47 research outputs found
Catastrophic avalanches and methods of their control
No full textDefinition of such phenomenon as “catastrophic avalanche” is presented in this arti-cle. Several situations with releases of catastrophic avalanches in mountains of Caucasus, Alps, and Central Asia are investigated. Materials of snow-avalanche ob-servations performed since 1960s at the Elbrus station of the Lomonosov Moscow State University (Central Caucasus) were used for this work. Complex-valued measures of engineering protection demonstrating different efficiencies are consid-ered
EXTREME WINTERS IN XX–XXI CENTURIES AS INDICATORS OF SNOWINESS AND AVALANCHE HAZARD IN THE PAST AND EXPECTED CLIMATE CHANGE CONDITIONS
No full textCurrently, due to the global climate change and increasing frequency of weather events focus is on prediction of climate extremes. Large-scale meteorological anomalies can cause long-term paralysis of social and economic infrastructure of the major mountain regions and even individual states. In winter periods, these anomalies are associated with prolonged heavy snowfalls and associated with them catastrophic avalanches which cause significant social and economic damage. The climate system maintains a certain momentum during periods of adjustment and transition to other conditions in the ratio of heat and moisture and contains a climate «signal» of the climates of the past and the future. In our view seasonal and yearly extremes perform the role of these indicators, study of which enables for a deeper understanding and appreciation of the real situation of the climate periods related to the modern ones. The paper provides an overview of the criteria for selection of extreme winters. Identification of extremely cold winters during the period of instrumental observation and assessment of their snowiness and avalanche activity done for the Elbrus region, which is a model site for study of the avalanche regime in the Central Caucasus. The studies aim to identify the extreme winters in the Greater Caucasus, assess their frequency of occurrence, characterize the scale and intensity of the avalanche formation. The data obtained can be used to identify winter-analogues in the reconstruction and long-term forecast of avalanches
Dynamics of nival and glacial slope processes in the Baksan and Teberda river basins from radiocarbon dating of buried soils
No full textRadiocarbon and tree-ring dating of the soil horizons, buried in the slope and fluvioglacial deposits in Baksan and Teberda valleys, bring evidence of the reduction of the avalanche activity, stabilization of the slopes and soil formation on their surfaces. In the Baksan section three such horizons are identified, while in the Teberda section only one. The radiocarbon dates of the two thickest soil horizons in the Baksan section are 170±50 BP (1650–1890 CE) and 380±60 BP (1430–1650 CE). The dendrochronological date of the wood (after 1677) in the upper layer of the buried soil horizon in the in the Dombai section probably indicate the increase of the river runoff and debris flow activity in relation with the glacier advance in the upperstream of Ammanauz river. However it is also close to the Terskoye earth quake occurred in 1688. The radiocarbon dates of the buried soils cluster in three groups (270–290, 340–440, 1280–1440 yrs BP). It is possible that their burial is connected to the climatic (increase in precipitation, especially extreme ones) or seismic causes
Recent trends of snow avalanche regime in the Central Caucasus (Elbrus region as an example)
Get PDFThe climate change during cold seasons of 1995–2017 in the Central Caucasus is estimated, and its influence on the avalanche regime is shown. Data on the avalanche releases in the Central Caucasus for the period 1968– 2017 together with observations of high-altitude meteorological stations were used for the analysis. The paper presents estimates of snowiness of the winters and their frequency of occurrence in the area under investigation. The winter snowiness was noted to decrease since the beginning of the 2000s. The last decade of the period was not snowy, especially its series of six winters having very small amounts of snow. It is shown that in the second half of the XX century the heaviest snowfalls took place mostly in Januaries, and they were followed by releases of avalanches with the volumes exceeding 1 million cubic metres. In the early 2000‑ies, intensive January snowfalls were observed later, i.e. during the winter-spring period. In the warmer months March and April, the destructive potential of avalanches was noticeably smaller. In the present time, the warming and decrease of winter snowiness resulted in significant diminution of the avalanche hazard in the region. At the same time, on the background of general warming the certain increase in inter-seasonal variability of air temperature was noted. These changes may be compared to the warming of 1910–1945 when during its warmest phase the Europe suffered with one of the harshest winters in 1941/42. The swing of the «temperature pendulum» indicates that a harsh winter with heavy snowfalls and avalanches with catastrophic consequences may occur on the background of winters with mild and moderate avalanche danger. This is one of probable scenarios in the development of avalanche activity in the Greater Caucasus in the context of the current climate change
Winters of avalanche maximum in the Greater Caucasus for the period of instrumental observations (1968–2016)
Get PDFThis investigation has been carried out to identify winters with the maximum frequency of avalanches in the Greater Caucasus. The analysis was performed for decades and for the entire period of instrumental observations (1968–2016). We chose severe snow winters which were followed by releases of particularly large and heavy avalanches (Lmax) and the maximum area of damage to the mountain territory during the study period. The following materials were used for this work: 1) 47‑year-old (1968–2016) series of data on snow avalanches from observations performed at the high-altitude station of the Faculty of Geography of the Lomonosov Moscow State University in the near-Elbrus area (Central Caucasus); 2) the results of winter and summer investigations of snow and avalanches in Arkhyz (the Western Caucasus); 3) materials of field works carried out in the Caucasus at different times; 4) the results of winter typing from data of 41 mid- and high-mountain meteorological stations in the Greater Caucasus; 5) literature sources; 6) survey data. The dependence of avalanche activity on the types of winters was established for key observational sites in the near-Elbrus area (Central Caucasus) and Arkhyz (Western Caucasus). This dependence formed the basis for determining the Lmax winters from factors of the avalanche formation, i.e. the air temperature and precipitation for the cold period from meteorological observations. Based on the method of winter typing, the winters of the maximal avalanche occurrence were estimated from data of 41 meteorological stations of the Greater Caucasus for 1936–2016. Results of the typing revealed similar avalanche extremes as it was found from direct observations of releases of snow avalanches: on the Southern macro-slope of the Western and Central Caucasus – 1986/87; on the Eastern Caucasus – 1971/72. Two seasons, claiming the role of the Lmax – 1967/68 and 1975/76, were revealed on the Northern macro-slope
Avalanche prevention release system GAZEX as a tool to control of snow discharge in small portions
No full textGAZEX system is used in Russia from 2002 to release artificial avalanches. The experience of realization of this system in the Krasnaya Polyana region (the place of Olympic Winter Games of 2014) is described in the article in comparison with application of nowadays and earlier systems
MORPHOFUNCTIONAL FEATURES OF VENTRICULAR ARRHYTHMIAS IN PATIENTS WITH POSTINFARCTION CARDIOSCLEROSIS AND ARTERIAL HYPERTENSION, DEPENDING ON THE AFFECTED CORONARY REGION
Get PDFAcute and chronic perfusion disorders, the presence of hypertension are among the main risk factors for the development of electrical instability of the myocardium, in particular ventricular arrhythmias (VA), the progressive course of which increases the risk of sudden cardiac death. Changes in a number of electro- and echocardiographic indicators are recommended to be considered as predictors of the development of life-threatening arrhythmias. Purpose of the study was to study VA features, myocardial remodeling processed and lipid metabolism in patients with arterial hypertension (AH) and myocardial infarction, depending on the affected coronary region. Material and methods. The study involved 50 patients 40–80 years old with post-infarction cardiosclerosis, AH, ventricular arrhythmias episodes, of which 25 people are patients with atherosclerotic lesions of left coronary artery (LCA), 25 people are with the lesions of right coronary artery (RCA). Exclusion criteria: dilated cardiomyopathy, decompensated valvular defects, arrhythmogenic dysplasia, idiopathic ventricular tachycardia, myocarditis. Research methods: echocardiography, coronary angiography, Holter monitor (24-Hour ECG monitoring), biochemical data. Results and discussion. The tendency to the presence of more pronounced pathological changes of heart rate turbulence due to an increase of turbulence slope, dominance of the sympathetic division of the autonomic nervous system against the background of a significantly larger number of paired ventricular extrasystoles have been revealed in the group of patients with atherosclerotic lesions of LCA. That reflects organic and functional changes in the myocardium. The absence of significant changes in the duration and dispersion of the QT interval of the compared groups confirmed the low informativeness of these criteria in the prediction of the VA. The significantly lower value of interventricular septum thickness, left ventricular myocardial mass, and larger size of the right ventricle (0.15 ms) have been revealed along with the above mentioned changes in the group due to the slightly different course of the AH, myocardial remodeling processes. However, more significant changes in the lipid profile, in particular an increase in the level of total cholesterol and blood triglycerides have been registered in the group of patients with PCA. Conclusion. The more pronounced pathological shift of heart rate turbulence due to the increase of turbulence slope up to 4.4 ms/RR on the background of more paired ventricular extrasystoles has been determined in the defeat of the LCA. The significantly lower value of interventricular septum thickness, left ventricular myocardial mass, and larger size of the right ventricular have been observed in the group of patients with atherosclerotic lesions of the LCA in comparison with group of patients with lesions of the PCA
PROBABILISTIC ZONING OF ADJACENT CATCHMENTS BY PHYSICAL MODELING
No full textNow the probabilistic zoning of avalanche sites is being made either on the basis of the available field data, or using the mathematical and physical modeling of avalanche dynamics processes. The work purpose consisted in research of interaction and compiling probabilistic zoning maps of two adjacent avalanche sites by a physical modeling method. For the two adjacent sites № 9 and 10 on the slope of northern exposition ofTchegetMountain(Elbrus region,Caucasus) the model of this slope with the scale of 1: 2 500 was created. The model dimension is 0,82 × 1,1 ×0,57 m. This model was produced using the 4-mm plywood sheets imposed against each other. The model horizontals correspond to the10 mnatural ones. The model slope was also surfaced by thin gypsum lay and then varnished. The fine-grained sawdust (0.1 mm) with a natural friction angle of 43º has been chosen as the loose material modeling snow. A series of experiments on modeling avalanche releases from the two sites were carried out resulted in the measurements of avalanche deposit parameters such as run-out distance and length, width and thickness of deposits. The similarity criteria were used during the experiments. The morphometric features of adjacent sites interaction are revealed. The basic result of the carried out work will consist in the probabilistic zoning map of two adjacent sites № 9 and 10
A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus
Get PDFThe glacier coverage in the Caucasus Mountains underwent considerable changes during the last decades. In some regions, the observed reduction in glacier area is comparable to those in the European Alps and the extent of supra-glacial debris increased on many glaciers. Only a few glaciers in the Caucasus are monitored on a regular basis, while for most areas no continuous field measurements are available. In this study, regional differences of the conditions for glacier melt with a special focus on debris covered glacier tongues in the well-studied Adyl-su basin on the northern slope of the Caucasus Mountains (Russia) is compared with the Zopkhito basin which has similar characteristics but is located on the southern slope in Georgia. The paper focuses on the effect of supra-glacial debris cover on glacier summer melt. There are systematic differences in the distribution and increase of the debris cover on the glaciers of the two basins. In the Adyl-su basin an extensive debris cover on the glacier tongues is common, however, only those glacier tongues that are positioned at the lowest elevations in the Zopkhito basin show a considerable extent of supra-glacial debris. The observed increase in debris cover is considerably stronger in the north. Field experiments show that thermal resistance of the debris cover in both basins is somewhat higher than in other glaciated regions of the world, but there is also a significant difference between the two regions. A simple ablation model accounting for the effect of debris cover on ice melt shows that melt rates are considerably higher in the northern basin despite a wider debris distribution. This difference between the two regions can be attributed to different meteorological conditions which are characterised by more frequent cloud cover and precipitation in the south. Furthermore ablation is strongly influenced by the occurrence of supra-glacial debris cover in both basins, reducing the total amount of melt on the studied glaciers by about 25 %. This effect mitigates glacier retreat in the lower sectors of the ablation zones considerably. The sensitivity to moderate changes in the debris cover, however, is rather small which implies only gradual changes of the melt regime due to debris cover dynamics during the near future
Age of moraines of the Bolshoy Azau Glacier in the upper course of the Baksan River valley according to dendrochronological data
Get PDFBasing on treering analysis of more than 150pines growing in the Azau clearing, the minimum age of the deposits created by the Greater Azau Glacier was identified. Historical evidence, cartographic data, remote sensing materials, as well as the results of lichenometric studies and radiocarbon dating of buried soils were used as additional sources of information. We determined limits of the area covered by the glacier tongue at the end of the 19th century. It was also shown that the highest and most pronounced lateral moraine, conventionally called the «17th century moraine», was formed earlier than the end of the 15th century. Judging from the size of the maximum lichens of Rhizocarpon geographicum (120–130mm) on its surface, the age of the moraine, determined by the dendrochronological method was found to be underestimated. It may be several centuries older than the end of the 16th century. We reexamined a pine trunk buried in the sediments at the bottom of the valley which was discovered in the 1960s. Previously it was dated by radiocarbon (140±75BP[1], the calibrated date– 1650–1960 CE). According to the new data, the most probable treering dates of the buried tree are 1759–1883CE, however, the second most likely dates are 1826–1950CE. Unfortunately, low statistical estimates do not allow us to confirm the reliability of the dates. The paper also discusses the controversial issue of the position of the moraine of 1849CE, which was described by H.Abich[2]. The annex to the article contains a translation of a fragment of this important paper related to the Greater Azau Glacier. Suppressions of pine growth from the moraines of the Greater Azau in the 1640s, 1710s, 1800s, 1840s, and 1860sCE are synchronous with the advances of the Bosson, Mer de Glace and Grindelwald glaciers in the Alps[3]
