Why did dinosaurs become extinct?

German scientists recently suggested that the extinction of dinosaurs was caused by the bad "space weather" at that time, that is, the strong particle flow from the universe broke into the earth's atmosphere, causing drastic changes in the earth's climate and leading to the extinction of dinosaurs.

According to the German magazine Science Illustrated, Joerg Farr, a professor from the Institute of Astrophysics in Bonn, said that the earth fell into a strong cosmic particle flow "storm" 60 million years ago. When encountering such a storm, various particles entering the earth's atmosphere at high speed will reach hundreds of times as usual, tearing the molecules in the atmosphere into condensation nuclei necessary for the formation of rain, which will eventually lead to the thickening of clouds in the earth's atmosphere, frequent rainfall and a sudden drop in temperature.

Scientists believe that the explosion of cosmic particle flow caused the drastic change of the earth's climate conditions, and dinosaurs that could not adapt to this climate change became extinct in a short time.

In the Mesozoic era in the history of the earth, there were many kinds of reptiles-dinosaurs. Hundreds of dinosaur fossils have been found in the world, and such a huge animal group that ruled the earth for10.6 billion years suddenly collapsed at the end of Cretaceous. Wrote a puzzling chapter in the history of biology

So far, all kinds of explanations about the extinction of dinosaurs can't be justified. In recent years, the hypothesis that asteroids hit the earth put forward by American physicist Luis Alvarez has attracted much attention. He found that the content of trace element jujube iridium in the upper stratum of the late Cretaceous in gubbio suddenly increased by more than 30- 160 times compared with other strata, and then people came to the same conclusion from sampling tests all over the world, and the abnormal increase of iridium in the late Cretaceous strata was indeed universal. So Alvarez thinks that an asteroid with a diameter of about 10 km hit the earth at the end of Cretaceous, and the dust produced covered the sky. It caused great changes in the surface climate environment and led to the extinction of dinosaurs. However, there are many doubts about explaining the increase of iridium content in rock formations and the extinction of dinosaurs caused by the impact of asteroids on the earth.

1. Asteroids are generally composed of silicon and iron, so it is impossible for such a huge asteroid to fall to the surface of the earth even after a long time, and such a large meteorite has never been found on the earth;

2. At the end of Cretaceous, most rock formations were igneous rocks formed by lava cooling, and sedimentary rocks formed by dust accumulation only occupied a small part of the surface. Can the dust raised by the asteroid impact bury most of the animals and plants on the earth in rocks thousands of meters deep?

3. Can iridium contained in asteroids be evenly distributed and cover the whole earth's surface? Iridium also exists deep in the earth. Why only speculate that iridium comes from outside the earth and not from inside it?

As we know, thermonuclear reactions inside the earth will continuously accumulate enormous energy. Once the crust can't bear it, the internal pressure will break through the crust and suddenly release to form a big explosion. Iridium date, an element mainly existing in the core of the earth, was brought to the surface of the earth's crust by lava eruption during the Big Bang. It is recognized that the clay layer at the end of Cretaceous was formed by a large amount of volcanic dust accumulation. Therefore, the general increase of iridium content in the strata at the end of Cretaceous proves that the crust erupted violently at that time.

Fossil archives tell us that most dinosaurs died and most dinosaur eggs were produced at the end of Cretaceous, and all the dinosaurs and dinosaur eggs found were preserved in the stratum under the thin clay layer rich in iridium, which is consistent with the time of a series of global crustal structural changes such as large-scale orogeny at the end of Cretaceous recognized by geologists.

In recent years, hundreds of protoceratops and Ankylosaurus fossils were unearthed in Bayin Mandu Lake stratum in Inner Mongolia at the end of Cretaceous, and a large number of complete dinosaur bones were piled up in groups. Judging from the burial posture of the remains, they died in extreme pain, including the bones of a whole group of baby dinosaurs. This scene shows that they died catastrophically, and the bodies were quickly buried in situ (in other parts of the world? What's the matter with you? m？ ⑾ What's the value? What should I do if it is difficult to swell? Are you arrogant? What happened to the bell, gauze, kang and Ye Ti? Art? Weft cutting, crow fertile field? What happened to the grave? What is the slow input of locusts into nettles? What's the problem? What's the problem? What is the agreement between you and me? Mechanical eye? Angkor? Howl ┯ Manet Mo Xie K? Yu? Hey? Where to? Secret protest? What's wrong with being a bitch? Chrysanthemum 5 What is the news that squid and locusts are calling for a thief? Hey? Lao Yu?

A large number of animals and plants reflecting the characteristics of the earth's environment at that time showed that before the end of Cretaceous, the density and thickness of the earth's atmosphere were much higher than now, the surface was relatively flat, and the world was in a very warm and humid climate. At that time, the temperature difference between the polar regions and the equator was very small. In the 1980s, Canadian geologists discovered a fossil forest in ellesmere island, which was dominated by water jackets, and there were animal fossils such as crocodiles in the forest, indicating that the polar regions used to have a tropical climate. The natural environment is the main factor that determines the existence form of life. After the Big Bang, when the hot and humid environment on which giant dinosaurs lived no longer existed, even if some of them survived, they could not adapt to the different relatively cold and dry climates in cold and warm seasons and continue to survive. So the extinction of most dinosaurs is natural.

There are also some surviving dinosaurs (mostly smaller) and some animals that have evolved into primitive birds and mammals as early as Paul's time, following the laws of natural selection and survival of the fittest. In a relatively harsh environment, after 70 million years of continuous evolution, most species have changed their original forms, from cold-blooded animals to cold-tolerant warm-blooded animals (birds, mammals and humans). Of course, after every large-scale species evolution, some species will remain intact. For example, after fish evolved into amphibians, fish continued to survive, and very few reptiles (crocodiles, scorpions, etc. ) still maintains the original form of dinosaurs 70 million years ago.

The biological remains in the earth's rock strata reveal that in the history of biological evolution, there will be a mass extinction every once in a while. The extinction of dinosaurs at the end of Cretaceous is not the only disaster in the history of biological evolution. In an earlier era, there was a "Cambrian Big Bang" phenomenon in which most invertebrates suddenly appeared in a short time. Just like the evolution of organisms from single cell to multi-cell, reptiles to mammals, it needs an evolutionary process (such as 1984, the discovery of Chengjiang fossil group in China).

So far, there is no obvious evidence that the extinction of dinosaurs was caused by asteroid impact. However, the fact that the geological structure of the earth continues to change frequently shows that the environmental "catastrophe" caused by periodic crustal structure changes has always played a leading role in the process of biological evolution. Of course, the gradual evolution of small-scale species also runs through the whole process of life evolution. Periodic celestial explosion (such as nova explosion) is an indispensable link in the evolution of all planets, including the earth. Marine fossils and seabed minerals in those mountains are the best explanation for the end of the dinosaur era caused by the drastic changes in the earth's crust.

In the Mesozoic era more than 200 million years ago, a large number of reptiles lived on land, so the Mesozoic era was also called the "reptile era", and the earth was widely occupied by vertebrates for the first time. At that time, the earth's climate was warm and there were dense forests everywhere. Reptiles have enough food, and gradually flourish, with more and more kinds. They constantly differentiate into various reptiles, some become turtles today, some become crocodiles today, some become snakes and lizards today, and some evolve into mammals all over the world today.

Dinosaurs are the largest reptiles. They are very suitable for living in swamps and shallow lakes. At that time, the air was warm and humid, and food was easy to find. So dinosaurs ruled the earth for tens of millions of years, but for some reason, they suddenly became extinct in a short time 65 million years ago. Today, people only see a large number of dinosaur fossils left at that time.

People are still studying the reasons for the extinction of dinosaurs. For a long time, the most authoritative view is that the extinction of dinosaurs was related to a big meteorite 65 million years ago. According to research, an asteroid with a diameter of 7- 10 km once fell on the earth's surface, causing a big explosion, throwing a lot of dust into the atmosphere, forming dust fog that covered the sun, leading to the temporary suspension of plant photosynthesis and the extinction of dinosaurs.

The asteroid impact theory quickly gained the support of many scientists. 199 1 year, a meteorite impact crater was discovered in Yucatan Peninsula, Mexico, which further confirmed this view. Today, this view seems to be conclusive.

However, many people are skeptical about this asteroid impact theory, because the fact is that frogs, crocodiles and many other temperature-sensitive animals survived the Cretaceous period. This theory can't explain why only dinosaurs died. So far, scientists have put forward more than a dozen hypotheses about the causes of dinosaur extinction, and the more exciting and dramatic "meteorite impact theory" is just one of them.

In addition to the "meteorite impact theory", the main viewpoints about the extinction of dinosaurs are:

First, the theory of climate change. 65 million years ago, the earth's climate changed suddenly and the temperature plummeted, which led to the decrease of oxygen content in the atmosphere and dinosaurs could not survive. Some people think that dinosaurs were cold-blooded, without hair and warm organs, unable to adapt to the decline of the earth's temperature, and all of them froze to death.

Second, the theory of species struggle. At the end of the dinosaur era, the first small mammals appeared. These animals are rodent carnivores and may feed on dinosaur eggs. Due to the lack of natural enemies, more and more small animals finally ate dinosaur eggs.

Third, the theory of continental drift. Geological research has proved that there was only one continent on the earth when dinosaurs lived, and that was Pangea. Due to the change of the crust, the Jurassic continent split and drifted, which eventually led to the change of environment and climate and the extinction of dinosaurs.

Fourth, the theory of geomagnetic variation. Modern biology has proved that the death of some creatures is related to magnetic fields. When the earth's magnetic field changes, creatures sensitive to the magnetic field may lead to extinction. It can be inferred that the extinction of dinosaurs may be related to the change of the earth's magnetic field.

Five, angiosperm poisoning theory. At the end of the dinosaur era, gymnosperms on the earth gradually became extinct, replaced by a large number of angiosperms, which contained toxins that gymnosperms did not have. Giant dinosaurs ate a lot, and a large number of angiosperms led to excessive accumulation of toxins in the body and finally poisoning.

Sixth, the theory of acid rain. There may have been strong acid rain at the end of Cretaceous, which dissolved trace elements including strontium in the soil. Dinosaurs ingested strontium directly or indirectly through drinking water and food, which led to acute or chronic poisoning and eventually died in batches.

There are many hypotheses about the extinction of dinosaurs. However, these hypotheses have more supporters in the scientific community. Of course, each of the above statements has some imperfections. For example, the "climate change theory" does not clarify the reasons for climate change. After investigation, it was found that some small osteophytes in dinosaurs could compete with early small mammals, so there were loopholes in the theory of species struggle. In modern geology, the "continental drift theory" itself is still a hypothesis. "Angiosperm poisoning theory" and "acid rain theory" also lack sufficient evidence. Therefore, the real reason for the extinction of dinosaurs remains to be further explored.