers of 102 preschool children from selected preschools in Bengaluru were included in the study. A self-administered questionnaire was distributed and the responses were collected. The questionnaire consisted of questions pertaining to demographic information of both the child and the parents and questions regarding the tooth brushing habits of children. All the responses were tabulated and subjected to statistical analysis.Results It was noted that 60 of the primary caregivers introduced tooth brushing to their children from 6 months to 1 year of age which coincided with the time of eruption of the first tooth in the oral cavity. The majority of the children 61 did not brush their teeth twice daily and this showed a significant association with the frequency of brushing of mothers with 59 of mothers reporting to brushing their teeth once a day. It was reported that 58 of the pre-schoolers brushed their teeth on their own without any adult supervision. It was alarming to see that 70 of the caregivers did not receive any information or education pertaining to the maintenance of oral hygiene in their children.Conclusion The results of this study highlight the urgent need for the establishment of proper oral hygiene habits in young children as this behaviour is amenable to change leading to a positive impact on oral health.

Social and Behavioural Risk Factors of Early Childhood Caries Among Children Aged 4–47 Months: A Cross-Sectional Study

Aim: This study aimed to investigate various risk factors for early childhood caries in a paediatric population in Edirne, Turkey. Methods: This cross-sectional study included 1197 children aged 4–47 months old who visited family health centres for routine control. Questionnaires were used to collect data on parental- and pediatric-related variables potentially associated with early childhood caries. Oral hygiene was scored using the Visual Plaque Index, and decayed teeth, missing teeth, filled surfaces and carious teeth were recorded. We evaluated risk factors for early childhood caries using a hierarchical regression analysis model. Results: Of the 1197 children, 219 (18.3%) had dental caries. The mean age of the children in the caries group was 33±7 months old, and the mean filled surfaces and carious teeth values were 4.84±3.49 and 8.50±8.30, respectively. Younger age at the time of first tooth eruption, current height percentile higher than 96, poor oral hygiene, older age, having siblings, and paternal age younger than 30 years old at the time of the child’s birth were associated with an increased risk of early childhood caries. Conclusion: Prevention policies on caries among young children should focus on the first years of a child's life. Non-dental healthcare professionals may play an important role in being the first contact with parents in the healthcare system for anticipatory guidance. Keywords: oral health, dental caries, preschool children, risk factors, preventive care

Obsidian in Ethiopia: a Geoarchaeological perspective

In Ethiopia, obsidian is mainly found in the Afar Depression and the Main Ethiopian Rift. The compositional and petrological features of these obsidians vary. Some volcanic centers show that varying volcanic eruptions from a single center may not necessarily imply variable chemistry. Obsidian has been dated using K/Ar, Ar/Ar, and fission track methods to determine the time of eruption but there are also a few dates on artifacts by hydration dating to establish the time of tool manufacture. Many of the geological sources were utilized by prehistoric populations beginning at least since the Early Stone Age but obsidian became commonly used during the Middle Stone Age. Obsidian based stone tool use for scraping in Ethiopia persisted until recent times.

The Qixiangzhan eruption, Changbaishan-Tianchi volcano, China/DPRK: new age constraints and their implications

Zircon double dating (ZDD) of comendite lava reveals an eruption age of 7.0 ± 0.9 ka for the Qixiangzhan eruption (QXZ), Changbaishan-Tianchi volcano, China/DPRK. This age is supported by new 40Ar/39Ar sanidine experiments and a previous age control from charcoal at the base of the QXZ. The revised age supports correlations with distal ash in Eastern China and Central Japan and establishes a significant (estimated at Volcanic Explosivity Index 5+) eruption that may provide a useful Holocene stratigraphic marker in East Asia. The new age indicates that the QXZ lava does not record a ca. 17 ka Hilina Pali/Tianchi geomagnetic field excursion but rather a heretofore unrecognized younger Holocene excursion at ca. 7–8 ka. Comparison between U–Th zircon crystallization and ZDD as well as 40Ar/39Ar sanidine ages indicates a protracted period of accumulation of the QXZ magma that extends from ca. 18 ka to the eruption age. This connotes an eruption that mixed remobilized early formed crystals (antecrysts) from prior stages of magma accumulation with crystals formed near the time of eruption. Based on these results, a recurrence rate of ca. 7–8 ka for the Changbaishan-Tianchi magma system is found over the last two major eruption cycles.

A theoretical model for simulating periodic processes of intermittent karst springs considering changed recharge rates into siphon cavity

Intermittent karst springs (IKS) are common phenomena in karst areas where spring flow rates rise and fall in variable periods, which is generally attributed to the siphon structure in karst aquifers. However, the previous model assumed that the siphon cavity received a fixed recharge rate, thus the IKS showed a fixed periodic characteristic. In this study, an improved theoretical model (IKS model) was proposed to simulate the hydrological process of IKS with changing periods by considering the varying recharge rate from aquifers to the siphon cavity. The model uses two tandem tanks to represent the karst aquifer and siphon cavity separately. The numerical solution was obtained by the iterative method to predict the periodic variations of flow rate and eruption time of IKS. The IKS model was verified by physical experiments under four representative recharge conditions, showing good consistency between theoretical and experimental results. It reveals the hydrologic processes mechanism of the IKS by quantitatively describing the relationship between the cycle period of the IKS discharge variations and the flow exchanges in the siphon cavity-aquifer system. Furthermore, this model performs well in simulating the hydrological process of Chaoshuidong Spring in central China and approximately estimated the hydraulic coefficient of the aquifer in the basin based on observed periodic changes in spring discharge. These findings might be essential for the development, management, and protection of groundwater resources in IKS.