The size of the oceans dominates the view of earth from space.
插叙的作用>pollSeawater is pure water plus dissolved solids and gas.The dissolved solids come from weathering process of the continental rocks being dissolved by rain and flowing out to a with the rivers. The gas come from the atmosphere. As water is a universal solvent, many different compounds are dissolved in it. A 1-kg sample of saltwater contains 35g of dissolved compounds, including inorganic salts, organic compounds from living organisms. The solid substances are known as “salts” and their total amount in the water is referred to by a term known as salinity (expresd as parts per thousand ).Oceanic salinity generally has a range from 34 to 37 parts per thousand. Variations from place to place are due to factors such as rainfall, evaporation,biological activity and radioactive decay. Salinitues are higher in the tropics due to high evaporation rates. Fresh supplies of salts are now being added to the oceans from the rivers at roughly the same rate of that they are being removed by various physical, chemical and biological process.
The vast quantity of water aro from the Earth’s interior as it cooled. The origin of the ocea
成员英文
ns back to the time of the earth’s formation about 4.6 billion years ago, when our planet was forming through the accumulation of smaller objects, called planetesimals. There are basically three possible sources for the water. It could have parated out from the rocks that make up the bulk of earth; or arrived as part of a late-accreting veneer of water-rich meteorites, similar to the carbonaceous chondrites that we e today; or arrived as part of a late-accreting veneer of icy planetesimals, that is, comets.
The composition of the ocean offers some clues as to its origin. If all the comets contain the same kind of water ice that we have examined in Comets Halley and Hyakutake-the only ones who water molecules we’ve been able to study in detail-then comets cannot have delivered all the water into the earth’s oceans.We know this becau the ice in the comets contains twice as many atoms of deuterium (a heavy isotope of hydrogen) to each atom of ordinary hydrogen as we find in awater.
译文：影评英文
从太空中看，地球表面几乎都是被海洋覆盖的。
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海水是由纯水及溶解在其中的固体和气体组成的。这些固体来自于陆壳岩石的风化作用，它们溶解在雨水中随着河水涌入大海。而这些气体均来自大气层。因为水有着很强的溶解力，很多不同的成分都能溶于海水中。1千克海水样本中就含有35克溶解物，包括无机盐以及来自生物体的有机化合物。这些固体物质被称作“盐”，盐的含量用含盐量来表示（即用千分之几来表示）。海水的含盐量通常在千分之三十四到千分之三十七之间。之所以是一个变量，是由于诸如降雨量，海水蒸发量，生物活性以及放射衰变等多种因素造成的。热带地区由于蒸发量较大进而海水中的含盐量较高。河水为海洋提供新盐，与此同时，海水中与之几乎等量的盐分通过一系列的物理、化学、生物作用被带走。
ccd是什么>powergrip海洋中的巨量海水源自于地球内部，经过逐渐冷却而形成。海洋的起源在时间上可以追溯到地球形成之初，大约是46亿年前，那时的地球是由许多微小颗粒积聚而成的，被称为微行星。水有三种可能的来源：主要由泥土形成的岩石可能会分离出水来；或者是来自一种后期聚集增生的富水陨星块体，与今天看到的碳质陨石相似；又或者是来自于后期增生的冰质小行星体——彗星。
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海洋的组成成分为海洋的形成提供了一些线索。如果所有的彗星都含有与我们在哈利彗星
及百武二号彗星上检测到的同质的冰水，（所有彗星中我们仅能细致研究哈利彗星及百武二号彗星上的水分子。）那么彗星不可能将所有的水输送到地球上。因为我们知道彗星上冰中含的氘原子(氢的一种重同位素：重氢)是氢原子(现代海水中常见的氢原子)相对原子质量的两倍。
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