Eruption Of Mount Research Articles

Microbial community structure in recovering forests of Mount St. Helens

IntroductionThe 1980 eruption of Mount St. Helens had devastating effects above and belowground in forested montane ecosystems, including the burial and destruction of soil microbes. Soil microbial propagules and legacies in recovering ecosystems are important for determining post-disturbance successional trajectories. Soil microorganisms regulate nutrient cycling, interact with many other organisms, and therefore may support successional pathways and complementary ecosystem functions, even in harsh conditions. Historic forest management methods, such as old-growth and clearcut regimes, and locations of small mammal enclo and clearcut forests, as well as in locations of historic short-term gopher enclosures (Thomomys talpoides), to evaluate community response to forest management practices and to examine vectors for dispersing microbial consortia to the surface of the volcanic landscape. These biotic interactions may have primed ecological succession in the volcanic landscape, specifically Bear Meadow and the Pumice Plain, by creating microsite conditions conducive to primary succession and plant establishment.Methods and resultsUsing molecular techniques, we examined bacterial, fungal, and AMF communities to determine how these variables affected microbial communities and soil properties. We found that bacterial/archaeal 16S, fungal ITS2, and AMF SSU community composition varied among forestry practices and across sites with long-term lupine plots and gopher enclosures. The findings also related to detected differences in C and N concentrations and ratios in soil from our study sites. Fungal communities from previously clearcut locations were less diverse than in gopher plots within the Pumice Plain. Yet, clearcut meadows harbored fewer ancestral AM fungal taxa than were found within the old-growth forest.DiscussionBy investigating both forestry practices and mammals in microbial dispersal, we evaluated how these interactions may have promoted revegetation and ecological succession within the Pumice Plains of Mount St. Helens. In addition to providing evidence about how dispersal vectors and forest structure influence post-eruption soil microbiomes, this project also informs research and management communities about belowground processes and microbial functional traits in facilitating succession and ecosystem function.

Melt embayments record multi-stage magma decompression histories

Over the last decade, the melt embayment has proven its merit as a robust petrological tool capable of recording magma decompression rates for explosive eruptions. However, the models developed and applied to extract this information from embayments have not accounted for the complexity and nonlinearity of magma flow in the conduit. We present Embayment Decompression in Two Stages (EDiTS): a numerical model for extracting magma decompression rates from measured volatile diffusion profiles preserved in crystal-hosted embayments, approximating magma acceleration using two constant-rate decompression paths. This model solves for three unknown parameters: initial (deeper) and final (shallower) decompression rates, as well as the pressure where a transition occurs. We successfully benchmark EDiTS against existing numerical diffusion models, and use controlled multi-stage decompression experiments on natural quartz-hosted embayments to test the ability of our model to recover known decompression paths. We find that EDiTS is able to closely approximate the known two-stage path in the mixed-volatile (H2O + CO2) experiment, while a constant-rate modeling approach is unable to simultaneously fit H2O and CO2 gradients. However, in the H2O-saturated experiment, there is no unique solution to the resulting gradient, with both constant-rate and two-stage models reproducing the measured profile, and EDiTS notably overestimating the known total ascent time by several hours. Using decompression experiments, we show that constant-rate models can provide misleadingly good fits to embayment H2O gradients produced by more complex decompression histories, and thus the measurement and modeling of multiple diffusing species, when available, can provide crucial constraints. We then apply EDiTS to re-evaluate mixed-volatile embayment datasets from explosive silicic arc and caldera-forming eruptions from five volcanic centers (Yellowstone, WY, USA; Bandelier, NM, USA; Long Valley, CA, USA; Taupo, NZ; Mount St. Helens, WA, USA), where all systems contain initial CO2. In contrast to the minutes to hours of total ascent time extracted from embayment volatile profiles using constant-rate models, our two-stage model resolves slower initial ascent times that span several to >10 h. Final ascent rates are 1–2 orders of magnitude faster than the initial extracted rates, in agreement with theoretical conduit flow model predictions. Application of EDiTS to embayments from the May 18th, 1980 eruption of Mount St. Helens results in an initial stage of ascent on the order of hours consistent with the timing of magma arrival at the surface from the seismically-inferred storage region (7–9 km) ~3.5 h after the initial blast, and a final stage of ascent (<1–5 min) in close agreement with time-integrated bubble number densities. Our combined numerical, experimental, and natural results suggest that, with the application of more advanced models, the melt embayment can provide a complete picture of magma decompression timescales from the deep conduit to the surface.

Determination of Mount Eruption Insurance Premiums in Indonesia Based on Collective Risk and Level of Risk Spread

Volcano eruption insurance is an insurance product that provides financial protection to policy holders who experience losses due to volcanic eruptions. This insurance product is still rarely developed in Indonesia, even though this country is very vulnerable to natural disasters. Therefore, this research aims to carry out a simulation of determining volcanic eruption disaster insurance premiums based on collective risk and the level of risk distribution. The data used in this research is the frequency of events and economic losses due to volcanic eruptions. Event frequency and loss data are analyzed using a collective risk model. Apart from that, determining insurance premiums also takes into account loading factors and the level of risk distribution from volcanic eruption disaster data. From the results of the analysis, it was found that natural disaster insurance premiums had increased, along with an increase in the loading factor provided. In addition, insurance premium expenses are influenced by the collective risks faced by customers. The greater the collective risk faced, the greater the insurance premium that customers must bear. Based on the results of the estimates carried out, it is hoped that this research can provide an overview to the Indonesian government in estimating the Mount Meletus insurance scheme. Meanwhile, insurance companies can get an idea of determining insurance premiums according to conditions in the field.

Lived Experience of Survivors during Semeru’s Mount Eruption in East Java, Indonesia

Background: To date, there is no studies have examined the response to loss and grief in disasters because the impact of disasters is seen in the form of psychopathology. Researching grief can provide pivotal information for developing tailored instruments and interventions especially in nursing. Purpose: This study will explore various loss and grief experiences and coping strategies experienced by survivors of the eruption of Mount Semeru in East Java, Indonesia. Methods: This study uses a qualitative approach with phenomenological methods. There were six informants in this study drawn from various professions and survivors who fled both in refugee camps and in residents' homes. Results: There are three categories of grief responses: denial, anger, and acceptance. Coping strategies focus on emotions and problem-solving. The grieving response experienced by respondents does not have to go through the phases of denial, anger, bargaining, depression, and acceptance. Conclusion: These show that differences in grieving responses are influenced by the background of the events experienced, previous grieving experiences, gender, culture, and others. Most of the communities affected by the eruption of Mount Semeru have low coping mechanisms.

Spatial distribution and analysis of safe schools in Selo District, Boyolali Regency, Indonesia

Selo District is one of the districts in Boyolali Regency, which is closest to the peak of Mount Merapi. The study aimed to determine (1) the spatial distribution of elementary schools in Selo district, (2) analyze the level of school’s vulnerability to the Mount Merapi eruption, and (3) the readiness of the safe school to deal with the Merapi mount eruption. This research is a qualitative descriptive study with a spatial approach. They are determining the location and condition of each school by direct observation in the field using GPS; data on school readiness in dealing with volcanic eruption disasters with in-depth interviews with school principals. The results showed that (1) There were 27 elementary schools, two junior high schools, and one high school in Selo District, which were evenly distributed; (2) There are five schools of which are included in Disaster Prone Areas (KRB) 2, there are SDN-1 Telaga Lele, SDN-2 Telaga Lele 1, SDN-3 Jrakah, SDN-2 Klakah, and SDN-1 Suroteleng. (3) Most of the school’s preparedness for the eruption of Mount Marapi is low, although there are already teachers representing schools who have undergone disaster training.

Canopy development influences early successional stream ecosystem function but not biotic assemblages

Determining how streams develop naturally, particularly the ecological role of newly developed riparian canopy cover, is essential to understanding the factors that structure new stream communities and provides valuable information for restoring highly disturbed ecosystems. However, attempts to understand primary succession in riverine ecosystems have been hindered by a lack of data owing to the infrequent formation of new rivers on the landscape. In the present study, we used five streams formed following the 1980 eruption of Mount St. Helens (WA, USA) to examine the influence of canopy cover development on algal and benthic macroinvertebrate assemblages, biomass, and organic matter processing. Newly established closed canopy reaches had less available light, but no significant differences in algal biomass or macroinvertebrate assemblages compared to open canopy reaches. Instead, algal and macroinvertebrate communities were structured mainly by hydrologic differences among watersheds. In contrast, organic matter processing rates were sensitive to canopy cover development, and rates were faster under closed canopies, especially in late summer or after terrestrial preconditioning. After 40 years of stream and riparian primary successional development, canopy cover strongly influences ecosystem function, but aquatic organism assembly was more influenced by physio-chemical and hydrologic variation. Our findings provide insight into the development of in-stream assemblages and ecosystem functions, which is also relevant to efforts to address major disturbances to stream channels, such as volcanic eruptions, floods, forest fires, and clear-cut logging.

Spatial Habitat Structure Assembles Willow-Dependent Communities across the Primary Successional Watersheds of Mount St. Helens, USA

The eruption of Mount St. Helens in 1980 resulted in a cataclysmic restructuring of its surrounding landscapes. The Pumice Plain is one of these landscapes, where tree species such as Sitka willow (Salix sitchensis) and their dependent communities have been established along newly-formed streams. Thus, the study of these dependent communities provides a unique and rare opportunity to investigate factors influencing metacommunity assembly during true primary succession. We analyzed the influence of landscape connectivity on metacommunity assembly through a novel application of circuit theory, alongside the effects of other factors such as stream locations, willow leaf chemistry, and leaf area. We found that landscape connectivity structures community composition on willows across the Pumice Plain, where the least connected willows favored active flyers such as the western tent caterpillar (Malacosoma fragilis) or the Pacific willow leaf beetle (Pyrrhalta decora carbo). We also found that multiple levels of spatial habitat structure linked via landscape connectivity can predict the presence of organisms lacking high rates of dispersal, such as the invasive stem-boring poplar weevil (Cryptorhynchus lapathi). This is critical for management as we show that the maintenance of a heterogeneous mixture of landscape connectivity and resource locations can facilitate metacommunity dynamics to promote ecosystem function and mitigate the influences of invasive species.

Gambaran Kesiapsiagaan Mayarakat Menghadapi Bencana Gunung Meletus di Dukuh Gebyog Samiran Selo Boyolali

Throughout 2018, Indonesia experienced 10 volcanic eruptions. The volcanic eruption became one of the domicile disasters in 2018. In 2019 there were 7 volcanic eruptions in the last 1 year. Volcanic eruptions that threaten and disrupt people's lives and livelihoods are caused by natural or non-natural factors that result in casualties, environmental damage, loss of property, and psychological impacts. Boyolali Regency is one of the districts that are prone to volcanic eruptions in Central Java Province. The number of relative disasters continues to increase from year to year in Boyolali City which has a location prone to volcanic disasters, especially in Selo Village. The purpose of this study was to describe the preparedness of the community to face the Mount Meletus disaster in Gebyog Samiran Village, Selo Boyolali. The type of research used is a descriptive research and the method used is a descriptive survey. The sampling technique in this study uses simple random sampling with a sample of 53 respondents. The results showed that based on the characteristics of the respondents, the majority were in the age range of 41-60 years (39.6%), female sex was (62.3%), education level was in elementary school (54.7%), and worked as a farmer (50.9%). Meanwhile, the majority of residents were in the ready category (37.7%). The description of community preparedness to face the Mount Eruption disaster in Gebyog Hamlet, Samiran Selo Boyolali, is mostly in the ready category (52.8%).

Long-term monitoring of Mount St. Helens micrometeorology.

The 1980 volcanic eruption of Mount St. Helens had profound impacts on the geology, hydrology, and ecology of its surrounding landscapes. Consequently, the event provided a unique opportunity to study ecological change over time in relation to abiotic factors. To better assess the role localized environmental conditions play in these larger processes, we have monitored micrometeorological conditions across six disturbance zones on Mount St. Helens created by the eruption. We deployed 823 environmental sensors at 191 sites from 1997 to 2022 to measure the temperature and relative humidity of aquatic (temperature only) and terrestrial habitats in these areas, collecting over 4.2 million measurements in total. Measurements were typically recorded every 30 min from late spring through mid-fall, with the exception being Spirit Lake, where temperatures have been measured hourly on a year-round basis since 2002. These data have been used to address two broad research questions: (1) how small-scale environmental conditions influence patterns of survivorship and/or establishment on Mount St. Helens post-eruption for a range of organisms, including plants, small mammals, birds, amphibians, arthropods, fish, and other aquatic biota, and (2) to quantify and compare these environmental conditions across different disturbance zones, which vary in disturbance type, intensity, and history of post-eruption secondary disturbances. Due to the repeatability of these measurements over many years, these data lend themselves to exploring the relationship between forest succession and microclimate, especially with respect to forest-dwelling organisms whose spread and demography are sensitive to temperature and relative humidity. In addition, this dataset could be used to investigate additional questions related to early succession, disturbance ecology, climate change, or volcano ecology. This dataset is available in the R data package MSHMicroMetR, which also includes an R Shiny data visualization and exploration tool. There is no copyright on the data; please cite this data paper Ecology when using these data.

Understanding and modeling tephra transport: lessons learned from the 18 May 1980 eruption of Mount St. Helens

Understanding and modeling tephra transport: lessons learned from the 18 May 1980 eruption of Mount St. Helens

Spatial distribution and temporal change of vegetation restoration after the eruption of Mount St. Helens: from 1984 to 2019

Approximately ten terrestrial volcanic eruptions occur yearly, significantly impacting the surrounding area. Mount St. Helens has been one of the most popular active volcanoes in recent years. This study analysed the vegetation cover status from 1984 to 2019. Remote Sensing and GIS technology were mainly used in this study to perform detailed research on the rates and trends of vegetation change. The results show that the vegetation in the study area has continued to recover in general, but some areas are consistently devoid of vegetation growth. After analysing the spatial and temporal perspectives, the vegetation recovery rate was relatively slow in the eastern part of the study area. This vegetation recovery status may be related to factors such as volcanic eruption, deep slope, lack of seeds, and massive wildfires. The area in the north-western part of the eruption area gained rapid growth in the first ten years, which may be caused by plant measures.

IMPLEMENTATION OF THE SUKATENDEL VILLAGE REGULATION POLICY NO. 01 OF 2019 CONCERNING THE DISASTER RESILIENT VILLAGE PROGRAM

Indonesia is an archipelagic country that is vulnerable to natural and non-natural disasters. The trend of natural disasters that occur in Indonesia itself tends to increase from year to year as well as what happened in Karo Regency. According to BPS data from 2015-2020 there was an increase in natural disasters, especially those caused by the eruption of Mount Sinabung.The problem that occurs is that Sukatendel Village is located in Tiganderket District, Karo Regency which has an altitude of 500 meters above sea level. This certainly increases the risk of disaster. The purpose of this study was to determine the effectiveness of implementing the Sukatendel Village Regulation No. 01 of 2019 regarding the Disaster Resilient Village program. With qualitative research methods. The results showed thatImplementation of Village Regulation No. 1 of 2018 concerning the disaster-resilient village program which includes 4 (four) factors, namely: The communication factor has not been carried out properly, due to the irregularity of socialization activities and the limitations of information communication tools to the surrounding community. The human resource factor is adequate in the implementation of DESTANA with the establishment of a village management and DRR Forum, but has limited budget and facilities in disaster management. The disposition factor or commitment owned by the implementor is good in carrying out its responsibilities as the implementer of the policy. The bureaucratic structure factor in the implementation of DESTANA has been directed and clear with the creation of a disaster management mechanism, the division and role of each team, but this is of course with the approval of the Karo Regency Government.

Renewed incision and complex response of the North Fork Toutle River following the eruption of Mount St. Helens in 1980

The upper North Fork Toutle River (NFTR) has been evolving in a complex way since being disrupted by a 2.5-km3 debris avalanche deposit during the catastrophic eruption of Mount St. Helens in Washington State, USA in 1980. In this study, we improved the alluvial phase space diagram (APSD), which classifies channel adjustment into different stages based on bed elevation and cross-sectional area changes, and applied it to the NFTR at annual time scale in the 1980s. The results showed that in the early 1980s, the upstream narrow single-threaded reaches were degraded, while the downstream wide anabranching reaches were aggraded, with the middle transitional reach acting as the hinge zone. Gradually, the upstream channel reaches armoured, widened, bed slope and excess stream power decreased in the late 1980s, and quasi-equilibrium occurred locally and during short time periods. Sediment load decreased at the lower reaches, resulting in bed degradation and a transition from sediment sink to source. This reversal seemed to have triggered renewed incision, which migrated upstream. The renewed incision was characterised by Stage 1/2 (bed incision with limited bank erosion) followed by Stage 2 (degradation and widening) in the improved APSD. The degradation rate accelerated in the 1990s, especially due to the big flood in 1996, and then slowed down after ∼2000. Channel adjustment rates of the renewed incision were much smaller compared to those of the initial rapid degradation. The change rates of cross-sectional area and valley width decreased by ∼58% and ∼85%, respectively. The comparison between this study and existing studies highlights the significant role played by the time scale, at which the APSD is applied to study channel morphology adjustment.

Energetic output of the 2022 Hunga Tonga–Hunga Ha‘apai volcanic eruption from pressure measurements

The violent eruption of the volcano at Hunga Tonga–Hunga Ha‘apai island on January 15, 2022, generated an intense pressure wave registered by instruments all over the world. Using public reports posted on social media, we have used the arrival time of the first passage of the wave to measure its velocity, found to be a constant 1114pm 2 km/h (309pm 1 m/s). An empirical pressure–distance relation that utilizes measurements from a large range of sources is used to estimate an energetic output. We find that this Hunga Tonga–Hunga Ha‘apai volcanic eruption released approximately the equivalent of 61 Mt, which is considerably larger than the 1980 eruption of Mount St. Helens and slightly higher than the yield of Tsar Bomba, the largest human-made explosion in history.

Volcano, Earthquake, and Tsunami Hazards of the Cascadia Subduction Zone

Subduction zones produce some of Earth’s most devastating geological events. Recent eruptions of Mount St. Helens and great earthquakes and tsunamis in Japan and Sumatra provide stark examples of the destructive power of subduction-related hazards. In the Cascadia subduction zone, large earthquakes, tsunamis, and volcanic eruptions have occurred in the past and geologic records imply that these events will occur in the future. As the population and infrastructure increase in the region, resilience to these natural hazards requires a detailed scientific understanding of the geologic forces and processes involved, combined with a society motivated to mitigate risks.

Revisiting the depth distribution of seismicity before and after the 2004–2008 eruption of Mount St. Helens

Hypocenter estimation at active volcanoes improves our understanding of their magmatic systems and indicates changing conditions at depth for continuously monitored volcanoes. The most active volcano in the Cascades Range, Mount St. Helens, has a multi-decadal earthquake catalog and it shows an apparent change in the depth distribution of seismicity before and after the 2004–2008 dome-building eruption and unrest sequence. We use two new resources to evaluate the accuracy of hypocenters and consequently the change in depth distribution of seismicity before and after the 2004–2008 eruption. First, we deployed a dense array of 136 three-component nodal seismographs for one month in 2017, including sub-arrays on the newly extruded dome and crater floor. Second, for events recorded during this month, we located their hypocenters using a three-dimensional (3D) wavefront-tracking location solver and a recently developed tomography model derived from active and passive source data. The relocated hypocenters are generally shallower and more concentrated beneath the crater compared to their catalog locations. The mean hypocenter movement from catalog locations is 2.86 km, with an averaged depth shift of 2.53 km upward. Comparison between 2017 hypocenters located using all of the available phase picks and those located using only the catalog picks from the permanent network suggests the improved hypocenters mostly resulted from the location solver and the 3D velocity model, with smaller changes due to the dense three-component array. Applying the same hypocenter estimation method to phase picks for all events from 1997 to 2004 and 2008–2021, we found a concentration of seismicity between sea level and ~ 1 km above it before and after the 2004–2008 eruption. The new results suggest that the seismogenic structure in the shallow magmatic system quickly re-equilibrated to its earlier state after the dome-building eruption.

Climatic, weather, and socio-economic conditions corresponding to the mid-17th-century eruption cluster

Abstract. The mid-17th century is characterized by a cluster of explosive volcanic eruptions in the 1630s and 1640s, climatic conditions culminating in the Maunder Minimum, and political instability and famine in regions of western and northern Europe as well as China and Japan. This contribution investigates the sources of the eruptions of the 1630s and 1640s and their possible impact on contemporary climate using ice core, tree-ring, and historical evidence but will also look into the socio-political context in which they occurred and the human responses they may have triggered. Three distinct sulfur peaks are found in the Greenland ice core record in 1637, 1641–1642, and 1646. In Antarctica, only one unambiguous sulfate spike is recorded, peaking in 1642. The resulting bipolar sulfur peak in 1641–1642 can likely be ascribed to the eruption of Mount Parker (6∘ N, Philippines) on 26 December 1640, but sulfate emitted from Komaga-take (42∘ N, Japan) volcano on 31 July 1641 has potentially also contributed to the sulfate concentrations observed in Greenland at this time. The smaller peaks in 1637 and 1646 can be potentially attributed to the eruptions of Hekla (63∘ N, Iceland) and Shiveluch (56∘ N, Russia), respectively. To date, however, none of the candidate volcanoes for the mid-17th century sulfate peaks have been confirmed with tephra preserved in ice cores. Tree-ring and written sources point to cold conditions in the late 1630s and early 1640s in various parts of Europe and to poor harvests. Yet the early 17th century was also characterized by widespread warfare across Europe – and in particular the Thirty Years' War (1618–1648) – rendering any attribution of socio-economic crisis to volcanism challenging. In China and Japan, historical sources point to extreme droughts and famines starting in 1638 (China) and 1640 (Japan), thereby preceding the eruptions of Komaga-take (31 July 1640) and Mount Parker (4 January 1641). The case of the eruption cluster between 1637 and 1646 and the climatic and societal conditions recorded in its aftermath thus offer a textbook example of difficulties in (i) unambiguously distinguishing volcanically induced cooling, wetting, or drying from natural climate variability and (ii) attributing political instability, harvest failure, and famines solely to volcanic climatic impacts. This example shows that while the impacts of past volcanism must always be studied within the contemporary socio-economic contexts, it is also time to move past reductive framings and sometimes reactionary oppositional stances in which climate (and environment more broadly) either is or is not deemed an important contributor to major historical events.

MOUNTAIN GOAT (OREAMNOS AMERICANUS) POPULATION RECOVERY AT POST-ERUPTION MOUNT ST. HELENS (LAWETLAT'ɬ A), WASHINGTON

The powerful volcanic eruption of Mount St. Helens in 1980 is commonly reported to have killed large numbers of wildlife species, including near-extirpation of the local Mountain Goat (Oreamnos americanus) population. In the decade after 2000 we increasingly received reports of goat sightings around Mount St. Helens, including nannies with kids in 2007. By 2011, we estimated 15 to 25 goats were present on the landscape. In 2014, we initiated 2 lines of research. The first was a review of historic records to document pre-eruption goat populations. The second was the establishment of an annual minimum population-size survey using simple ground-count methods. In 2015, we revised our methods, and our results between 2015 and 2020 show a general growth trend of minimum population size from 152 goats in 2015 to 200 in 2020, with a peak of 240 goats observed in 2019. In 2017 and 2020, we paired ground counts with aerial surveys (with sighting correction) to better estimate population size, and observed 246 goats (245.9, 90% CI = 232.3–260.4) in 2017 and 252 (251.7, 90% CI = 233.2–270.1) in 2020. Our 2020 aerial estimate of ∼252 goats is a population 5 times (and possibly 10 times) the size of the 20–50 Mountain Goats we speculate were present in the same landscape prior to the 1980 eruption landscape, and reveals a substantial local recovery of the species.

Clear and Present Dangers: The Multiple Health Hazards of Volcanic Eruptions.

Clear and Present Dangers: The Multiple Health Hazards of Volcanic Eruptions.

ВРЕМЕННЫЕ ИМПУЛЬСЫ КАЙНОЗОЙСКОГО ЭКСПЛОЗИВНО-ФРЕАТИЧЕСКОГО ВУЛКАНИЗМА В ЮГО-ЗАПАДНОМ ПРИМОРЬЕ. КОРРЕЛЯЦИЯ ИЗОТОПНЫХ И ФИТОСТРАТИГРАФИЧЕСКИХ ДАТИРОВОК

The Cenozoic tephra deposits - products of explosive phreatic eruptions of maar volcanoes in the southwest of Primorye are studied. The deposits represent rhyolitic ash and pumice pyroclastic beds with a high terrigenous component, including tephroid pseudo-conglomerates. Isotopic dating of tephra beds established two time pulses of explosive volcanism: 30–34 Mya and 23–24 Mya. The first time pulse coincided with the beginning of the formation of marginal seas and continental coal basins. It corresponds to the most productive stage of coal accumulation, the burial of wood wastes and their coalification at a faster rate, and the development of a high-temperature geothermal field and can be compared with the well-known catastrophic eruption of Mount St. Helens in the U.S.A. The second time pulse of explosive volcanism had a regional character of manifestation. It is characterized by the formation of green tuff complexes on submarine elevations of the Sea of Japan as well as along the western and eastern coasts of Japan. Synchronously with the volcanic activity started the acceleration of the sinking rate of the Sea of Japan bottom in response to the active rising of asthenospheric diapirs. The established isotopic ages do not conform to the ages determined for fossil leaves and pollen from the deposits, which may reflect the climate-forming type of such an explosive process.