Morphological analysis of active Mount Nemrut stratovolcano, eastern Turkey: evidences and possible impact areas of future eruption     

Erkan Aydar  Alain Gourgaud  Inan Ulusoy  Fabrice Digonnet  Philippe Labazuy  Erdal Sen  Hasan Bayhan  Turker Kurttas  Arif Umit Tolluoglu 《Journal of Volcanology and Geothermal Research》2003,123(3-4):301-312

Mount Nemrut, an active stratovolcano in eastern Turkey, is a great danger for its vicinity. The volcano possesses a summit caldera which cuts the volcano into two stages, i.e. pre- and post-caldera. Wisps of smoke and hot springs are to be found within the caldera. Although the last recorded volcanic activity is known to have been in 1441, we consider here that the last eruption of Nemrut occurred more recently, probably just before 1597. The present active tectonic regime, historical eruptions, occurrence of mantle-derived magmatic gases and the fumarole and hot spring activities on the caldera floor make Nemrut Volcano a real danger for its vicinity. According to the volcanological past of Nemrut, the styles of expected eruptions are well-focused on two types: (1) occurrence of water within the caldera leads to phreatomagmatic (highly energetic) eruptions, subsequently followed by lava extrusions, and (2) effusions–extrusions (non-explosive or weakly energetic eruptions) on the flanks from fissures. To predict the impact area of future eruptions, a series of morphological analyses based on field observations, Digital Elevation Model and satellite images were realized. Twenty-two valleys (main transport pathways) were classified according to their importance, and the physical parameters related to the valleys were determined. The slope values in each point of the flanks and the Heim parameters H/L were calculated. In the light of morphological analysis the possible impact areas around the volcano and danger zones were proposed. The possible transport pathways of the products of expected volcanic events are unified in three main directions: Bitlis, Guroymak, Tatvan and Ahlat cities, the about 135 000 inhabitants of which could be threatened by future eruptions of this poorly known and unsurveyed volcano.  相似文献   

Genesis and distribution of mineral waters as a consequence of recent lithospheric dynamics: the Rhenish Massif,Central Europe     

Franz May  Stephan Hoernes  Horst J. Neugebauer 《International Journal of Earth Sciences》1996,85(4):782-799

Three major, interdependent processes control the genesis and distribution of mineral and thermal waters in the Rhenish Massif, Central Europe: (a) Magmatic processes in the upper mantle provide most of the CO₂ to produce bicarbonate waters in shallow aquifers. (b) Extension of the brittle upper crust enables the ascent of sodium chloride waters. (c) Uplift and erosion shape the massif's relief, which determines the extent of flow systems and the distribution of thermal springs. The chemistry of mineral waters further depends on the aquifers' mineral composition. A comprehensive set of hydrological, chemical, tectonic and geophysical data on the Rhenish Massif has been compiled. It was used to classify the mineral waters and to map the spatial distribution of water properties. The composition of cuttings from several representative wells producing different water types shows that the hydrothermal alteration of the aquifer rocks consists mainly of kaolinization of chlorite and dissolution of feldspar. Numerical transport simulations favour two modes of groundwater flow: topography-driven flow and the pressure-driven ascent of basement brines along active faults. Thermal convection is less important.  相似文献   

Observations of particle movement in a monitoring well using the colloidal borescope     

Peter M. Kearl 《Journal of Hydrology》1997,200(1-4):323-344

The colloidal borescope consists of a set of lenses and miniature video cameras capable of observing natural particles in monitoring wells. Based on field observations of these particles, it appears possible to measure in situ groundwater velocity in a well bore. Field observations have shown that directional measurements using the colloidal borescope are generally in good agreement with expected flow directions. However, the magnitude of flow velocity is higher compared with values based on conventional test methods. High relative flow velocities, even after correction factors have been applied to compensate for well bore effects, are believed to be due to preferential flow zones in the surrounding aquifer. Low flow zones exhibit swirling multidirectional flow that does not allow for a linear velocity measurement. Consequently, groundwater flow velocities measured by the colloidal borescope in heterogeneous aquifers will be biased toward the maximum velocity values present in the aquifer. A series of laboratory experiments was conducted to assess the reliability of the instrument. Based on this work, a seepage velocity correction factor ( ) of 1–4 was found for quantifying groundwater seepage velocity in the adjacent aquifer from observations in a well bore. Laboratory measurements also indicate that preferential flow in the surrounding aquifer dominates flow in the well. Results of this work suggest the possibility of quantifying higher-flow velocities associated with preferential flow zones in the subsurface.  相似文献   

一种新的流动注射在线共沉淀技术的研究及应用     

邹海峰  姜桂兰  徐淑坤  方肇伦 《吉林大学学报(地球科学版)》1997,(4)

建立了应用流动注射在线共沉淀分离富集火焰原子吸收法测定天然水样中痕量铬的价态分析方法。利用铬（Ⅲ）在碱性条件下与氢氧化镧形成共沉淀而与共存离子分离并得到富集，沉淀不需过滤，直接用稀盐酸从编织反应器（ＫＲ）中溶解并洗脱下来，用原子吸收测定。本体系的浓集倍率２２，检出限（３σ）０．８μｇ／Ｌ，相对标准偏差（ｎ＝１１）２．７２％，用水标样考察，分析结果与推荐值相符。该方法成功地用于天然水中铬的快速测定。  相似文献   

川陕丁家林金矿区探矿权的评估   总被引：2，自引：0，他引：2  

张蜀冀  韩旭  杨栓海 《黄金地质》2004,10(1):71-75

为准确、客观估价丁家林金矿区探矿权价值，根据矿区地质报告中提交的储量级别、矿体控制程度和工程质量，确定了基础和可采储量、生产规模、矿山服务年限、贴现率、有关实物工作量等6项参数。综合运用贴现现金流量和重置成本法对探矿权进行评估，对达到详查程度的基础储量采用贴现现金流量法，控制程度低的资源量采用重置成本法，二者之和综合反映探矿权的价值。此方法适用于地质工作程度不均衡矿区的探矿权评估，贴现现金流量法要充分考虑储量的可信度和获利临界品位．重置成本法关键是准确确定有关的实物工作量。  相似文献   

Seepage driving effect on deformations of San Fernando dams   总被引：2，自引：0，他引：2  

Xiang Song Li  Haiyan Ming   《Soil Dynamics and Earthquake Engineering》2004,24(12):979-992

In the process of flow deformation of an earth dam, the seepage force inside the dam plays a role as a driving force. The seepage force acts just like the gravitational force in terms of pushing soils away from their original locations after liquefaction is triggered. This paper draws attention to this seepage driving effect by presenting a set of fully coupled finite element analyses on the well-known San Fernando dams, with the objective of evaluating the impact of this seepage effect. The results indicate that while this effect is always there, its practical significance depends on a number of factors. In the case of the upper San Fernando dam, which experienced a significant, but restricted, downstream movement during the 1971 earthquake, the seepage driving effect was indeed significant. On the contrary, for the lower dam, which failed and slid into the upstream reservoir during the same earthquake, this seepage effect was relatively less pronounced. The detailed results of the analyses reveal the likely mechanisms of failure and deformation of the two dams and the likely cause behind the difference between their responses during the earthquake.  相似文献   

A brief comparison of lava flows from the Deccan Volcanic Province and the Columbia-Oregon Plateau Flood Basalts: Implications for models of flood basalt emplacement   总被引：1，自引：0，他引：1  

Ninad R. Bondre  Raymond A. Duraiswami  Gauri Dole 《Journal of Earth System Science》2004,113(4):809-817

The nature and style of emplacement of Continental Flood Basalt (CFB) lava flows has been a matter of great interest as well as considerable controversy in the recent past. However, even a cursory review of published literature reveals that the Columbia River Basalt Group (CRBG) and Hawaiian volcanoes provide most of the data relevant to this topic. It is interesting to note, however, that the CRBG lava flows and their palaeotopographic control is atypical of other CFB provinces in the world. In this paper, we first present a short overview of important studies pertaining to the emplacement of flood basalt flows. We then briefly review the morphology of lava flows from the Deccan Volcanic Province (DVP) and the Columbia-Oregon Plateau flood basalts. The review underscores the existence of significant variations in lava flow morphology between different provinces, and even within the same province. It is quite likely that there were more than one way of emplacing the voluminous and extensive CFB lava flows. We argue that the establishment of general models of emplacement must be based on a comprehensive documentation of lava flow morphology from all CFB provinces.  相似文献   

Plastic flow strength of jadeite and diopside investigated by microindentation hardness tests     

Dorothe Dorner  Bernhard Stckhert 《Tectonophysics》2004,379(1-4):227-238

Microindentation hardness tests were performed on jadeite and diopside, being end members of the omphacite solid solution series. At temperatures between 300 and 750 °C, the hardness of jadeite ranges from 7.4 to 8.5 GPa, that of diopside from 4.9 to 6.1 GPa. Jadeite is significantly stronger than diopside in the low-temperature plasticity regime. Normalization of the hardness-derived yield stress with respect to the shear modulus considerably reduces the strength contrast. The normalized Peierls stress is identical for jadeite and diopside. This indicates that jadeite and diopside belong to the same isomechanical group. The hardness-derived yield stress for jadeite as well as for diopside is used to estimate flow law parameters for the low-temperature plasticity regime.  相似文献   

Dynamics of an active rock glacier (Ötztal Alps, Austria)     

Jana Berger  Karl Krainer  Wolfram Mostler 《Quaternary Research》2004,62(3):233-242

The rock glacier Innere Ölgrube, located in a small side valley of the Kauner Valley (Ötztal Alps, Austria), consists of two separate, tongue-shaped rock glaciers lying next to each other. Investigations indicate that both rock glaciers contain a core of massive ice. During winter, the temperature at the base of the snow cover (BTS) is significantly lower at the active rock glacier than on permafrost-free ground adjacent to the rock glacier. Discharge is characterized by strong seasonal and diurnal variations, and is strongly controlled by the local weather conditions. Water temperature of the rock glacier springs remains constantly low, mostly below 1°C during the whole melt season. The morphology of the rock glaciers and the presence of meltwater lakes in their rooting zones as well as the high surface flow velocities of >1 m/yr point to a glacial origin. The northern rock glacier, which is bounded by lateral moraines, evolved from the debris-covered tongue of a small glacier of the Little Ice Age with its last highstand around A.D. 1850. Due to the global warming in the following decades, the upper parts of the steep and debris-free ice glacier melted, whereas the debris-covered glacier tongue transformed into an active rock glacier. Due to this evolution and due to the downslope movement, the northern rock glacier, although still active, at present is cut off from its ice and debris supply. The southern rock glacier has developed approximately during the same period from a debris-covered cirque glacier at the foot of the Wannetspitze massif.  相似文献   

描述黄河中下游河道横断面形态的新指标     

孙赞盈  曲少军  苏运启  杨明 《山地学报》2004,22(2):161-164

描述河流横断面的窄深程度,无非是用来衡量它对过流能力和输沙能力的影响大小,及其在河流地貌方面的时空上的调整变化。回顾总结了以往描述横断面形态的常用指标,包括河相系数、宽深比,或湿周与平均水深的比值,指出这几种指标在描述黄河中下游河道时所存在的共同缺点:(1)缺乏物理意义;(2)不能真正代表断面的窄深程度;(3)明显的夸大了宽浅和窄深断面的差别。从表称流量的概念出发,作者认为,应该使用具有明确物理意义的等面积的表称流速来描述断面形态。如果用表称流速来衡量黄河下游河南和山东河道的断面形态的差别,就会发现,断面形态的不同,其对过流能力的影响不过1:2,远不象河相系数和宽深比所描述的达到1:6甚至1:11那样的悬殊程度;黄河下游河道主槽“多来多排”的主要影响因素是表称流速。  相似文献