探索恐龙灭绝的十大理论(上)

About 66 million years ago the Cretaceous–Paleogene (K–Pg) extinction event wiped out about 80% of life on Earth, and no one is exactly sure what caused it. Many species, most famously the dinosaurs, were annihilated, while many of the survivors underwent radical transformations. Scientists have long debated the cause of one of the biggest mass extinctions in history, and while they've reached some general consensus no one is 100% certain which of the following is the cause.

大约六千六百万年前，白垩纪第三纪（K-Pg界限）灭绝事件使地球上80%的物种都消失殆尽，但没有人能确切地道出原因。许多物种，甚至包括赫赫有名的恐龙，都在这次事件中灭绝了，而幸存物种们则在这次毁灭性事件中经受了彻底的演化。长期以来，对于这件史上最大规模之一的灭绝事件发生的原因，科学家们一直争论不休，然而他们已达成初步共识——没有人敢100%的确定以下就是灭绝事件发生的原因。

roid

10.陨石撞击说

Many of the other theoretical causes of extinction stem from an asteroid impact, and an impact event is the leading theory as to what killed the dinosaurs. Called the Alvarez hypothesis, it was developed by Nobel Prize winning physicist Luis Alvarez, his geologist son Walter Alvarez and two chemists, Frank Asaro and Helen Michels. The team discovered incredibly high levels of iridium in the sedimentary layers where the Cretaceous–Paleogene boundary is found. Iridium is uncommon in the Earth's crust, but it is common on asteroids.

关于灭绝事件的成因，科学家们提出了各种假说。很多人认为此次灭绝事件和恐龙灭绝都源于行星撞击地球。诺贝尔物理学奖得主路易斯·阿尔瓦雷茨，他的地理学家儿子沃尔特·阿尔瓦雷茨，及另外两位化学家弗兰克·阿萨罗和海伦·米歇尔斯共同提出了阿尔瓦雷茨假说（即小行星撞击理论）。他们发现，在白垩纪与第三纪交接地层（K-T界限）中，铱的含量高于正常标准。铱元素在地壳中并不多见，但在小行星中却很普遍。

There was only one problem — if an asteroid hit Earth, where was the crater? Well in 1990, 10 years after the theory was published, researchers found the Chicxulub crater in Mexico. It's believed that is was made by an asteroid that was about 110 miles wide and about six across — roughly the dimensions that Alvarez and his team had calculated. It's believed that after the asteroid hit it sent dust up into the atmosphere that blocked the sun for decades. This would have caused massive climate change. Adding to the darkness was ash and smoke, as wildfires would have started from debris re-entering the atmosphere. All of these factors would come together to make life impossible for dinosaurs.

那么问题来了——如果是小行星撞击了地球，那陨石坑在哪儿？1990年，也就是这一假说发表的10年后，研究人员在墨西哥发现了希克苏鲁伯陨石坑。阿尔瓦雷茨和他的团队粗略的计算出这个陨石坑的容积——约有110英里长，6英里宽。科学家们认为，行星的撞击事件将大量灰尘升至大气层中，遮蔽了阳光数十年，从而导致大规模的气候变化。另外，火山灰与烟雾类的暗物质和残骸中产生的磷火也会再次进入大气层。所有这些因素融合在一起就导致了恐龙最终的灭绝。

al Firestorm

9.火焰风暴说

While most scientists believe that it was an asteroid that wiped out the dinosaurs, there's much debate as to what exactly the asteroid did when it hit Earth. One theory is that it started an unstoppable wall of fire that engulfed the entire planet. The argument is that when the asteroid hit, it sent vaporized rock particles above the atmosphere. There, the particles would have formed into grains of sand and then re-entered the atmosphere. The particles would have been incredibly hot, turning the sky red and making the atmospheric temperature 2700 F. This would have made the air above the point of impact act like a broiler, and everything below it would have caught fire in a blaze that would proceed to spread around the entire world. The researcher who came up with the theory said it would have been like a one-megaton bomb going off every four miles all over the Earth. Only animals that could burrow or go underwater would have been saved.

尽管很多科学家认为行星撞击是导致恐龙灭绝的罪魁祸首，但对于小行星撞击地球时的具体情况也是众说纷纭。有一种说法认为，行星撞击引发了难以扑灭的熊熊大火并吞噬地球上的每一寸土地。这个论点是指，当行星撞击地球时，蒸发岩粒子会喷出大气层，在大气层以外的地方组成无数沙粒后再重回大气层。这些粒子炽热无比，将天空烤成红色，使大气中的温度高达2700华氏摄氏度。受上述影响 ，空气变得酷热无比，像是随时都可能爆发一场大火，蔓延至整个地球表面。提出这一假说的研究人员称，那种场景像每四英里就有一百万吨的炸弹在地球上同时爆炸一样，只有穴居动物和水生生物才能得以存活。

rcanes

8.超级飓风说

Using a computer simulation, a MIT Professor theorized a super hurricane (known as a hypercane) could have theoretically occurred if an asteroid caused a 40-50 mile area of the ocean to heat to 120 F. This would have created hurricanes so powerful that winds would have reached speeds of over 600 mph. For comparison, the most powerful storm known to human history was Typhoon Tip, which made landfall on October 12, 1979. Wind speeds reached 190 mph, less than a third of the wind speed during a hypercane.

麻省理工学院的教授曾提出一个超级飓风的理论，即通过计算机模拟，当陨石撞击地球时，可以使40到50英里的海域温度理论上瞬间升高到120华氏摄氏度。这个飓风威力无穷，其风速可达到600英里/小时。相比而言，目前史上最强劲的飓风是于1979年11月12日登陆的台风泰培，其风速为190英里/小时，却也不及超级飓风风速的三分之一。

As long as the conditions exist to create them, hypercanes will keep forming, meaning the dinosaurs possibly contended with a number of these storms. However, the real danger is the height of the storm, which would have been 40 miles. This would have brought water into the stratosphere and deteriorated the ozone, which would have killed off any creatures that couldn't find shelter until the ozone reformed.

只要条件具备，超级飓风就会不断形成，这也就意味着恐龙可能得一直同大量这样的风暴作斗争。然而真正的危险则在于超级飓风那约莫40英里的高度，它会把地面上的水带至大气平流层，并恶化臭氧层，从而让数以万计的生物因找不到栖息地而灭绝，直到臭氧层重新形成为止。

ual Extinction and Mammal Competition

7.物种斗争说

A less dramatic theory is that the dinosaurs weren't killed off with one single blow, but died off gradually over the course of millions of years thanks to competition from mammals. Mammals, which were starting to become more complex beings, could have been better at finding food and dealing with changes in the environment.

另一个比较没那么引人注目的理论是说，恐龙并非是一次性灭绝的，而是在数百万年间，由于哺乳动物之间的相互竞争而逐渐灭绝。哺乳动物，就是那些正逐渐进化成高级物种的生物，他们本可以是具有更强猎食能力和应变能力的物种。

A major difference between mammals and dinosaurs is that mammals don't lay eggs. A newborn dinosaur was small but could grow to a massive size, meaning they would need a lot of food. Conversely, mammals didn't need much food and could therefore flourish much easier. And since mammals carry their children in a womb, it would have been much safer than laying an egg that would be vulnerable to predators. This theory would explain why dinosaurs died out but mammals survived the extinction event.

而恐龙和哺乳动物之间最大的区别就是，哺乳动物不下蛋。刚出生的恐龙虽然很小，但可以长得巨大，这也就意味着它需要很多的食物。相反的，哺乳动物不需要太多的食物，因而繁殖起来更加容易。哺乳动物的子宫是繁殖下一代的地方，这与易遭受掠食者的孵蛋行为比起来，子宫育儿的方式更加安全。这个理论也许对于为什么恐龙在灭绝事件中灭绝，而哺乳动物却存活下来，做了最好的解释。

inental Drift

6.大陆漂移说

The dinosaurs are thought to have first appeared during the Mesozoic era, which was 248 to 65 million years ago. Scientists divide that era into the Triassic, Jurassic and Cretaceous periods. During the Triassic, all the continents were in one giant landmass known as Pangea. During the Jurassic, Pangea broke in half and started drifting apart. By the time the Cretaceous rolled around, which is when the K-Pg extinction occured, the two continents had broken up even more, getting closer to the continents we know today.

恐龙被认为是在大约2480年到6500万年前中生代出现的生物，科学家把这段时间分为三叠纪，侏罗纪和白垩纪三个阶段。在三叠纪的时代，所有的大陆是连在一起的，被称为泛大陆（盘古大陆）。在侏罗纪时代，泛大陆一分为二，部分开始漂移。到了白垩纪时代，就是当白垩纪古新世时期，两块分开的大陆又被分成了好多块，同目前的大陆概况很接近。

The drifting of the continents would have been devastating to the dinosaurs, as their habitats would have changed drastically. It also would have caused a change in climate, and ocean cycles would have been altered. This would have led to an increase in violent storms that would have wrecked havoc on the environment, further limiting the dinosaurs' ability to survive.

大陆漂移的过程给恐龙带来了巨大的灾难，因为它们的生活习性也将随之急剧改变。而且在大陆漂移中，也造成了气候和海洋循环的变化。这会导致暴风骤雨越来越多，自然环境被严重破坏，进而降低了恐龙的生存能力。

翻译:省略君 来源:前十网