Two Events Blamed for Dinosaur Deaths

Two Events Blamed for Dinosaur¹ Deaths

Dinosaurs² ruled the Earth for about 160 million years. Then they disappeared.

Scientists have argued for years about what killed off the dinosaurs.

Was it the huge volcanic³ eruption⁴ 66 million years ago in what is now India? That explosion changed the Earth’s climate in a major way. Then, just 150,000 years later, a meteorite⁵ from space struck the coast of Mexico. This also caused changes to the climate.

Both catastrophic events happened during what is called the Cretaceous Period in Earth’s history.

Scientists have long debated which event caused the dinosaurs to disappear? One reason the debate continued was the failure of the scientists to find a perfect window from which to look into the past.

Seymour Island—key to the past?

But now, researchers say they have found a clear record of what happened.

The new evidence comes from Seymour Island -- an Antarctic island near the southern most part of South America. The researchers reported their findings in Nature Communications.

Sierra Peterson is a paleoclimatologist with the University of Michigan. She studies the climate from ancient times. To do that, she uses evidence from rocks and the fossilized remains⁶ of ancient creatures.

“The timing⁷ of the volcano and the meteorite are quite close together.”

Peterson says that with only 150,000 years separating them, physical evidence of the two events is so close together in the rock record that it is hard to tell them apart. But it is easier at the Antarctic island.

“At Seymour Island there’s 40 meters separating those two events. So we can really separate the influences of each one, and that’s why we can see the climatic impacts of both as two separate events.”

“It makes sense why people thought it was one or the other. And really they were both right.”

That is Andrea Dutton, a geochemist with the University of Florida. When Dutton was a student, she studied fossilized shells from Seymour Island. She examined them in an effort to understand ancient climate changes. But the results were unclear and difficult to understand.

New way to read the fossil record

The fossils were put in storage until Peterson showed up with a new technique. It identifies the kinds of carbon molecules⁹ in a shell. These molecules depend strongly on the temperature of the water when that layer of shell was formed.

What this meant is that, for the first time, scientists were able to find out the temperature record during the dinosaurs’ last days. What they discovered was that things got hot -- not once, but twice.

“At the time when the volcanism began, we found a rapid warming spike¹⁰ that had not been seen before. And we also found at the boundary itself, when the meteorite hit, we also saw another warming spike.”

It is what the researchers are calling a “one-two punch.” First, the dinosaurs were hit by acid rain and volcanic dust after the huge volcanic eruption. Dutton says things got a lot worse with the sudden temperature increase that followed.

“Certainly these clams¹² that we were studying and the other fauna¹³ in this system, they had experienced temperatures this warm earlier in the Cretaceous. But what happened here is the temperature increase was so fast that it was a large stress that they weren’t able to adapt that quickly to the large temperature change.”

Dutton says she and Peterson are not necessarily saying that the warming is what killed everything at the time. But it could have made things worse. It could have been responsible for part of the dinosaurs disappearing.

After that, the creatures that survived the first warming spike suffered another blow — a huge rock from space hitting Earth. That impact also caused a jump in temperatures.

What does this mean for us today?

So why is it important to know about how and why the dinosaurs died off so long ago?

Peterson and Dutton suggest people should pay close attention to their work. They say the effects of fast climate change in the Cretaceous period are similar to what scientists are seeing now from climate change.

Peterson says the volcano eruption before the meteorite increased pressure on Earth’s environment. In that same way, the carbon dioxide gas emissions¹⁴ from human activities are affecting the environment today.

“We are already seeing extinctions and certain organisms being under a lot of environmental stress, reduced habitat, things like that. All of the same things we are observing today would have been in play in the Cretaceous as well. And so, you know, I guess fingers crossed for no meteorite impact.”

And so it seems we might have a lot of learn from the dinosaurs’ disappearance¹⁶.

Words in This Story

catastrophic – adj. of the nature of a catastrophe¹⁷, a disaster

molecule⁸ – n. the smallest possible amount of a particular substance that has all the characteristics of the substance

layer – n. one thickness of something laid over another

rapid – adj. very fast

spike – n. a sudden, very fast increase in something

boundary – n. something that shows where an area ends and another begins

“one-two punch” – idiom phrase. getting hit, or punched, but one thing, and then another

clam¹¹ - n. a type of shellfish that lives in sand or mud that has a shell in two parts (called bi-valves) and can be eaten cooked or raw

fauna - n. all the animals that live in a particular area, time or environment

impact – n. place where something hits another

extinction¹⁵ – n. when something has died out completely

1 dinosaur   

n.恐龙

参考例句：

• Are you trying to tell me that David was attacked by a dinosaur?你是想要告诉我大卫被一支恐龙所攻击？
• He stared at the faithful miniature of the dinosaur.他凝视著精确的恐龙缩小模型。

2 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

3 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

4 eruption   

n.火山爆发；（战争等）爆发；（疾病等）发作

参考例句：

• The temple was destroyed in the violent eruption of 1470 BC.庙宇在公元前1470年猛烈的火山爆发中摧毁了。
• The eruption of a volcano is spontaneous.火山的爆发是自发的。

5 meteorite   

n.陨石；流星

参考例句：

• The meteorite in Jilin Exhibition Hall is believed to be the largest in the world.吉林展览馆的陨石被认为是世界上最大的。
• The famous Murchison meteorite smashed into the Australian ground in 1969.1969年著名的默奇森陨石轰然坠落在澳大利亚。

6 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

7 timing   

n.时间安排，时间选择

参考例句：

• The timing of the meeting is not convenient.会议的时间安排不合适。
• The timing of our statement is very opportune.我们发表声明选择的时机很恰当。

8 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

9 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

10 spike   

n.长钉，钉鞋；v.以大钉钉牢，使...失效

参考例句：

• The spike pierced the receipts and held them in order.那个钉子穿过那些收据并使之按顺序排列。
• They'll do anything to spike the guns of the opposition.他们会使出各种手段来挫败对手。

11 clam   

n.蛤，蛤肉

参考例句：

• Yup!I also like clam soup and sea cucumbers.对呀！我还喜欢蛤仔汤和海参。
• The barnacle and the clam are two examples of filter feeders.藤壶和蛤类是滤过觅食者的两种例子。

12 clams   

n.蛤；蚌，蛤( clam的名词复数 )v.（在沙滩上）挖蛤( clam的第三人称单数 )

参考例句：

• The restaurant's specialities are fried clams. 这个餐厅的特色菜是炸蚌。 来自《简明英汉词典》
• We dug clams in the flats et low tide. 退潮时我们在浅滩挖蛤蜊。 来自辞典例句

13 fauna   

n.(一个地区或时代的)所有动物，动物区系

参考例句：

• This National Park is an area with unique fauna and flora.该国家公园区域内具有独特的动物种群和植物种群。
• Fauna is a biological notion means all the animal life in a particular region or period. 动物群是一个生物学的概念，指的是一个特定时期或者地区的所有动物。

14 emissions   

排放物( emission的名词复数 )； 散发物（尤指气体）

参考例句：

• Most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
• Dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。

15 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。

16 disappearance   

n.消失，消散，失踪

参考例句：

• He was hard put to it to explain her disappearance.他难以说明她为什么不见了。
• Her disappearance gave rise to the wildest rumours.她失踪一事引起了各种流言蜚语。

17 catastrophe   

n.大灾难，大祸

参考例句：

• I owe it to you that I survived the catastrophe.亏得你我才大难不死。
• This is a catastrophe beyond human control.这是一场人类无法控制的灾难。