Large-scale Volcanic Eruptions Research Articles

Source reservoir controls on the size, frequency, and composition of large-scale volcanic eruptions.

Large-scale, explosive volcanic eruptions are one of the Earth's most hazardous natural phenomena. We demonstrate that their size, frequency, and composition can be explained by processes in long-lived, high-crystallinity source reservoirs that control the episodic creation of large volumes of eruptible silicic magma and its delivery to the subvolcanic chamber where it is stored before eruption. Melt percolates upward through the reservoir and accumulates a large volume of low-crystallinity silicic magma which remains trapped until buoyancy causes magma-driven fractures to propagate into the overlying crust, allowing rapid magma transfer from the reservoir into the chamber. Ongoing melt percolation in the reservoir accumulates a new magma layer and the process repeats. Our results suggest that buoyancy, rather than crystallinity, is the key control on magma delivery from the source reservoir. They identify an optimum reservoir size for the largest silicic eruptions that is consistent with data from natural systems and explain why larger magnitude eruptions are not observed on Earth.

Rapid mapping of volcanic eruption building damage: A model based on prior knowledge and few-shot fine-tuning

Large-scale volcanic eruptions always inflict severe damage upon facilities and cause significant environmental pollution. Building damage caused by lava flow and volcanic ash coverage can reflect the infrastructure devastation and victim scope within the affected region. The application of machine learning methods for building damage automated identification from remote sensing imagery typically relies on a large number of training samples. However, labeled data scarcity is a common issue in the field of disasters, particularly in volcanic eruptions. To address this, we propose a two-stage building damage quick mapping workflow, which combines a building localization model trained on prior knowledge and a damage classification model fine-tuned on few-shot volcanic eruption-related samples. The classification model utilizes a CNN-based Siamese network for bi-temporal image feature extraction and comparison, with the backbone initialized with pre-trained weights from ImageNet. We conducted building damage classification tasks for single-disaster scenarios and cross-disaster domain scenarios in the eruptions of Mount Semeru, Tonga, and ST. Vincent; the visual damage level of each building was used as ground truth. The results demonstrate that our model can identify building damage efficiently and accurately in different volcanic eruption scenarios, with an over 93% F1-score on the 2-way 20-shot tasks. Furthermore, though building samples from different volcanic eruption regions present cross-domain challenges, our model can adapt to different feature domains by being supplemented with a few samples of another volcanic eruption disaster. Additionally, in the case of Mount Semeru Eruption, we gain insights into the potential of building damage statistics in post-eruption environmental assessments. To further enhance the model robustness on mixed-domain samples and multi-level damage classification tasks, issues including sample bias of certain disaster sources should be addressed.

Dying in the Sun: Direct evidence for elevated UV-B radiation at the end-Permian mass extinction

Land plants can adjust the concentration of protective ultraviolet B (UV-B)-absorbing compounds (UACs) in the outer wall of their reproductive propagules in response to ambient UV-B flux. To infer changes in UV-B radiation flux at Earth's surface during the end-Permian mass extinction, we analyze UAC abundances in ca. 800 pollen grains from an independently dated Permian-Triassic boundary section in Tibet. Our data reveal an excursion in UACs that coincide with a spike in mercury concentration and a negative carbon-isotope excursion in the latest Permian deposits, suggesting a close temporal link between large-scale volcanic eruptions, global carbon and mercury cycle perturbations, and ozone layer disruption. Because enhanced UV-B radiation can exacerbate the environmental deterioration induced by massive magmatism, ozone depletion is considered a compelling ecological driver for the terrestrial mass extinction.

Measuring air pollution from the 2021 Canary Islands volcanic eruption

The eruption of the Cumbre Vieja volcano on the island of La Palma (Canary Islands, Spain) began on September 19, 2021 and ended on December 13, 2021. It lasted continuously for 85 days with short periods of calm when lava did not exit the cone of the volcano. Vast amounts of volcanic material, including ash and gases, were emitted into the environment. This research focuses on these emissions. The main objective is to use available open-source data to examine the impact on regional and local air quality. Data from the following sources were used: 1) Copernicus Atmosphere Monitoring Service (CAMS) data was used to track the transfer of volcanic SO2 in the troposphere in early October over long distances from the source of the eruption, including Western and Eastern Europe, across the Atlantic Ocean and the Caribbean; 2) Data from ground monitoring stations measured the concentrations of SO2 and PM10 near the source; 3) AErosol RObotic NETwork (AERONET) data from the La Palma station that showed high Aerosol Optical Depth (AOD) values (over 0.4) during the active phase of emissions on September 24 and 28, as well as on October 3; 4) Ångström Exponent (AE) values indicated the presence of particles of different sizes. On September 24, high AE values (>1.5), showed the presence of fine-mode fraction scattering aerosols such as sulfates; 5) Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data additionally confirmed the presence of sulfate and dust aerosols in the atmosphere over the region. However, the influence of Saharan dust on the atmosphere of the entire region could not be excluded. This research helps forecast air pollution resulting from large-scale volcanic eruptions and associated health risks to humans.

Types and Eruption Patterns of the Carboniferous Volcanic Edifices in the Shixi Area, Junggar Basin

The types of volcanic edifices and volcanic eruption patterns control the accumulation and distribution of oil and gas. By means of drillings, seismic data, and geochemical analysis, the types and distribution of the Carboniferous volcanic edifices in the Shixi area of Junggar Basin were studied, the formation mechanism of magma was clarified, and the eruption patterns of volcanoes were investigated. The results show that the types of the Carboniferous volcanic edifices in the Shixi area mainly include stratovolcanic edifices, shield basic volcanic edifices, and mound superimposed volcanic edifices. Stratovolcanic edifices and mound superimposed volcanic edifices are developed around the Shixi fault, while single stratovolcanic edifices are developed around the Mobei fault. Shield basic volcanic edifices are only developed in the south of the Shixi area. Vertically, volcanic edifices are mainly developed on the hanging walls of the faults. When the faults develop, the volcanic vents are dendritic, forming mound superimposed volcanic edifices in space. On the plane, there are more volcanic edifices in the Shixi salient than in the Mobei salient. Intermediate-acid volcanic edifices are distributed in beaded shapes along one side of the Shixi fault and the Mobei fault, while basic volcanic edifices are distributed in sheet shapes on both sides of the Dinan fault. In the early Carboniferous, the Shixi area was in the island arc environment under the subduction of the oceanic crust. The basic magma came from the melting of the subduction plate, and the intermediate-acid magma came from the partial melting of the crust. In the late Carboniferous, the extensional environment formed by the retraction of the subduction plate led to the formation of large-scale volcanic eruptions. The extensional environment formed by the retreat of the subduction plate in the later stage resulted in large-scale volcanic eruptions.

The longtime global climatic consequences modeling of the Chicxulub asteroid impact event

Studies indicate the mass death of a significant number of biological groups on Earth, in particular - dinosaurs, at the end of the Cretaceous period 66 million years ago. Currently, there are two main theories: large-scale volcanic eruptions and the asteroid impact that formed the Chicxulub crater (Mexico). The production of sulfur-containing gases from the Earth’s surface layers vapors during impact is considered a main source of climatic effects, as they form stratospheric sulfate aerosols that block sunlight and thus cool the Earth’s atmosphere and interfere with photosynthesis. It is presented an application of the 3-D coupled global hydrodynamic climate model of intermediate complexity, including ocean model, sea ice evolution model and energy - moisture balance atmosphere model to study this asteroid impact effects on the Earth’s climate. The model continents and ocean depths distribution corresponds to Cretaceous period. A series of calculations with different residence times and deposition times of the stratosphere aerosol have been carried out. It was found that, depending on the stratosphere aerosol time parameters, the global annual average surface air temperature decreased by 18°C - 27°C, remained below zero for 4 - 30 years, and a recovery time of more than 30 years was observed.

Extreme climate historical variation based on tree-ring width record in the Tianshan Mountains of northwestern China.

The increasing frequency and intensity of extreme climate events have caused serious impacts on the service functions of terrestrial ecosystems and the production and life of human society in recent years. The warm nights (TN90p) variable of the 26 extreme climate indicators was the main factor controlling the tree radial growth of Schrenk spruce (Picea schrenkiana) in the Tianshan Mountains region based on the responses of tree-ring width in the 5 sample sites. Therefore, TN90p in the growth season from May to September (TN90p5-9) during 1735-2016 was reconstructed on the basis of the time stability of the growth-climate relationships. The interpretation rate of variance of the reconstructed equation was 45.4% (R2adj = 44.4%, F = 45.7). The reconstruction showed four relatively high TN90p5-9 historic intervals (1747-1798, 1856-1872, 1906-1951, and 2002-2016) and four low intervals (1735-1747, 1798-1856, 1872-1900, and 1951-2002). The occurrence frequency of extreme high values was higher than that of extreme low values during the reconstruction period of 1735-2016. The extreme values of reconstruction were consistent with historical droughts and large-scale volcanic eruptions, indicating that the reconstruction series had high accuracy. Multi-window spectral periodic analysis and spatial correlation analysis revealed that TN90p5-9 variation in the study area was affected by large-scale sea-air stress factors. In particular, the TN90p5-9 obtained by using R/S analysis (rescaled range analysis) will continue to show an upward trend in the relative period of time in the future. This trend will lead to a further decrease in the radial growth of trees and even trigger forest death events.

ITALIAN GEOLOGY AND CLIMATE CHANGE IN THE DEEP PAST

Mesozoic sedimentary rocks, of both deep- and shallow-water character, are present throughout Italy and well exposed in mountains and river valleys. Detailed studies of these sections by Italian geologists, beginning in the nineteenth century and continuing to this day, have produced a high-resolution biostratigraphy that allows identification of increments of geological time of less than a million years. Early work relied largely on ammonites to define biostratigraphy but was applicable primarily to sediments of Jurassic age. Study of deep-marine pelagic limestones and shales of Cretaceous age were subsequently, in the twentieth century, investigated using planktonic microfossils, the size of a sand grain, and even smaller nannofossils of micron scale. Pioneering work on magnetostratigraphy and cyclostratigraphy, undertaken primarily on Cretaceous sediments cropping out in Marche-Umbria, added further refinement to the measuring of small intervals of time in rock. With this stratigraphic background, distinct lithological and chemical signals, discovered first in Italian sequences, could be recognized world-wide and proven to be of global significance. In particular, the involvement of carbon isotopes has underscored the utility of chemostratigraphy, not only as a further aid to correlation, but also as a testimonial to major environmental change. Most significant in this context are the Cretaceous oceanic anoxic events, whose sedimentary record was first documented from Italy. These events were characterized by the development of organic-rich black shales deposited in waters largely lacking in oxygen during times of extraordinarily high temperatures known as hyperthermals. Hyperthermals, likely driven by supply of carbon dioxide from large-scale volcanic eruptions, illustrate the environmental impact on a planet affected by extreme global warming.

Mineralization zoning of coal-metal deposits in China

Substantive progress has been made in extracting germanium, gallium, rare earth elements (REEs), lithium, and other metals from coal. Coal deposits are becoming important sources of many strategic metal resources. However, ore deposit theory study for coal-metal resources has not been systematic. This paper summarizes the mineralization characteristics of germanium, gallium, lithium, and REEs in coal on the basis of previous research results and field investigations, including those on seven metallogenic zones of coal metal deposits in China. Coal-germanium deposits, products of magmatic hydrothermal activity, mainly occur in low rank coal in the areas of Erlian, the Hailaer Basin, Inner Mongolia, and the Sanjiang district in the Yunnan Province. Occasionally, rich-germanium-coal can be found in other areas. Coal-gallium deposits are mainly in the Permian coal of North China, Jurassic coal of Northwest China, and late-Permian coal of South China. The accumulation of gallium in coal is closely related to aluminum-containing minerals. Coal-lithium deposits mainly occur in the Zhungeer coal field, Inner Mongolia, the Pingshuo coal field, and the Jingcheng coal field in the Shanxi Province, and some coal fields in South China. Similarly to gallium, the accumulation of lithium in coal is also closely related to aluminum-containing minerals. Coal-REE deposits mainly occur in the Early Jurassic coal of the Erlian Basin and Inner Mongolia, and Late Permian coal in South China. REEs of Erlian basin coal likely entered in ionic forms in early stages of coal or peat bog formation. REEs of South China coal are likely associated with REE-rich trass volcanic ash which deposited synchronously with peat bog accumulation. Abundant abnormal metal elements in coal are important for classification of metallogenic zones. Regional tectonic background and evolution, characteristics of stratigraphic sedimentary environment, and coal quality are also important factors. (1) Delineation of germanium metallogenic zones in the coal follows the principles that: coal in the coal area should be low-metamorphic bituminous (long-flame) coal; the basement of the coal-bearing basin was broken and faults developed in the region; and there are obvious traces of hydrothermal intrusion in or around the coal measures in the zone. (2) Delineation of gallium metallogenic zones in coal is based on these traits: an obvious gallium source should exist in the region; the provenance area has favorable weathering and denudation conditions; and an aluminum-gallium formation under strong leaching is contained within. (3) Delineation of lithium metallogenic zones in coal requires: relatively clear sources of lithium in the zones; favorable weathering and denudation conditions in the provenance area; and aluminum-lithium containing rocks under strong leaching. (4) Delineation of rare earth mineralization zones in coal is based on: large scale volcanic eruptions in or near peat bogs during the accumulation period, with tuff in the coal-bearing strata; and hydrothermal intrusion into coal-measure strata during the peat bog period or early coal-forming period. According to the principles above, seven coal-metal metallogenic zones were identified, including: (1) the Erlian Basin-Hailaer Basin coal-germanium and REE deposit zone; (2) the Tianshan coal-gallium deposit zone; (3) the South-Yinshan coal-gallium-lithium deposit zone; (4) the East-Taihang Mountain coal-gallium deposit zone; (5) the Qilian-Qinling coal-gallium-lithium deposit zone; (6) the Sichuan-Yunnan-Guangxi coal-gallium-lithium and REE deposit zone; and (7) the Sanjiang (west Yunnan Province) germanium deposit zone.

Characteristics of clay deposits in Saga Plain, Japan

The characteristics of clay soil in the Saga Plain in Japan, as well as the effect of the depositional environment on its engineering properties, have been investigated. While the clay was being deposited there were several large-scale volcanic eruptions in the region. A considerable amount of volcanic ash settled into the clay, which had a marked effect on its engineering properties. The soil is strongly structured and the sedimentation compression curves are well above the sedimentation compression line proposed by Burland, which indicates some degree of cementation. The compression index is high – even for soil samples with in situ vertical effective stresses of 200–300 kPa, the index can be as high as 2·3. The rate of permeability reduction with void ratio is higher than most reported data in the literature. The reason considered is that the compression process involves not only gradual compression of the pores but also breaks down relatively large pores into smaller pores, which can cause rapid reduction of permeability. The stiffness is lower, with results of unconfined compression tests showing that the ratio of undrained shear strength to secant modulus is about 150.

A global review of Permian macrofloral biostratigraphical schemes

AbstractSeparate biostratigraphical schemes have been developed for Permian macrofloras in the five main phytochoria (palaeokingdoms), reflecting the essential lack of overlap in taxonomic composition. In Europe two biozones are normally recognized, in North America three zones, in Cathaysia three or four zones, in Gondwana four zones and in Angara five zones. The stratigraphical resolution tends to be far less than that of palynology, and up to an order of magnitude coarser than the macrofloral biozones of the Pennsylvanian subsystem. This is probably due, at least in part, to the lack of rigor in the way that the Permian macrofloral zones have been defined. Nevertheless, the existing zones do provide evidence of the overarching trajectory of change in vegetation through the Permian Period, as it responded at all palaeolatitudes to a combination of climate change, large-scale volcanic eruptions and tectonically driven landscape changes.

Volcanic Ash and Daily Mortality in Sweden after the Icelandic Volcano Eruption of May 2011

In the aftermath of the Icelandic volcano Grimsvötn’s eruption on 21 May 2011, volcanic ash reached Northern Europe. Elevated levels of ambient particles (PM) were registered in mid Sweden. The aim of the present study was to investigate if the Grimsvötn eruption had an effect on mortality in Sweden. Based on PM measurements at 16 sites across Sweden, data were classified into an ash exposed data set (Ash area) and an unexposed data set (No ash area). Data on daily all-cause mortality were obtained from Statistics Sweden for the time period 1 April through 31 July 2011. Mortality ratios were calculated as the ratio between the daily number of deaths in the Ash area and the No ash area. The exposure period was defined as the week following the days with elevated particle concentrations, namely 24 May through 31 May. The control period was defined as 1 April through 23 May and 1 June through 31 July. There was no absolute increase in mortality during the exposure period. However, during the exposure period the mean mortality ratio was 2.42 compared with 2.17 during the control period, implying a relatively higher number of deaths in the Ash area than in the No ash area. The differences in ratios were mostly due to a single day, 31 May, and were not statistically significant when tested with a Mann-Whitney non-parametric test (p > 0.3). The statistical power was low with only 8 days in the exposure period (24 May through 31 May). Assuming that the observed relative differences were not due to chance, the results would imply an increase of 128 deaths during the exposure period 24–31 May. If 31 May was excluded, the number of extra deaths was reduced to 20. The results of the present study are contradicting and inconclusive, but may indicate that all-cause mortality was increased by the ash-fall from the Grimsvötn eruption. Meta-analysis or pooled analysis of data from neighboring countries might make it possible to reach sufficient statistical power to study effects of the Grimsvötn ash on morbidity and mortality. Such studies would be of particular importance for European societies preparing for future large scale volcanic eruptions in Iceland.

Formation and timing of the extensional ductile shear zones in Yiwulü Mountain area, Western Liaoning Province, North China

The NNE-trending ductile shear zones in Yiwulu Mountain area were formed in relation to two successive extensional events. The Yiwulu High Temperature Extensional Ductile Shear Zone and the Waziyu Low Temperature Extensional Ductile Shear Zone were related to ductile deformation at higher temperatures and brittle-ductile deformation at lower temperatures, respectively. Both deformations were accompanied by large scale volcanic eruptions and magmatic intrusions. Based on structural analysis of macroscopic and microscopic deformations, and quartz lattice preferred orientations, we show that the early Yiwulu High Temperature Extensional Ductile Shear Zone was resulted from a NE-SW extension at amphibolite facies in the middle crust, whereas the Waziyu Low Temperature Extensional Ductile Shear Zone was due mainly to a NWW-SEE extension at greenschist facies in the upper crust. The SHRIMP zircon age of a syn-tectonic granitic dike emplaced at the late stage of high temperature extension is 155±2 Ma, indicating that the early extensional event took place in the Middle-Late Jurassic. 40Ar-39Ar age of muscovite from tectonic schists in the low temperature extensional ductile shear zone is 131.6±1.0 Ma, suggesting that the late extension occurred in the Early Cretaceous. Subsequent overall uplifting succeeded the late extension. The new discovery of the Middle-Late Jurassic NNE-trending extensional ductile shear zone provides evidence constraining the switch of tectonic regimes and Middle Jurassic thinning of lithosphere in the eastern North China Craton.

Dating of the Dome Fuji shallow ice core based on a record of volcanic eruptions from AD 1260 to AD 2001

We measured the concentration of non-sea-salt sulfate ( nssSO 4 2 − ) in the Dome Fuji shallow ice core (Antarctica) from the surface to 40 m depth with the aim of dating the core with reference to the record of volcanic eruptions. Three huge spikes related to large-scale volcanic eruptions were detected at depths of 12.5, 29.9, and 38.8 m, correlated to the eruptions of Tambora (AD 1815), Kuwae (AD 1452) and an unknown event (AD 1259), respectively. We identified another nine nssSO 4 2 − spikes related to accurately dated eruption events. The shallow ice core was dated from AD 1260 to AD 2001 based on these 12 eruption events and the assumption of constant annual snow accumulation in the periods between eruption events. The results yield a maximum correction of ∼20 years compared with the dating proposed in a previous study. The annual accumulation varied within ±∼15% of the average water equivalent value over the study period (25.5 mm).

Atmospheric Pressure Waves Generated from Large Earthquakes, Tsunamis and Large Volcanic Eruptions

This report reviews various studies on atmospheric pressure waves that have been generated from large earthquakes, tsunamis, and large-scale volcanic eruptions. These waves described here include low-frequency acoustic and gravity waves (0.0008∼0.0166 Hz or its period 1∼20 min) and high to medium frequency (› 0.0166 Hz or its period ‹ 1 min) infrasonic air-waves. The low-frequency acoustic-gravity waves came from coseismic vertical ground deformation associated with two megathrust earthquakes, and sometimes from other large earthquakes and volcanic eruptions, which propagated to more than several thousand kilometers through the lower to part of the upper atmosphere. The waves that reached the upper atmosphere could cause traveling ionospheric disturbances and perturbations of total electron content. The higher frequency infrasounds also have often been observed after large earthquakes and volcanic eruptions, which traveled as air-waves propagating directly from the source, and also as air-waves coupled with traveling seismic Rayleigh waves. Small atmospheric perturbations have also been detected during propagation of tsunami waves caused secondarily by large submarine earthquakes. Theoretical waveform modeling has been made in some of the above cases, incorporating a realistic atmospheric temperature structure. It is expected that more detailed information about the source process of large earthquakes and volcanic eruptions could be extracted through the analysis of the waveforms recorded at a number of stations, including their maximum amplitudes, wave frequencies, duration times, directions of wave approach, and phase and group velocities.

Explosive volcanic eruptions triggered by cosmic rays: Volcano as a bubble chamber

Volcanoes with silica-rich and highly viscous magma tend to produce violent explosive eruptions that result in disasters in local communities and that strongly affect the global environment. We examined the timing of 11 eruptive events that produced silica-rich magma from four volcanoes in Japan (Mt. Fuji, Mt. Usu, Myojin-sho, and Satsuma-Iwo-jima) over the past 306 years (from AD 1700 to AD 2005). Nine of the 11 events occurred during inactive phases of solar magnetic activity (solar minimum), which is well indexed by the group sunspot number. This strong association between eruption timing and the solar minimum is statistically significant to a confidence level of 96.7%. This relationship is not observed for eruptions from volcanoes with relatively silica-poor magma, such as Izu-Ohshima. It is well known that the cosmic-ray flux is negatively correlated with solar magnetic activity, as the strong magnetic field in the solar wind repels charged particles such as galactic cosmic rays that originate from outside of the solar system. The strong negative correlation observed between the timing of silica-rich eruptions and solar activity can be explained by variations in cosmic-ray flux arising from solar modulation. Because silica-rich magma has relatively high surface tension (~ 0.1 Nm −1), the homogeneous nucleation rate is so low that such magma exists in a highly supersaturated state without considerable exsolution, even when located relatively close to the surface, within the penetration range of cosmic-ray muons (1–10 GeV). These muons can contribute to nucleation in supersaturated magma, as documented by many authors studying a bubble chamber, via ionization loss. This radiation-induced nucleation can lead to the pre-eruptive exsolution of H 2O in the silica-rich magma. We note the possibility that the 1991 Mt. Pinatubo eruption was triggered by the same mechanism: an increase in cosmic-ray flux triggered by Typhoon Yunya, as a decrease in atmospheric pressure results in an increase in cosmic-ray flux. We also speculate that the snowball Earth event was triggered by successive large-scale volcanic eruptions triggered by increased cosmic-ray flux due to nearby supernova explosions.

Experiments on Mixotrophic Protists and Catastrophic Darkness

Catastrophically darkened photic zone conditions in water bodies are postulated to be induced by a diversity of mechanisms that are recorded in the geological record, including asteroid and comet impacts and large-scale volcanic eruptions. Giant wildfires, such as those that followed the great fires in Siberia in 1915, have been directly shown to cause large reductions in sunlight penetrating to the ground. Previous studies on the response of phototrophs to sudden prolonged darkness have focused on the survival of axenic strains. In this paper, we describe laboratory experiments to investigate the survival and growth of isolated and mixed cultures of freshwater and marine mixotrophs after 6 months of darkness and in the low light that would follow these events. Mixotrophs could survive 6 months of darkness. Some species used dissolved organic carbon, which can be released from dead biomass after loss of light and was shown to improve feeding rates. Mixotrophs also improved the survival and subsequent growth of obligate phototrophs at low light levels when grown in mixed cultures. The ability of mixotrophs to switch from photosynthesis to heterotrophy following sudden darkening would not only allow them to survive but to grow and contribute to active food chains. The experiments suggest that, following the return of light, resumption of photosynthesis can be rapid. These experiments improve our understanding of the collapse of photosynthesis following catastrophic darkening and emphasize the important role of mixotrophy in the resilience of the photosynthetic biosphere during such periods. We speculate on the implications for the Cretaceous-Tertiary impact event and periods of global freezing.

Climate modelling of mass-extinction events: a review

AbstractDespite tremendous interest in the topic and decades of research, the origins of the major losses of biodiversity in the history of life on Earth remain elusive. A variety of possible causes for these mass-extinction events have been investigated, including impacts of asteroids or comets, large-scale volcanic eruptions, effects from changes in the distribution of continents caused by plate tectonics, and biological factors, to name but a few. Many of these suggested drivers involve or indeed require changes of Earth's climate, which then affect the biosphere of our planet, causing a global reduction in the diversity of biological species. It can be argued, therefore, that a detailed understanding of these climatic variations and their effects on ecosystems are prerequisites for a solution to the enigma of biological extinctions. Apart from investigations of the paleoclimate data of the time periods of mass extinctions, climate-modelling experiments should be able to shed some light on these dramatic events. Somewhat surprisingly, however, only a few comprehensive modelling studies of the climate changes associated with extinction events have been undertaken. These studies will be reviewed in this paper. Furthermore, the role of modelling in extinction research in general and suggestions for future research are discussed.

The influence of volcanism on paleoclimate in the northeast of China: Insights from Jinchuan peat, Jilin Province, China

Just like contemporary sediments, peat itself is a good repository of information about climate change, the effects of volcanic activity on climate change have been truly recorded in peat, since it is a major archive of volcanic eruption incidents. A section of sand was identified as tephra from the Jinchuan peat, Jilin Province, China, for the grains look like slag with surface bubbles and pits, characterized by high porosity, and loose structure with irregular edges and corners. According to the peat characteristics of uniform deposition, the tephra was dated at 2002–1976 a B.P. by way of linear interpolation, so the time of volcanic eruption was 15 B.C.–26 A.D. (the calibrated age). While the geochemical characteristics of tephra in this study are quite the same as those of tephra from the Jinlongdingzi volcano at Longgang and from alkaline basaltic magma, with the contents of SiO2 K2O. We speculated that the tephra in this study came from the Longgang volcano group. Compared with 11 recorded volcanic eruption events as shown on the carbon and oxygen isotope curves of the Jinchuan peat cellulose, it is obviously seen that adjacent or large-scale volcanic eruptions are precisely corresponding to the minimum temperature and humidity. It seems that these volcanic eruptions indeed affected the local climate, leading to the drop of regional temperature and humidity. As a result, there was prevailing a cold and dry climate there, and all these changes can be well recorded in peat. So the comparison of volcanic eruption events with information about climate change developed from peat, can provide strong evidence for the impact of volcanism on climate change.

Updating channel morphology in digital elevation models: lahar assessment for Tenenepanco-Huiloac Gorge, Popocatépetl volcano, Mexico

In contrast to dramatic flow regime changes by less frequent large-scale volcanic eruptions, those caused by more frequent small-scale processes in volcanic landscapes may also drastically change the direction and dynamics of flow in a drainage system formed solely by fluvial processes. During such periods of channel morphology change, it is necessary to frequently update channel flow parameters to assess preventive measures for civil protection purposes. Often aerial photography is impracticable, since parts of the channels are covered by dense vegetation, while total station and laser topographic surveys are often too slow and costly, particularly during a high frequency of events. This article introduces and validates a new methodology for updating the representation of channel morphology in Digital Elevation Models (DEM) used specifically for assessing the dangers of frequently occurring lahars along gorges in volcanic landscapes during eruptive and non-eruptive periods. The updating of channel cross-sections was achieved by inserting more detailed representative profiles of homogeneous channel sectors in DEMs derived from existing less detailed topographic maps. The channel profiles were surveyed along the thalweg in equidistant points according to Universal Transverse Mercator (UTM) (x,y) coordinates and elevation derived from the existing DEM. The proposed technique was applied at Tenenepanco-Huiloac Gorge on Popocatepetl volcano, Mexico, in an area affected by major lahars during the volcano’s most recent eruptive period from 1994 to 2005. The proposed method can reduce the cost and person-hours of a regular channel topographic survey dramatically and the enhanced DEM can determine volume parameters and flood zones associated with the 1 July 1997 and 21 January 2001 lahars, respectively. In addition, the updated DEM with better channel representation allowed a more realistic fluid flow and lahar simulation with the process-based TITAN2D model.