Analysing Lava Risk for the Etnean Area: Simulation by Cellular Automata Methods     

Crisci  G. M.  Di Gregorio  S.  Rongo  R.  Spataro  W.  Nicoletta  F. 《Natural Hazards》1999,20(2-3):215-229

The model SCIARA, based on the Cellular Automata paradigm, is a versatile instrument whose scope is to analyse volcanic risk from lava flows.The possible fields of intervention are:[(a)] Long term forecasting of the flow direction at various eruption rates and points of emission by locating potential risk areas and permitting the creation of detailed maps of risk;[(b)] The possibility to follow the progress of an event and predict its evolution;[(c)] The verification of the possible effects of human intervention on real or simulated flows in stream deviation.A risk scenario has been developed for the Etnean territories of the towns of Nicolosi, Pedara and S. Alfio, simulating possible episodes with different vent locations along the fracture opened in the 1989 eruption and successively activated in the 1991–1993 eruption.The main characteristics of lava flows, that might be dangerous to the inhabited areas, have been analysed on the basis of the carried out Cellular Automata.  相似文献   

喀喇沁玻基橄辉岩中的磷酸盐质熔体及磷灰石   总被引：2，自引：0，他引：2  

邵济安  王志海 《岩石学报》2000,16(3):449-453

磷酸盐在本文讨论的坡基橄辉岩中以多种形式产生,有早期结晶的磷灰石斑晶;有熔离的磷酸盐质熔浆液滴;也有晚期穿入橄榄石斑晶的磷酸盐质细脉,表明元素磷活跃在岩浆演化的每一个阶段。磷酸盐质熔浆液滴的存在,说明磷酸盐质熔体可能是由于岩浆的熔离作用而形成的。沿着橄榄石晶格生长石出现的磷酸盐质玻璃细脉则进一步证实地幔中含磷流体不但存在,而且具有很强的活动性。  相似文献   

新疆西天山艾肯达坂组火山岩的地球化学特征     

姬红星 《物探与化探》2007,31(3):218-220

新疆西天山艾肯达坂组火山岩的岩石学和稀土元素的地球化学等研究证明，本区火山岩由基性火山岩和中性火山岩组成，火山岩均属于钙碱性系列，二者均具有低钾、富钠的特点。这些火山岩的稀土元素配分曲线均属于轻稀土富集型，明显地表现为轻稀土元素配分曲线陡倾，而重稀土元素配分曲线相对平坦的特征。这些岩石学和地球化学的特征证明本区火山岩形成于裂谷环境。  相似文献   

松辽盆地中央坳陷南部下白垩统泉头组四段沉积相   总被引：7，自引：0，他引：7  

张庆国  鲍志东  那未红  周新茂  孙继武 《古地理学报》2007,9(3):267-276

松辽盆地中央坳陷南部下白垩统泉头组四段沉积时期，松辽盆地地形平缓，基底沉降缓慢，在湖平面整体扩张及浅水背景下河流入湖成三角洲沉积。通过岩心观察、相标志与测井相研究，该区储层主要为岩屑长石砂岩和长石岩屑砂岩，识别出三角洲平原、三角洲前缘、前角洲3种亚相，以及分支河道、天然堤、决口扇、分支河道间湾、水下分支河道、水下决口扇、河口坝、远沙坝、水下分支河道间湾9种微相三角洲平原、三角洲前缘广泛发育，前三角洲不发育。三角洲平原分支河道通过填积和频繁的分叉改道，向湖盆中心方向长距离推进，在三角前缘的浅水区域发育了大量水下分支河道，分支河道与水下分支河道砂体相互切割、叠加，形成了平均宽度200~600 m、平均厚度3~8 m的道单砂体，（水下）分支河道砂体构成了油气富集的主要储集体。该区沉积相的精细研究，为进一步调整开发井网奠定了基础。  相似文献   

湖平面升降对浅水三角洲前缘砂体形态的影响   总被引：7，自引：4，他引：3  

楼章华  蔡希源 《沉积学报》1998,16(4):27-31

三角洲平原上的分流河道通过填积和湖面的频繁波动向湖泊中心方向长距离推进,在浅水三角洲前缘的浅水区发育很有特色的水下分流河道,且在湖面频繁波动过程中,河流、波浪和沿岸流的冲刷作用对沉积物分布起到再改造作用,导致了以水下分流河道砂体为主的三角洲前缘砂体不同程度的席状化。随着气候变得潮湿,湖面相对稳定,季节性、周期性湖面波动的频率、幅度减小,水动力对三角洲前缘砂体的改造和席状化强度减弱。  相似文献   

南京玄武湖水底交通隧道工程与环境效应分析     

倪宏革  李晓昭 《高校地质学报》1998,4(2):212-219

南京玄武湖隧道,既在城市中心,又在水下,是脆弱环境下典型的地质工程。影响水下隧道施工的不权有环境工程地质条件,还有城市环境约束因素;另外,隧道施工会对城市环境产生不良影响。作者对上述问题作了具体分析,并用系统工程的思想对隧道出口及施工方案的选择进行了初步评价。  相似文献   

廊固凹陷近岸水下扇特征及控制因素   总被引：2，自引：0，他引：2  

宋荣彩  张哨楠  董树义  周文 《地球科学与环境学报》2007,29(2):145-148,157

通过对廊固凹陷18口井541 m岩心的系统观察、156口井测井序列的建立、1km×1 km三维地震测网密度的地震相识别,分析了该沉积体系的相带展布特征。该砂砾岩层总体趋势为向上厚度减薄、层数减少,共识别出5期扇体,多呈条带状沿大兴断层断面分布,每期之间发育稳定的暗色泥岩段。该近岸水下扇的形成受3级层序、大兴断层、古构造、古气候、古地形以及物源供给等多种因素的控制。3级层序的发育特点、大兴断层的分段活动以及特殊的物源供给背景因素的匹配对近岸水下扇形成起到决定性作用。2~3期扇体扇中分布范围广,储集条件好,是凹陷下一步开发工作的有利目标。  相似文献   

Sedimentary evolution of the Holocene subaqueous clinoform off the southern Shandong Peninsula in the Western South Yellow Sea   总被引：1，自引：0，他引：1  

Jiandong Qiu  Jian Liu  Yoshiki Saito  Zigeng Yang  Baojing Yue  Hong Wang  Xianghuai Kong 《中国海洋大学学报(英文版)》2014,13(5):747-760

Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we addressed the sedimentary characteristics of a Holocene subaqueous clinoform in this paper. Integrated analyses were made on the core QDZ03, including sedimentary facies, sediment grain sizes, clay minerals, geochemistry, micro paleontology, and AMS 14 C dating. The result indicates that there exists a Holocene subaqueous clinoform, whose bottom boundary generally lies at 15–40 m below the present sea level with its depth contours roughly parallel to the coast and getting deeper seawards. The maximum thickness of the clinoform is up to 22.5 m on the coast side, and the thickness contours generally spread in a banded way along the coastline and becomes thinner towards the sea. At the mouths of some bays along the coast, the clinoform stretches in the shape of a fan and its thickness is evidently larger than that of the surrounding sediments. This clinoform came into being in the early Holocene(about 11.2 cal kyr BP) and can be divided into the lower and upper depositional units(DU 2 and DU 1, respectively). The unit DU 2, being usually less than 3 m in thickness and formed under a low sedimentation rate, is located between the bottom boundary and the Holocene maximum flooding surface(MFS), and represents the sediment of a post-glacial transgressive systems tract; whereas the unit DU 1, the main body of the clinoform, sits on the MFS, belonging to the sediment of a highstand systems tract from middle Holocene(about 7–6 cal kyr BP) to the present. The provenance of the clinoform differs from that of the typical sediments of the Yellow River and can be considered as the results of the joint contribution from both the Yellow River and the proximal coastal sediments of the Shandong Peninsula, as evidenced by the sediment geochemistry of the core. As is controlled mainly by coactions of multiple factors such as the Holocene sea-level changes, sediment supplies and coastal dynamic conditions, the development of the clinoform is genetically related with the synchronous clinoform or subaqueous deltas around the northeastern Shandong Peninsula and in the northern South Yellow Sea in the spatial distribution and sediment provenance, as previously reported, with all of them being formed from the initial stage of the Holocene up to the present.  相似文献   

A Miocene coarse volcaniclastic mass-flow deposit in the Shimane Peninsula,SW Japan: product of a deep submarine eruption?     

Kazuhiko Kano 《Bulletin of Volcanology》1996,58(2-3):131-143

 A subaqueous volcaniclastic mass-flow deposit in the Miocene Josoji Formation, Shimane Peninsula, is 15–16 m thick, and comprises mainly blocks and lapilli of rhyolite and andesite pumices and non- to poorly vesiculated rhyolite. It can be divided into four layers in ascending order. Layer 1 is an inversely to normally graded and poorly sorted lithic breccia 0.3–6 m thick. Layer 2 is an inversely to normally graded tuff breccia to lapilli tuff 6–11 m thick. This layer bifurcates laterally into minor depositional units individually composed of a massive, lithic-rich lower part and a diffusely stratified, pumice-rich upper part with inverse to normal grading of both lithic and pumice clasts. Layer 3 is 2.5–3 m thick, and consists of interbedded fines-depleted pumice-rich and pumice-poor layers a few centimeters thick. Layer 4 is a well-stratified and well-sorted coarse ash bed 1.5–2 m thick. The volcaniclastic deposit shows internal features of high-density turbidites and contains no evidence for emplacement at a high temperature. The mass-flow deposit is extremely coarse-grained, dominated by traction structures, and is interpreted as the product of a deep submarine, explosive eruption of vesicular magma or explosive collapse of lava. Received: 10 January 1996 / Accepted: 23 February 1996  相似文献   

长白山区二道白河流域早更新世玄武质熔岩的成因   总被引：2，自引：1，他引：1  

马晗瑞  杨清福  盘晓东  武成智  陈聪 《岩石学报》2015,31(11):3484-3494

采用岩石化学和同位素分析方法,研究了二道白河流域早更新世玄武质熔岩的成因。玄武质熔岩由钠质拉斑玄武岩和钾质粗面玄武岩、玄武质粗面安山岩组成。它们的REE分配形式比较相近,表明它们来自共同的源区。Sr、Nd、Pb同位素示踪表明,二道白河流域早更新世玄武质熔岩岩浆源区接近于似原始地幔。它们的Mg#=100Mg O/(Mg O+Fe O)低于中国东部新生代玄武岩原始岩浆的Mg#(60~68),Ni(27.76×10-6~200.6×10-6)低于原始地幔,Rb/Sr(0.05~0.09)、Ba/Rb(15.64~264)高于原始地幔,说明这些岩石不是源自原始地幔。玄武质熔岩的DI变化于42~67,具有高Ca、高Sr、Eu正异常,微量元素图解显示玄武岩保留部分熔融趋势,粗面玄武岩、玄武质粗安岩具有结晶分异趋势,岩浆上升过程中发生了不同程度的地壳混染作用。玄武质熔岩的Nb/Ta之比为14.8~15.8,与勘察加半岛深俯冲带火山类似。Nb/Ta-(Na2O-K2O)关系图解显示研究区玄武质岩浆的形成与俯冲板片的部分熔融有关。  相似文献