化石记录表明，在地球有动物居住的所有时期，已经有五次大灭绝发生，恐龙是最近的一次。
The fossil record indicates that in all the time that animals have inhabited Earth, there have been five great mass extinctions, dinosaurs being the most recent.
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.
因此，化石是识别地球历史上特定时期的标志。
Fossils are thus identifying markers for particular periods in Earth's history.
为了建立这样一个年表，有必要确定地球过去不同时期存在的陆冰的相对数量。
To establish such a chronology, it is necessary to determine the relative amounts of land ice that existed at various times in the Earth's past.
即使在没有冰川的时期，天文周期也会对地球的气候产生影响。
Astronomical cycles have an effect on Earth's climate even during periods when there is no glaciation.
一旦人们了解了这些板块是如何运动的，就有可能确定过去地球上大陆的运动，以及这些缓慢的运动如何在不同时期重塑了地球的特征。
Once it was understood how these plates move, it was possible to determine past movements of Earth's continents and how these slow movements have reshaped Earth's features at different times.
但是，告诉外星文明我们正处在地球的哪一时期并不是这个406公斤的金属球体的主要任务。
But telling alien civilizations when we lived and how Earth was in our time is not the main objective of this 406kg metal sphere.
地球的历史是包含了许多不如全新世稳定温和的时期的。
The planet’s history contains many less stable and clement eras than the Holocene.
最简单的方式莫过于你可以将不同时期的同一地球的快照放在一起来观察他们到底移开了多少距离。
In its simplest form, you are taking two snapshots of the same place, separated by a period of time, to see how far they have moved apart.
月亮被认为是由一个火星大小的星球一头撞进婴儿时期的地球所产生的。
The moon is thought to have formed when a Mars-sized body slammed into the infant Earth.
主流的理论假设认为，月球是大爆炸时期一火星大小的物体猛烈撞击地球而形成的。
The prevailing hypothesis is that the moon was formed from a giant impact event, when a Mars-sized object slammed into Earth.
地球之友组织的推行人罗宾·韦伯斯特说：“现在或许是欧洲最好的时期之一。”
Robin Webster, climate campaigner for Friends of the Earth, said: "This could have been one of Europe's finest moments."
已知到了那个时期，地球就不再变暖了，而北半球开始形成冰山。
By that time warm climate conditions ended and the ice caps in the northern hemisphere developed.
地球的历史可分为四个时期——依次经历冥古代、太古代、元古代和显生宙。
The history of Earth is divided into four eons —starting with the earliest, these are the Hadean, Archean, Proterozoic, and Phanerozoic.
地球的历史可分为四个时期——依次经历冥古代、太古代、元古代和显生宙。
The history of Earth is divided into four eons - starting with the earliest, these are the Hadean, Archean, Proterozoic, and Phanerozoic.
比如，在“雪球地球”时期火山爆发使得空气中增加了硫粒子，它阻挡了太阳光线，使地球冷却。
For instance, eruptions during the snowball-Earth period are thought to have added sulfur particles to the atmosphere, blocking sunlight and cooling the planet.
格温先生重点着笔于卡曼契人，他将全盛时期的卡曼契族形容为“地球最伟大的轻骑兵”。
Mr Gwynne’s focus is the Comanches, a tribe that he describes as “the greatest light cavalry on earth” during their heyday.
人类开始设法旅行或者居住到那些地球上极端环境的情况可以追溯到很早的时期。
Humans have a long history of making incredible journeys and carving out a living in even the most inhospitable and unforgiving environments Earth has to offer.
亲爱的人们，在2011年6月将开始一段30天的时期，在此之中将提供重要的更替完成，以及地球和人类的变化。
Dear Humans in June of 2011 will begin a 30-day period that will offer important shift completions and change to the Earth and indeed mankind.
上龙属于一种蛇颈龙，蛇颈龙是一亿五千万年前统治海洋的一种大型水栖爬行动物，其存在时期约与恐龙游荡地球同期。
Pliosaurs were a form of plesiosaur, a group of giant aquatic reptiles that terrorised the ocean 150m years ago, around the same time that dinosaurs roamed the Earth.
这些钻石很可能在两万年前，整个地球各地都被大片大片的冰川所覆盖着的时期，从钻石产生的地方顺着冰川流到印度来的。
These diamonds were probably carried from where they were formed to India by great sheets of moving ice that covered parts of the earth 20, 000 years ago.
吉尔研究了13000年前地球气温急速下降的一段时期。
She’s been researching a period of rapid cooling that occurred about 13, 000 years ago.
另外，二百年之后较短时期的火山活动再一次使得地球变热，海水变酸，从而再一次打击了生物，但是同样恢复的很快。
Another, smaller episode of volcanism 2m years later, which once again heated the planet and turned the seas acid, hammered life again-and again it recovered quickly.
网站上提供协会内部通讯的电子版—那份不怎么光彩的《平坦地球简讯》，都是上世纪七八十年代鼎盛时期刊发的。
The website features scanned issues of the society's newsletter, the notorious Flat Earth News, from its 1970s and 80s heyday.
在地球资源探测卫星的提名中这样写道：“在同时期里(1972- 1992)，如些规模的地球图片记录是独一无二的。”
As stated in the Landsat nomination: "There is simply no other image record of the Earth's land regions at this scale or over the same period of time (1972-1992)."
在那段时期的中间，也就是三叠纪时期，一颗小行星撞击了地球。
About halfway through that period, known as the Triassic, an asteroid struck Earth.
第二幅地图显示了没有时间显示的地球形成时期。
The second map shows Earth at the time of launch. That's time zero.
包括加州漂移到太平洋”在遥远的未来，如果任何一个外星文明到达地球，他们就会被告知地球形成的历史并且知道我们生活在哪个时期。
In the future, if any alien civilization arrives to Earth, they would be able to instantly tell the history of Earth's geography and know where in time we lived.
在全世界各地不同时期都有ufo目击的报告，引起人们关于外星生命以及地外生命是否访问过地球的争论。
UFO sightings have been reported throughout recorded history and in various parts of the world, raising questions about life on other planets and whether extraterrestrials have visited Earth.
在全世界各地不同时期都有ufo目击的报告，引起人们关于外星生命以及地外生命是否访问过地球的争论。
UFO sightings have been reported throughout recorded history and in various parts of the world, raising questions about life on other planets and whether extraterrestrials have visited Earth.
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