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21.
B. Behncke S. Calvari S. Giammanco M. Neri H. Pinkerton 《Bulletin of Volcanology》2008,70(10):1249-1268
After 16 months of quiescence, Mount Etna began to erupt again in mid-July 2006. The activity was concentrated at and around
the Southeast Crater (SEC), one of the four craters on the summit of Etna, and eruptive activity continued intermittently
for 5 months. During this period, numerous vents displayed a wide range of eruptive styles at different times. Virtually all
explosive activities took place at vents at the summit of the SEC and on its flanks. Eruptive episodes, which lasted from
1 day to 2 weeks, became shorter and more violent with time. Volcanic activity at these vents was often accompanied by dramatic
mass-wasting processes such as collapse of parts of the cone, highly unusual flowage processes involving both old rocks and
fresh magmatic material, and magma–water interaction. The most dramatic events took place on 16 November, when numerous rockfalls
and pyroclastic density currents (PDCs) were generated during the opening of a large fracture on the SE flank of the SEC cone.
The largest PDCs were clearly triggered explosively, and there is evidence that much of the energy was generated during the
interaction of intruding magma with wet rocks on the cone’s flanks. The most mobile PDCs traveled up to 1 km from their source.
This previously unknown process on Etna may not be unique on this volcano and is likely to have taken place on other volcanoes.
It represents a newly recognized hazard to those who visit and work in the vicinity of the summit of Etna. 相似文献
22.
建立地震灾害损失评估数据库是以ILWIS和PCARC/INFOGIS软件为工作平台。它能支持矢量格式的专题图件、栅格形成的遥感数据及关系表中的属性数据;它还可以实现矢量-栅格转换;而且数据库中的属性数据作为一个独立的关系表格存贮,并对应于其相关的空间单元。该数据库是以1976年唐山地震的航空遥感资料为基础,主要分3步进行。第一:建立地震区的基础地理数据库,包括:地理坐标、河流水系、县级行政区、公路、铁路和居民点;第二:应用航空遥感数据(航空影象)进行震区建筑物倒毁、生命线工程破坏及场地震害的分类分级,建立地震灾害数据库;第三:在GIS支持下,生成高烈度区包络线,并进行地震灾害据失评估。 相似文献
23.
24.
The Commission on Geological Sciences for Environmental Planning (COGEOENVIRONMENT) of IUGS and UNESCO have initiated a joint
project to develop a worldwide data base on earth-science-related environmental problems and to assess which geoscientific
information is available locally for prevention, prediction or mitigation of such problems. As a first step, a pilot project
on geo-environmental problems and geo-information was launched for central and eastern Europe. In this paper the results of
a questionnaire sent to all these partly new countries are presented. Analysis of the results of the questionnaire shows that
the most serious and common geo-environmental problems in central and eastern Europe are earthquakes, landslides, soil contamination,
groundwater pollution and flooding by rivers. Other geo-environmental problems in this part of Europe and some difficulties
experienced during the pilot project are also referred to. Some suggestions for the application of geoscientific knowledge
to mitigate such problems are presented at the end of this paper.
Received: 25 February 1997 · Accepted: 28 January 1998 相似文献
25.
Claus?SiebeEmail author Virgilio?Rodríguez-Lara Peter?Schaaf Michael?Abrams 《Bulletin of Volcanology》2004,66(3):203-225
Pelado, Guespalapa, and Chichinautzin monogenetic scoria cones located within the Sierra del Chichinautzin Volcanic Field (SCVF) at the southern margin of Mexico City were dated by the radiocarbon method at 10,000, 2,800–4,700, and 1,835 years b.p., respectively. Most previous research in this area was concentrated on Xitle scoria cone, whose lavas destroyed and buried the pre-Hispanic town of Cuicuilco around 1,665±35 years b.p. The new dates indicate that the recurrence interval for monogenetic eruptions in the central part of the SCVF and close to the vicinity of Mexico City is <2,500 years. If the entire SCVF is considered, the recurrence interval is <1,700 years. Based on fieldwork and Landsat imagery interpretation a geologic map was produced, morphometric parameters characterizing the cones and lava flows determined, and the areal extent and volumes of erupted products estimated. The longest lava flow was produced by Guespalapa and reached 24 km from its source; total areas covered by lava flows from each eruption range between 54 (Chichinautzin) and 80 km2 (Pelado); and total erupted volumes range between 1 and 2 km3/cone. An average eruption rate for the entire SCVF was estimated at 0.6 km3/1,000 years. These findings are of importance for archaeological as well as volcanic hazards studies in this heavily populated region.Editorial responsibility: J. Gilbert 相似文献
26.
This article analyzes a political process in the aftermath of a disaster and explains why and how it led to maladaptation. Grounding Gramsci’s theory of the State on a case of post-disaster response to a fatal mudslide in the city of Sarno in Italy, this research argues that, under certain conditions, civil society and the ruling classes may coalesce to produce policies that are maladaptive. We unpack the mechanisms through which consent was reproduced in Sarno, and show how the claims of civil society were articulated and fused with the hegemonic goals of capital circulation and economic growth, reaffirming a view of government as only a provider of safety. A Gramscian treatment of the State as a process, and not as a thing, highlights that the main barrier to adaptation is not the lack of techno-managerial solutions. It is the lack of political struggle around the social reconfiguration of the logic and functions of the State. 相似文献
27.
Christopher F. Waythomas 《Bulletin of Volcanology》1999,61(3):141-161
Akutan Volcano is one of the most active volcanoes in the Aleutian arc, but until recently little was known about its history
and eruptive character. Following a brief but sustained period of intense seismic activity in March 1996, the Alaska Volcano
Observatory began investigating the geology of the volcano and evaluating potential volcanic hazards that could affect residents
of Akutan Island. During these studies new information was obtained about the Holocene eruptive history of the volcano on
the basis of stratigraphic studies of volcaniclastic deposits and radiocarbon dating of associated buried soils and peat.
A black, scoria-bearing, lapilli tephra, informally named the "Akutan tephra," is up to 2 m thick and is found over most of
the island, primarily east of the volcano summit. Six radiocarbon ages on the humic fraction of soil A-horizons beneath the
tephra indicate that the Akutan tephra was erupted approximately 1611 years B.P. At several locations the Akutan tephra is
within a conformable stratigraphic sequence of pyroclastic-flow and lahar deposits that are all part of the same eruptive
sequence. The thickness, widespread distribution, and conformable stratigraphic association with overlying pyroclastic-flow
and lahar deposits indicate that the Akutan tephra likely records a major eruption of Akutan Volcano that may have formed
the present summit caldera. Noncohesive lahar and pyroclastic-flow deposits that predate the Akutan tephra occur in the major
valleys that head on the volcano and are evidence for six to eight earlier Holocene eruptions. These eruptions were strombolian
to subplinian events that generated limited amounts of tephra and small pyroclastic flows that extended only a few kilometers
from the vent. The pyroclastic flows melted snow and ice on the volcano flanks and formed lahars that traveled several kilometers
down broad, formerly glaciated valleys, reaching the coast as thin, watery, hyperconcentrated flows or water floods. Slightly
cohesive lahars in Hot Springs valley and Long valley could have formed from minor flank collapses of hydrothermally altered
volcanic bedrock. These lahars may be unrelated to eruptive activity.
Received: 31 August 1998 / Accepted: 30 January 1999 相似文献
28.
Jean-Claude Thouret Marco Rivera Gerhard Wörner Marie-Christine Gerbe Anthony Finizola Michel Fornari Katherine Gonzales 《Bulletin of Volcanology》2005,67(6):557-589
Ubinas volcano has had 23 degassing and ashfall episodes since A.D. 1550, making it the historically most active volcano in southern Peru. Based on fieldwork, on interpretation of aerial photographs and satellite images, and on radiometric ages, the eruptive history of Ubinas is divided into two major periods. Ubinas I (Middle Pleistocene >376 ka) is characterized by lava flow activity that formed the lower part of the edifice. This edifice collapsed and resulted in a debris-avalanche deposit distributed as far as 12 km downstream the Rio Ubinas. Non-welded ignimbrites were erupted subsequently and ponded to a thickness of 150 m as far as 7 km south of the summit. These eruptions probably left a small collapse caldera on the summit of Ubinas I. A 100-m-thick sequence of ash-and-pumice flow deposits followed, filling paleo-valleys 6 km from the summit. Ubinas II, 376 ky to present comprises several stages. The summit cone was built by andesite and dacite flows between 376 and 142 ky. A series of domes grew on the southern flank and the largest one was dated at 250 ky; block-and-ash flow deposits from these domes filled the upper Rio Ubinas valley 10 km to the south. The summit caldera was formed between 25 and 9.7 ky. Ash-flow deposits and two Plinian deposits reflect explosive eruptions of more differentiated magmas. A debris-avalanche deposit (about 1.2 km3) formed hummocks at the base of the 1,000-m-high, fractured and unstable south flank before 3.6 ka. Countless explosive events took place inside the summit caldera during the last 9.7 ky. The last Plinian eruption, dated A.D.1000–1160, produced an andesitic pumice-fall deposit, which achieved a thickness of 25 cm 40 km SE of the summit. Minor eruptions since then show phreatomagmatic characteristics and a wide range in composition (mafic to rhyolitic): the events reported since A.D. 1550 include many degassing episodes, four moderate (VEI 2–3) eruptions, and one VEI 3 eruption in A.D. 1667. Ubinas erupted high-K, calc-alkaline magmas (SiO2=56 to 71%). Magmatic processes include fractional crystallization and mixing of deeply derived mafic andesites in a shallow magma chamber. Parent magmas have been relatively homogeneous through time but reflect variable conditions of deep-crustal assimilation, as shown in the large variations in Sr/Y and LREE/HREE. Depleted HREE and Y values in some lavas, mostly late mafic rocks, suggest contamination of magmas near the base of the >60-km-thick continental crust. The most recently erupted products (mostly scoria) show a wide range in composition and a trend towards more mafic magmas.Recent eruptions indicate that Ubinas poses a severe threat to at least 5,000 people living in the valley of the Rio Ubinas, and within a 15-km radius of the summit. The threat includes thick tephra falls, phreatomagmatic ejecta, failure of the unstable south flank with subsequent debris avalanches, rain-triggered lahars, and pyroclastic flows. Should Plinian eruptions of the size of the Holocene events recur at Ubinas, tephra fall would affect about one million people living in the Arequipa area 60 km west of the summit.Editorial responsibility: D Dingwell 相似文献
29.
云南省泥石流灾害区域特征调查与分析 总被引:9,自引:3,他引:9
唐川 《云南地理环境研究》1997,9(1):1-9
本文根据对云南省2000条泥石流沟的调查,综合分析了全省泥石流形成的区域环境背景条件,阐述了泥石流危害现状和对我省社会、经济的影响,分析了云南省泥石流灾害活动规律和区域分布特征,为全省泥石流灾害区域预测预报和综合治理提供了科学依据。 相似文献
30.
本文认为环境岩土工程问题与污染和生态破坏环境问题是等价的。所以,存在着两类同样重要的环境问题。关于两类环境问题的类型划分和内容,文中做了系统介绍和讨论。并着重对我国东部3个有重要意义的主要环境岩土工程问题进行了分析。 相似文献