把它们从地球的表面上彻底清除。
从这些研究中，科学家们得出结论，海洋覆盖着原始地球的表面，其中含有构成生命的基本分子。
From these studies, scientists have concluded that the surface of the primitive Earth was covered with oceans containing the molecules fundamental to life.
地球的表面被水覆盖，其中有97.5%是海水。
While the earth's surface is covered by water, 97.5 percent of it is salt water.
这是因为地球的表面是圆的而不是平的。
This is because the surface of the earth is not flat but round.
在地球的表面，地震会使地面发生震动，有时则会发生地面移动。
At the earth's surface, earthquakes manifest themselves by shaking and sometimes displacing the ground.
当它们穿行到地球的表面时，地表成了带正电的带电体。
When they travel to the surface of the Earth, the surface becomes positively charged.
滚烫的岩浆，或者叫熔岩，经过了冷却以后就形成了地球的表面。
The hot magma, or lava as it is called, cols and builds up on the surface of the earth.
随着气候的变化以及土壤沙漠化，人类从根本上改变了地球的表面。
With climate change, concrete deserts and agriculture, human beings have fundamentally altered the face of the Earth.
其根本原因，不外乎是地球的表面受了两种力，一是外力，二是内力。
The fundamental reason, nothing more than the earth's surface is subject to two forces, one is the external force, the two is the internal force.
但是现在科学家们搞明白了，地球的表面不是像我们以为得那样一成不变。
Scientists now know, however, that the surface of the Earth is not as permanent as had been thought.
但是河流在地球的表面雕刻自己的路径已有数百年的历史，它们将继续下去。
But rivers have carved their way over the earth's face for centuries and they will stay.
地球表面低重力直接导致了火星上火山的巨大高度。
The great height of Martian volcanoes is a direct consequence of the planet's low surface gravity.
很明显，除了利益和民族主义，其他紧急的事物将迫使人类在地球表面留下他们的足迹。
It is clear that imperatives other than profits or nationalism will have to compel human beings to leave their tracks on the planet's reddish surface.
地球表面最有趣的特征之一就是盾状火山。
One of the most interesting features on the surface is, in fact, the shield volcanoes.
据估计，地球表面另外四分之一的土地正面临沙漠化威胁。
It has been estimated that an additional one-fourth of the Earth's land surface is threatened by this process.
臭氧在距地球表面12至30英里的地方形成一个保护层。
Ozone forms a protective layer between 12 and 30 miles above the Earth's surface.
它们阻挡了大部分的太阳能，使它永远无法到达地球表面。
They block most of the solar energy so it never reaches Earth's surface.
所以沉积物被运输，然后沉积，随着时间的推移，它在地球表面形成了层。
So sediment is transported and then deposited and it forms layers on the Earth's surface over time.
更多的红外辐射将被吸收并重新辐射回地球表面。
More infrared radiation would be absorbed and reradiated back to the Earth's surface.
这表明，地球上的水可能来自内部，由于地质活动，被带到表面形成海洋。
This suggests that Earth's water may have come from inside, driven to the surface to form the oceans, by geological activity.
即使地球表面并没有被这种轰炸所灭绝，但除了最原始的生命形式之外，几乎不可能有其他生命形式幸存下来。
Even if Earth's surface were not actually sterilized by this bombardment, it is unlikely that any but the most primitive life-forms could have survived.
它的表面大部分是在过去十亿年里形成的，使得它比地球以外的任何岩石行星都更新鲜活跃。
The surface formed mostly in the last billion years, which makes it fresher and more recently active than any rocky planet other than earth.
构成地球表面的那些构造板块极其缓慢但剧烈的运动，也可能导致异地物种形成。
Allopatric speciation can also be brought by the imperceptibly slow but colossal movements of the tectonic plates that make up Earth's surface.
复杂的生命在地球表面进化，而不是在火星或太阳系的其他行星上，因为在那些行星上，早期的地表生命被紫外线杀死了。
Complex life evolved on the Earth's surface, but not on Mars or other planets in the solar system because on those planets, early surface life was killed by UV radiation.
另一方面，像地球的卫星这种相对温暖、表面引力较小的天体，它们连最重的气体也无法容纳，因此也没有大气层。
On the other hand, a comparatively warm body with a small surface gravity, like Earth's moon, is unable to hold even the heaviest gas and thus lacks an atmosphere.
一些已经从地球表面消失了，其他的正在慢慢地死亡，但所有的都经历了变化，因为它们已经接触到一个不断扩张的机器文明。
Some have vanished from the face of the earth, others are dying slowly, but all have undergone changes as they have come into contact with an expanding machine civilization.
地球表面并不是由构成地壳的单块岩石构成，而是许多紧密相连的“构造板块”，像一块巨大的拼图。
Earth's surface is not made up of a single sheet of rock that forms a crust but rather a number of "tectonic plates" that fit closely, like the pieces of a giant jigsaw puzzle.
作为地质学家，我们研究地球表面的沉积层以估算过去地质时期的年代。
As geologists, we examine layers of sediment on the Earth' s surface to approximate the dates of past geologic time periods.
作为地质学家，我们研究地球表面的沉积层以估算过去地质时期的年代。
As geologists, we examine layers of sediment on the Earth' s surface to approximate the dates of past geologic time periods.
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