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921.
922.
矿物和结构分析揭示了南极洲乔治王岛柯林斯冰帽一支 80 .2 m冰芯中的 9层深褐色沉积物的火山灰特征。本文从冰川处于稳定状态的假定出发 ,根据 Dansgaard- Johnsen流动模式断代结果 ,建立了南设得兰群岛火山喷发序列。依冰芯记录判断 ,该区 1 650年以来的 340年间 ,共有 7轮火山喷发。1 875~ 1 92 5年间似为火山活跃期 ,喷发地点可能主要在欺骗岛 ;1 650~ 1 80 0年间为一相对平静期 ;此后一个世纪不太稳定 ;而过去的 1 0 0年间基本平静 ,只是世纪初和 50~ 70年代间各有一段动荡期。冰芯中记载的大多数火山喷发可在该区有关文献中找到记录。没有记录在案的几例喷发事件需进一步调查。冰芯中缺失 1 967~ 1 970年欺骗岛火山灰层位表明 ,研究得到的火山序列仍未包含所有的喷发事件。但本文展示的该区过去 340年间火山活动基本趋势并不因此而改变。 相似文献
923.
The geomorphology of Heard Island-McDonald Island is primarily the product of close interplay between volcanism, glaciation, and vigorous marine processes in a stormy sub-Antarctic environment. The dominant landform is the strato-volcano Big Ben (2745m), which is the highest mountain on Australian territory outside Antarctica. Other volcanic landforms include scoria cones, domes, open vertical volcanic conduits, lava flows and lava tubes. Volcanic activity is ongoing from the summit of Big Ben, and from Samarang Hill on McDonald Island. Early, but unproven, glacial sediments may exist within the Late Miocene - Early Pliocene Drygalski Formation, which forms a 300m high plateau along the northern coast of Heard Island. Growth of the present glaciers, some of which reach sea level, has been a response to progressive growth of the volcanoes. A variety of erosional and depositional glacial landforms is present, including major lateral moraines and extensive hummocky moraines. Vigorous longshore drift and an abundant sediment supply have produced a large spit at the downdrift end of the island, and formed bars from reworked glacigenic sediment that now impound proglacial estuarine lagoons, some of which have grown rapidly over recent decades as tidewater glaciers have retreated. Integrated study of the volcanic, glacial and coastal sequences offers the possibility of constructing a well-dated record of climate change. Research into the geomorphology, surficial sediments, and contemporary geomorphological processes, including glaciofluvial sediment flux, is also important as an aid to environmental management on land, and to management of the adjacent marine environment. 相似文献
924.
Array analysis using circular-wave-front geometry:an application to locate the nearby seismo-volcanic source 总被引:4,自引:0,他引:4
Javier Almendros Jesús M. Ibáñez Gerardo Alguacil & Edoardo Del Pezzo 《Geophysical Journal International》1999,136(1):159-170
The zero-lag cross-correlation technique, used for array analysis in the hypothesis of plane waves, has been modified to allow the wave front to be circular. Synthetic tests have been performed to check the capability of the method, which returns the input test data when the source–array distances are not greater than two or three times the array aperture. For this distance range the method furnishes an estimate of the apparent velocity and the epicentral coordinates of the source. For more distant sources the method becomes equivalent to that based on the planar-wave approximation, which gives an estimate of the backazimuth to the source and the apparent velocity. The method has been applied to seismic data recorded at the active volcano located at Deception Island, Antarctica. 35 volcanic long-period events occurring in a small swarm were selected. Results show that the epicentres are close to the array (between 0.4 and 2 km) and aligned in a SW direction, in agreement with one of the main directions of the fracture system of Deception volcano. 相似文献
925.
对海南岛秋季非热带气旋暴雨特性的分析发现: 暴雨的发生、维持和消失主要与大陆冷高、南海低值系统、热带云团活动密切相关,暴雨一般与华南沿海的低空偏东风急流相伴。T106 流场预报为低空急流的生消预报提供了一个客观依据, 文章还对T106 多个物理量场作了误差分析 相似文献
926.
927.
田横岛旅游业近年来获得迅速的发展,已从一个荒岛渔村变成了山东沿海旅游景点。为了充分挖掘该岛旅游资源,使旅游业得到了可持续发展,必须根据该岛的自然环境 及旅游业产业化的经济活动规律,进一步发展田横岛旅游业。本文将从以上两方面论述田横岛旅游业的未来及其产业化的途径。 相似文献
928.
The genetic structure of a population of the Japanese turban shell, Turbo (Batillus) cornutus at Sata-Misaki Point, on the southern coast of Kyushu Island, was determined on the basis of nucleotide sequences of mitochondrial DNA and compared with that of a population of the western coast of Kyushu Island. The significant genetic differentiation between these two populations suggests that the courses of the warm currents along the coast of the Kyushu Island have been relatively stable after the divergence between the two genetically distant groups of the Japanese turban shell, which was estimated to have occurred during some period in Pleistocene. 相似文献
929.
福建平潭岛旅游地质资源特征浅析 总被引:3,自引:1,他引:2
福建平潭岛又名海坛岛 ,是祖国大陆距台湾最近点 ,不但有着秀丽无比的海域风光 ,别具一格的海岛民俗 ,最具特色的还是它的地质地貌景观 ,专家们称之为“天然的地学博物馆”,具备广阔的旅游地学资源开发前景。 相似文献
930.
Preferred characteristics of biological indicators for heavy metal monitoring in marine ecosystems were documented 30 years ago. Heavy metal data from Raine Island on the outer-northern Great Barrier Reef are presented to introduce additional attributes for consideration, including a widened choice of biological tissues due to advances in trace heavy metal analysis. Kidney tissues, visceral mass and adductor muscle from the giant clam (Tridacna maxima), muscle tissue from trochus (Trochus niloticus) and axial muscle from four species of fish were targeted. The kidneys of giant clams had concentrations of heavy metals from 2 (Zn) to 2780 (Ni) times higher than corresponding concentrations in adductor muscles. Also, tissues of giant clam and the muscle of trochus gave different signals with respect to bio-available heavy metals. Linear correlations for heavy metals within and between tissues of giant clam and within muscle tissue of trochus, offer opportunities for the use of surrogates as well as a possible mathematical basis for assessing trends in heavy metal pollution. 相似文献