地球的时变主惯性矩和变化的自转(英文)   总被引：1，自引：0，他引：1  

SHEN Wenbin CHEN Wei SUN RongSHEN Wenbin  School of Geodesy  Geomatics  Wuhan University  Luoyu Road  Wuhan  China  The Key Laboratory of Geospace Environment  Geodesy  Wuhan University  Luoyu Road  Wuhan  China. 《地球空间信息科学学报》2008,(2)

Based on the gravity field models EGM96 and EIGEN-GL04C, the Earth's time-dependent principal moments of inertia A, B, C are obtained, and the variable rotation of the Earth is determined. Numerical results show that A, B, and C have increasing tendencies; the tilt of the rotation axis increases 2.1×10-8 mas/yr; the third component of the rotational angular velocity, ω 3, has a decrease of 1.0×10-22 rad/s2, which is around 23% of the present observed value. Studies show in detail that both θ and ω 3 experience complex fluctua-tions at various time scales due to the variations of A, B and C.  相似文献   

Evolution of the composition of seawater through geologic time, and its influence on the evolution of life   总被引：2，自引：2，他引：0  

Tsuyoshi Komiya  Takafumi Hirata  Kouki Kitajima  Shinji Yamamoto  Takazo Shibuya  Yusuke Sawaki  Tomoko Ishikawa  Degan Shu  Yong Li  Jian Han 《Gondwana Research》2008,14(1-2):159

The redox state of the surface environment of the early Earth is still controversial, and a detailed and quantitative estimate is still lacking. We carried out in-situ analyses of major, trace, and rare-earth elements of carbonate minerals in rocks with primary sedimentary structures in shallow and deep sea-deposits, in order to eliminate secondary carbonate and contamination of detrital materials, and to estimate the redox condition of seawater through time. Based on the Ce content and anomalies of the carbonate minerals at given parameters of atmospheric CO₂ content (pCO₂) and Ca content of seawater, we calculated the oxygen contents of shallow and deep seawater, respectively. The results show that the oxygen content of the deep sea was low and constant until at least 1.9 Ga. The oxygen content of shallow seawater increased after 2.7 Ga, but fluctuated. It became quite high at 2.5 and 2.3 Ga, but eventually increased after the Phanerozoic. In addition, the calculation of a high pCO₂ condition shows that seawater was more oxic even in the Archean than at present, suggesting a relatively low pCO₂ through geologic time.Our detailed calculations from compositions of carbonate minerals in Three Gorge area, south China show a low oxygen content of seawater after the Snowball Earth until the late Ediacaran, an increase in the late Ediacaran, and a significant decrease around the Precambrian–Cambrian and Nemakit/Daldynian–Tommotian boundaries. These variations were possibly caused by global regression and dissolution of methane hydrates.  相似文献   

Models on Snowball Earth and Cambrian explosion: A synopsis   总被引：5，自引：5，他引：0  

S. Maruyama  M. Santosh 《Gondwana Research》2008,14(1-2):22

During the late Proterozoic from 1000 to 542 Ma, the Earth is thought to have been frozen at least during two times: in the Sturtian (715–680 Ma) and in the Marinoan (680–635 Ma) global glaciations. Following the Marinoan Snowball Earth, large multi-cellular animals of the Ediacara fauna flourished as a prelude to the Phanerozoic world. Here we summarize the most popular models on the cause and cessation of Snowball Earth. Episodic decrease of greenhouse gas occurs through the effect of erosion and weathering promoted by either mountain building or by an increase in the coastlines during the break-up of supercontinents. Effects on the globe caused by true polar wander, eruption of voluminous flood basalts, or dramatic reduction in planetary obliquity can also lead to ice ages and mass extinction. A radically revised concept based on Earth's magnetic intensity has also been proposed, which explains the true polar wander through a quasi-polar dynamo model. The ‘switch-on’ and ‘switch-off’ of the Earth's strong dynamo can lead to the onset and disappearance of the Snowball Earth. The galactic model infers that gamma ray burst associated with starburst creates huge amounts of clouds which would cut off sun rays and freeze the Earth.The Snowball Earth event is considered to have exerted a significant control on the subsequent revolutionary changes in the evolution of life forms. Although according to the biological clock, extensive re-organisation of genome is thought to have been completed by around 900 Ma, the evolution of modern life in Cambrian occurred only after the geochemical bridge was in place with elevated oxygen and nutrient levels in lakes that developed within continental rifts where the hydrothermal system in the granitic basement created the chemical environment enriched in Ca²⁺, Fe²⁺, V, Mo, HCO₃, phosphate and other elements required for building the skeleton and bone of the first modern animals. With cosmic radiation exerting a significant control on the mutation, the Neoproterozoic Earth history illustrates the possible link from Galaxy to the genome level.  相似文献   

Metamorphic decarbonation in the Neoproterozoic and its environmental implication   总被引：2，自引：1，他引：1  

S. Omori  M. Santosh 《Gondwana Research》2008,14(1-2):97

Metamorphic decarbonation reactions and volcanic degassing lead to significant influx of CO₂, a major greenhouse gas, into the ocean-atmosphere system from the solid Earth. Here we present quantitative estimates on CO₂ derived through metamorphic degassing during ultrahigh-temperature (UHT) metamorphism in the Neoproterozoic through the mineralogical and geological analyses of the UHT decarbonation. Our computations show that an extra flux of CO₂ was added to the atmosphere through a Himalayan scale UHT metamorphism to the extent of 6 × 10¹⁶ to 3.0 × 10¹⁸ mol/my, for a duration of 10 my. A calculation of the impact of the extra CO₂ influx to the global mean temperature in the context of carbon cycle and greenhouse effect of CO₂ shows that at the peak influx stage, the steady state temperature would be raised by 4 °C from 15 °C and by 13 °C from 4 °C. Our results have important bearing in evaluating the mechanism of melting and the duration of the Snowball Earth. Our estimate of the maximum degassing rate during UHT metamorphism suggests that the duration of the Marinoan snowball Earth was probably shorter, and the recovery from an ice-covered Earth to ocean-covered Earth was faster than previous estimates.  相似文献   

基于浏览器的Google Earth交互式系统开发技术     

张慧 《山东地质》2008,(12):30-32

介绍了基于浏览器的Google Earth交互式系统、开发技术、Struts框架和Ajax技术,描述了系统架构及开发途径。基于浏览器的Google Earth交互式系统具有广泛的商业应用前景。  相似文献   

Virtual Earth API在Web地图服务中的应用   总被引：1，自引：0，他引：1  

龙岳红  邹峥嵘  王科 《测绘科学》2008,33(6):199-201,228

自2005年地图搜索服务兴起以及Google公司在线地图Google Map的发布,web地图服务成为新一轮竞争热点,微软、雅虎及亚马逊等公司纷纷参与竞争。本文介绍了微软Virtual Earth API最为重要的几个功能及其实现方法,演示了使用Virtual Earth技术建立Web地图服务的方法,为学习微软Virtual Earth制图技术和使用Virtual Earth地图控件提供借鉴。  相似文献   

郑州市空间信息基础设施建设与应用研究     

朱刘娟  魏峰远 《测绘与空间地理信息》2008,31(2):10-13

数字地球是21世纪的重大技术工程,数字城市是数字地球应用的主要方面之一。依据我国数字城市建设的现状,提出构建"郑州市空间信息基础设施",并对其内容、应用、关键技术、实现策略等进行了论述及探讨。  相似文献   

Teaching Topographic Map Skills and Geomorphology Concepts with Google Earth in a One-Computer Classroom     

Hsiao-Ping Hsu  Bor-Wen Tsai  Che-Ming Chen 《The Journal of geography》2018,117(1):29-39

Teaching high-school geomorphological concepts and topographic map reading entails many challenges. This research reports the applicability and effectiveness of Google Earth in teaching topographic map skills and geomorphological concepts, by a single teacher, in a one-computer classroom. Compared to learning via a conventional instructional method, students learning with Google Earth do not have different geomorphological concepts development because both settings enable students to learn with similar static representation. However, students learning with Google Earth improve topographic map skills significantly compared to the conventional instructional method. This is because of the 3D landscape visualization and prior knowledge connections available with Google Earth.  相似文献   

科学数据共享实践：以国家地球系统科学数据中心为例   总被引：2，自引：0，他引：2  

杨雅萍  姜侯  孙九林 《地球信息科学学报》2020,22(6):1358-1369

地球系统科学是一门综合性交叉学科,起源于全球变化研究,受益于遥感技术进步,现已进入大数据时代,人工智能技术成为解决地球系统科学前沿问题的新手段。科学数据共享是推动科学发展、提升数据价值的关键,经过长期的探索和实践,全球已形成完善的数据资源管理政策与机制、持续的数据共享服务体系、多元化的科学数据整合模式,并且新的理念不断推动数据共享创新发展,其中“可发现、可访问、可互操作和可重用”原则和数据出版备受推崇。我国颁布了国家层面的政策法规,着重推动国家级科学数据中心建设、科技项目数据资源汇交及数据出版。借鉴国外数据共享经验,结合国内实际发展情况,我国探索出具有中国特色的地球系统科学数据资源分类体系,在元数据、分布式互操作、大数据分析和共享服务等关键技术方面都取得了重大突破。本文以国家地球系统科学数据中心为例,系统梳理了国内地球系统科学领域的数据共享实践进展,详细介绍了国家在地球系统科学领域的数据共享实践及其成效。国家地球系统科学数据共享工作已探索形成成熟稳定的运行服务机制、研制出适用于多源分散地球系统科学数据的标准体系、 建成多学科多时空尺度的地球系统科学数据库群、自主研发海量异构数据共享网络技术体系与服务系统,促进了地球系统科学的科学发展,同时也推动了数据共享理念的传播与推广。然而,数据孤岛现象、共享服务系统标准化程度低、系统技术标准未对接国际规范等问题仍然较为突出,阻碍了地球系统科学数据开放与共享。未来,随着共享个性化需求被激活,定制化的“数据+知识”服务有望成为主流趋势,将给数据共享带来新的机遇和挑战。  相似文献   

台站插值技术对检测固体地球变化的影响分析     

赫剑波  孙建军 《测绘与空间地理信息》2016,(10):43-45

搜集了全球约4 000个GNSS测站实测数据(站坐标和速度场信息),对固体地球体积及其变化率进行计算分析。采用板块运动模型插值方法对台站进行插值,使全球测站分布更加均匀。利用Delaunay数学模型计算固体地球体积及其变化率的结果发现:基于板块运动模型进行台站插值可以有效地提高计算结果的误差精度,不会对地球最终形态变化结论产生影响,台站数量及其分布均匀程度对计算最终结果影响较大。  相似文献