落跑蚂蚁
The Earth's surface is very young. In the relatively short (by astronomical standards) period of 500,000,000 years or so erosion and tectonic processes destroy and recreate most of the Earth's surface and thereby eliminate almost all traces of earlier geologic surface history (such as impact craters). Thus the very early history of the Earth has mostly been erased. The Earth is 4.5 to 4.6 billion years old, but the oldest known rocks are about 4 billion years old and rocks older than 3 billion years are rare. The oldest fossils of living organisms are less than 3.9 billion years old. There is no record of the critical period when life was first getting started71 Percent of the Earth's surface is covered with water. Earth is the only planet on which water can exist in liquid form on the surface (though there may be liquid ethane or methane on Titan's surface and liquid water beneath the surface of Europa). Liquid water is, of course, essential for life as we know it. The heat capacity of the oceans is also very important in keeping the Earth's temperature relatively stable. Liquid water is also responsible for most of the erosion and weathering of the Earth's continents, a process unique in the solar system today (though it may have occurred on Mars in the past).
昏昏头了
earth id the third planet in distance outward from the Sun.Believed to be about 4.6 billion years old, it is some 92,960,000 mi (149,600,000 km) from the Sun. It orbits the Sun at a speed of 18.5 mi (29.8 km) per second, making one complete revolution in 365.25 days. As it revolves, it spins on its axis, rotating once every 23 hours 56 minutes 4 seconds. The fifth largest planet of the solar system, it has an equatorial circumference of 24,902 mi (40,076 km). Its total surface area is roughly 197,000,000 sq mi (509,600,000 sq km), of which about 29% is land. Earth's atmosphere consists of a mixture of gases, chiefly nitrogen and oxygen. Its only natural satellite, the Moon, orbits the planet at a distance of about 238,860 mi (384,400 km). Earth's surface is traditionally subdivided into seven continental masses: Africa, Antarctica, Asia, Australia, Europe, North America, and South America. These continents are surrounded by the so-called World Ocean, which is broken down into three major bodies: the Atlantic, Pacific, and Indian oceans. Broadly speaking, Earth's interior consists of two regions: a core composed largely of molten, iron-rich metallic alloy; and a rocky shell of silicate minerals comprising both the mantle and crust (See also Moho; lithosphere). Fluid motions in the electrically conductive outer core generate a magnetic field around Earth that is responsible for the Van Allen radiation belts. According to the theory of plate tectonics, the crust and upper mantle are divided into a number of large and small plates that float on and travel independently of the lower mantle. Plate motions are responsible for continental drift and seafloor spreading and for most volcanic and seismic activity on Earth.
大眼睛鱼儿
What is the most useful stuff(这个词美语里面用,可以代替一切物品,如果你不喜欢可以用thing)?Absolutely,it's computer.But,do you guys konw what is the most useful program?Ladies and gentleman,the incredible stuff - Google Earth.I'm sure that a great many people know what the"google"thing is,.Yeah,just as you know,Google is a company which owns the biggest search engine all over the world.And it has made a few many great program as well.For instance,Google talk,which works as QQ and MSN does.And also the Google Desktop,Google group and so on.So anyway,Google Earth is so amazing that you can hardly imagine without a run by yourselves.Today,however,I am going to show you how it works.Foremost,you can see a earth here,which is simulated.Secondly,you can double-click where you wanna(want to的缩写.不会读就用want to吧)visit.And your view will zoom in.Plus,(这里是个主语从句,句首省略了that,不是错句)how clear your view is does not depend on your computer,but depends on the NASA.Yes,the one and only NASA ,in chinese it's (美国)国家航空和宇宙航行局.Of course,some European country have done GE(Google earth) a favor,too. Pictures are received from servers.And servers's pics are received from satellites.The more important this place is.the clearer whose pics are.What's more,the GE is totally free!(结尾我不知道要不要,顺便帮你写了.) That's all Thank you for your attention,.
优质英语培训问答知识库
