5.Changes in Water Levels
5.海平面变化说
There have been five mass extinctions in Earth's history. A professor of geology at the University of Wisconsin-Madison believes that there's one culprit responsible for all five — change in sea levels. Since Earth formed about 4.54 billion years ago, it's been constantly changing. As a result, land masses and oceans have evolved quite a bit. And any time a mass extinction happened, it's correlated with a change in sea levels. While ocean life would have been affected the most, creatures on land would have been devastated as well. In some areas there would have been massive flooding. On a global scale, ocean cycles would have changed radically and drastically affected the environments where land creatures would have lived, ate and drank.
在地球演变史上，有五次大规模的物种灭绝。威斯康辛麦迪逊大学的地质学教授认为，在这五次大灭绝中，罪魁祸首就是海平面的改变。从454万年前地球形成至今，海平面就一直在不断的变化，从而导致大陆和海洋产生了很大的演变。每一次大灭绝发生，都和海平面的改变有关。尽管在每一次的大灭绝中，海洋生物受到的影响都最大，但陆地上的物种也会受到大规模的毁灭。在某些地区，当海平面改变时，会发生很大的洪水。放眼全球，海平面的改变会从根本上改变海洋循环，并会极大地影响到那些在陆地上栖息的物种。

4.Disease
4.病毒侵入说

From looking at mosquitoes and ticks stuck in amber, Dr. George Poinar from Oregon State University said that germs started to emerge at the same time the dinosaurs were dying out, and it's possible the mighty dinosaurs were brought down by a microscopic plague.
通过研究蚊子和扁虱的琥珀标本，来自俄勒冈州立大学的乔治皮奥纳教授表明，细菌出现之时恐龙正处于濒临灭绝的时期，他认为很有可能是一场细菌瘟疫导致了这些庞大恐龙的消失。
Disease would have been devastating to dinosaurs, because they wouldn't have built up an immune system and they bred very slowly. Bugs would have simply transferred the disease to all the dinosaurs until they were wiped out, but mammals were able to survive simply because the diseases didn't affect them.
疾病的流行导致了恐龙的毁灭，其原因是恐龙不具有免疫系统且繁殖速度非常慢。寄生虫将病毒传播给恐龙，导致了它们的灭绝，然而同时期的哺乳动物却存活下来的原因就是它们不受疾病的影响。

3.Comet
3.彗星撞击说

A theory that stretches back to 1980 is that the death of the dinosaurs was caused by a different kind of impact event — one created by a comet. A comet is made up of ice, dust, rocky materials and organic compounds, while asteroids are usually made up of metal and rock. Comets are also smaller, and move a lot faster.
追溯到1980年，当时流行着一个关于恐龙灭绝的理论，即恐龙的灭绝是由于受到各种行星的撞击，其中影响最大的就是彗星的撞击。彗星主要是由松散的冰质、尘埃、小岩石和各种有机物组成，而行星则是由金属和岩石组成。此外，彗星的飞行速度更快，体积也更小。
Detractors say that a comet wouldn't have been big enough to cause the Chicxulub crater. However, researchers said that if the comet was moving fast enough, it could have caused a crater of that size. Not only that, but it would have sent more dust and debris into the air than an asteroid. The end result would have been the same either way, but it's still a question worth debating.
反对者认为，彗星并没有大到可以撞击地球继而造成希克苏鲁伯陨石坑。然而研究人员指出，只要彗星的飞行速度足够快，就可以撞击出同等大小的陨石坑。不仅如此，同小行星相比，彗星撞击会喷发更多的暗物质和残骸到大气层。虽然，不论哪种方式，最终结果都相同，但这仍然是一个值得探讨的问题。

2.Volcano
2.火山爆发说

The most metal theory on our list is that a volcanic region known as the Deccan Traps, located in what is now India, erupted. The eruption would have spewed out sulfur into the air for 10,000 years — 10 times the emissions put into the air by an asteroid. This would have caused incredible global warming and the acidification of the oceans.
位于印度的德干玄武岩地区的火山爆发是本列表中最能说服人的。伴随这次火山爆发而来的硫足以在大气中弥漫一万年，这相当于10次小行星撞击。因而产生了惊人的温室效应和海水酸化。
This decades old theory was given more credence in 2009, when oil companies drilling below the ocean surface off the east coast of India found eons old lava filled sediments. They analyzed the sediment and found fossils from the time of the K-Pg extinction.
2009年，这个数十年的旧理论被增添了更多佐证。在印度东海岸进行石油钻探时，有一家石油公司发现了亿万年之久的火山岩沉积物。经过分析，他们认为这些火山岩沉积物形成于白垩纪末期。

1.Combined Event
1.综合原因说

Many of the events listed here could have come together within a relatively short time span. While researchers debate what exactly was the culprit, they don't deny that these other cataclysmic events could have happened as well. For example, there's evidence of an asteroid or comet hitting the Earth and volcanic eruptions happening around the same time. Also, if an asteroid did hit the Earth, hypercanes and firestorms could have started. If there were survivors, disease and changes in sea level would have been devastating, and they might not have been able to compete against mammals. With so many things going wrong in such a short period of time, these small-brained creatures were simply overwhelmed by devastation.
以上列举的这一系列事件在同一时期内的共同作用很可能也是导致恐龙灭绝的原因。科学家们在讨论最可能导致恐龙灭绝的原因时，并没有否定其他可能同时发生的灾难性事件。比如，某一次的行星撞击和火山爆发就很可能是同时发生的。一旦地球与小行星发生碰撞，超级飓风和火焰风暴也会随之发生。即便经历过这一切的恐龙还能捡回一条命，但它们还是会被海平面的变化以及疾病所毁灭，亦或是败于同哺乳动物的生存竞争中。伴随着如此多的灾难，小脑袋的恐龙们就这样脆弱地在短时期内灭绝了。

翻译:省略君 来源:前十网