整个地球分为二十四时区,每个时区都有自己的本地时间。在国际无线电通信场合,为了统一起见,使用一个统一的时间,称为通用协调时(UTC, Universal Time Coordinated)。UTC与格林尼治平均时(GMT, Greenwich Mean Time)一样,都与英国伦敦的本地时相同。在本文中,UTC与GMT含义完全相同。
整个地球分为二十四时区,每个时区都有自己的本地时间。在国际无线电通信场合,为了统一起见,使用一个统一的时间,称为通用协调时(UTC, Universal Time Coordinated)。UTC与格林尼治平均时(GMT, Greenwich Mean Time)一样,都与英国伦敦的本地时相同。在本文中,UTC与GMT含义完全相同。
据说死亡人数已经上升到7000.作者: 未注册用户 时间: 2008-5-12 10:36
这次好在在白天,也好在不是在大城市,没有太多高层建筑。作者: li331 时间: 2008-5-12 10:46
天将降大任于斯国也,必先撞其火车,抢其火炬,震其国土,涨其物价,跌其股票,空泛其民
今天是距离北京2008年8月8日还有88天,所以举国同震,以示庆祝
上联:神州共震迎奥运
下联:华夏抖擞反藏独
横批:震撼2008作者: Sedona 时间: 2008-5-12 10:54 标题: Theory of Plate Tectonics Earth, either lithosphere or asthenosphere, is not absolute solid or rigid, in a relative sense. Assuming the water density is 1, lithosphere has a density like 3.7 (can't remember exactly by me, knowledge of 20+ years old), while asthenosphere, mainly magma, has that from 1.4 to 2.7.
Lighter Magma will flow upward while heavier earth crust will sink. Such a flow will shift the earth plate, causing plates to clash and building pressure along the edges or faultlines of the lithosphere..
Pressure once hitting the threshold will release, causing vibration of the plates, which is earthquake.
In China, most dangerous earthquake areas include:
1. Taiwan. Pacific plate moving into Asian plate.
2. Beijing-Tinjian-Tangshan due to the interaction of the smaller Northeast Asian plate and the Pacific plate.
3. SZ, Yunan, Szechuan and the extension all the way to Shanxi due to the mountain building of the Himalayas.
Plate Tectonics, theory that the outer shell of the earth is made up of thin, rigid plates that move relative to each other. The theory of plate tectonics was formulated during the early 1960s, and it revolutionized the field of geology. Scientists have successfully used it to explain many geological events, such as earthquakes and volcanic eruptions as well as mountain building and the formation of the oceans and continents.
Plate tectonics arose from an earlier theory proposed by German scientist Alfred Wegener in 1912. Looking at the shapes of the continents, Wegener found that they fit together like a jigsaw puzzle. Using this observation, along with geological evidence he found on different continents, he developed the theory of continental drift, which states that today’s continents were once joined together into one large landmass.
Geologists of the 1950s and 1960s found evidence supporting the idea of tectonic plates and their movement. They applied Wegener’s theory to various aspects of the changing earth and used this evidence to confirm continental drift. By 1968 scientists integrated most geologic activities into a theory called the New Global Tectonics, or more commonly, Plate Tectonics.
II Tectonic Plates
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Tectonic plates are made of either oceanic or continental crust and the very top part of the mantle, a layer of rock inside the earth. This crust and upper mantle form what is called the lithosphere. Under the lithosphere lies a fluid rock layer called the asthenosphere. The rocks in the asthenosphere move in a fluid manner because of the high temperatures and pressures found there. Tectonic plates are able to float upon the fluid asthenosphere because they are made of rigid lithosphere.作者: gongyu 时间: 2008-5-12 10:56 最初由[li331]发布
天将降大任于斯国也,必先撞其火车,抢其火炬,震其国土,涨其物价,跌其股票,空泛其民
今天是距离北京2008年8月8日还有88天,所以举国同震,以示庆祝
上联:神州共震迎奥运
下联:华夏抖擞反藏独
横批:震撼2008