There are many kinds of dinosaurs, and their shapes and habits are also very different. Among them, the big one can be as big as dozens of elephants combined; Small, but almost like a chicken. As far as eating habits are concerned, dinosaurs have mild vegetarians and fierce carnivores, and there are omnivorous dinosaurs that eat both vegetarians and vegetarians.
The real cause of dinosaur extinction has been debated since ancient times, but there is no definite statement, so it is still an unsolved mystery. Here, only some well-known statements are described as follows:
1. meteorite collision theory;
65 million years ago, a huge meteorite hit the earth, making the dinosaurs that lived in King's Landing 1 100 million years extinct. This theory was put forward by four scientists, including Dr. Luis Albales of the University of California, Berkeley.
This huge meteorite is about 10 km in diameter. The crater caused by the impact is 200 kilometers in diameter. The energy generated by the impact, if converted into explosives, is equivalent to one million tons. Dust diffuses into the stratosphere through the atmosphere. It made the earth dark for several months. During this period, many creatures, led by dinosaurs, became extinct.
2. Comet collision theory;
The basis of comet collision theory is paleontologist-David? Laup and John? Sepkovsky's argument that "the extinction of paleontology occurs every 26 million years" is a beginning. Louis? Albalez handed this argument and his own theory to the astrophysicist-Charlie? Milla, later Milla thought it was because of the gravity of Nemesis, and Nemesis, the half star of the sun, periodically pushed comets to the earth.
3. Theory of orogeny;
At the end of Cretaceous, the swamp was dried up by orogeny, and many dinosaurs whose home was swamp could no longer survive. Because of the changes in the post-Qi period, plants also changed, and herbivorous dinosaurs could not adapt to new foods and died out one after another. The herbivorous dinosaurs became extinct, and the carnivorous dinosaurs lost their dependence. Therefore, they are also extinct. This extinction process lasted 65,438+0,000-20 million years. By the end of Cretaceous, it was extinct on the earth.
4. Climate change theory:
Due to plate movement, ocean currents have changed, which has led to great changes in the climate. The cold climate killed plants and dinosaurs died for lack of food.
5. Volcanic eruption theory:
Because of the volcanic eruption, a large amount of carbon dioxide was ejected, which caused the greenhouse effect of the earth and caused food death. In addition, the volcano spewed fire, which led to the release of a large amount of salt, the destruction of the ozone layer, and harmful ultraviolet radiation on the earth's surface, leading to extinction.
The theory of ocean ebb tide with intransitive verb;
According to Barker, when the ocean ebbs and borders the land, creatures will contact each other, which will lead to the extinction of some species. For example, kangaroos can live on the island continent of Europe, but they will die when they meet other animals on the South American continent.
In addition to this relationship between eating and being eaten, there are infectious problems such as diseases and parasites.
Seven. Warm-blooded animals say:
Some people think that dinosaurs were warm-blooded animals, so they couldn't stand the cold weather in the late Cretaceous and couldn't survive. Because even though dinosaurs were warm-blooded animals, their body temperature was still not high, which may be similar to that of living sloths, and to maintain such a body temperature, they could only live in a tropical climate. At the same time, the dinosaur's respiratory organs were not perfect and could not fully supplement oxygen. They don't have thick hair to avoid hypothermia, but they easily lose a lot of heat from their long tails and feet. The difference between warm-blooded animals and cold-blooded animals is that if the body temperature drops below a certain range, it will consume body energy to raise the body temperature and the body will soon become weak. They are too big to go into caves to avoid the cold, so if the cold days last for a few days, they may freeze to death because of exhaustion.
Eight. Fratricidal theory:
Some people think that the real reason for the extinction of dinosaurs is the result of their killing each other-carnivorous dinosaurs ate herbivorous dinosaurs, carnivorous dinosaurs increased, herbivorous dinosaurs naturally became less and less, and finally disappeared. Carnivorous dinosaurs killed each other because they had no meat to eat, and finally died together.
Nine. Oppression theory:
The number of dinosaurs increased rapidly, which led to the extinction of herbivorous dinosaurs with limited plants, and then carnivorous dinosaurs that ate herbivorous dinosaurs died because of lack of food. Question: Why did dinosaurs suddenly increase after about 200 million years of ecological balance? The key to the establishment of this theory has directly caused many scholars to review the reasons for the abnormal increase in dinosaur production. )
10. The mammalian prisoner said:
In the second half of Mesozoic, the ancestors of mammals already existed. According to fossil records, mammals at that time were very small and the number was very limited. It was not until the late Cretaceous that this number began to increase rapidly. It is speculated that they are omnivorous animals that feed on insects. After the discovery of dinosaur eggs, these small mammals kept eating dinosaur eggs.
My opinion: Is this really the case? If mammals beat dinosaurs, then with the increase of mammalian fossils, dinosaur fossils should gradually decrease, but in fact there is no such phenomenon of fossil alternation. In other books, the real increase in mammalian fossils was after the end of the dinosaur era. Moreover, dinosaur fossils suddenly disappeared. Therefore, the theory that dinosaurs were wiped out by mammals cannot be established. )
1 1. species aging theory:
People think that the dinosaur's body was too big because it flourished for hundreds of millions of years. Moreover, horns and other bones are extremely developed, which brings great inconvenience to life and eventually leads to extinction.
Lei Long, the most representative dinosaur, was 25 meters long and weighed 30 tons. Because of his huge size, he lost his ability to live. In addition, Triceratops and others also went to the road of self-destruction because of their expanding three horns and unusually developed bones to protect their heads.
My opinion: not all dinosaurs are so huge, but there are also small dinosaurs with a body length of only about one meter. In addition, there are bones like deer and dinosaurs that can run briskly. But why did this dinosaur die out at the same time? In addition, in cold-blooded animals, abnormally developed bones and other parts should be able to absorb external temperature and release internal heat to regulate body temperature, which has a very favorable function. Therefore, I suspect that the extinction of dinosaurs was due to the aging of species. )
Twelve. Alkaloid theory:
According to this theory, flowering plants began to appear in the Cretaceous, the last period of dinosaur existence, and some of them contained toxic alkaloids. Dinosaurs died of poisoning because of eating a lot of food. Because mammals can distinguish poisonous plants by taste and smell, but dinosaurs don't have this ability.
However, plants containing alkaloids did not suddenly appear in the late Cretaceous, and they were already visible five million years before the extinction of dinosaurs. This theory cannot explain why dinosaurs survived during this period.
In addition to the above twelve statements, there are other less well-known statements, such as "infectious diseases", "radiation from the universe or supernova explosion", "not riding Noah's Ark" and "solar system vibration". As for which statement is the best, it depends on everyone's idea, and there is no right or wrong. After all, the mystery of dinosaur extinction has not really been solved!
Who first discovered dinosaurs?
The story of prout-Garon-Garon
Mrs Mantell found the story of dinosaurs really romantic. Mr Mantell was able to explore the ownership of dinosaurs with a rigorous and realistic attitude, which was indeed the first step for human beings to study dinosaurs scientifically and understand them.
However, in history, humans discovered dinosaur fossils very early, but at that time, due to limited knowledge, they could not be correctly explained.
As early as 1000 years ago, during the Jin Dynasty in China, dinosaur fossils were discovered in Wucheng County, Sichuan Province. However, people at that time did not know that it was the remains of dinosaurs, but regarded it as the bones left by the legendary dragon.
According to the clues found in the historical novel Mr. milken's Wife, a researcher named Husted from the University of Reading in England recently announced that he had finally discovered the following fact: in 1677, an Englishman named prout-Garonne-Garonne wrote a natural history book about Oxford. In this book, prout-Garonne-Garonne describes a huge fossil leg bone found in a quarry in the parish of Karovilla. Prout-Garonne-Garonne drew a good illustration of this fossil, and pointed out that this thigh bone is neither cow's nor horse's nor elephant's, but belongs to a giant bigger than them.
Although prout-Garonne-Garonne didn't realize that this fossil was a dinosaur or even associated with reptiles, the specimen he described with words and illustrations was identified by later paleontologists as the thigh bone of a dinosaur called Megalodon, and this fossil was discovered before Iguanodon was discovered in Mantels 145. Therefore, Hastert thinks that prout-Garonne-Garonne should be the first discoverer and recorder of dinosaur fossils.
The origin of the name "dinosaur"
In fact, the history of human discovery of dinosaur fossils must have a long history. Long before Mantel and his wife discovered Iguanodon, Europeans knew that there were many grotesque huge bone fossils buried underground. However, people didn't know exactly where they belonged at that time, so they were always mistaken for "the remains of giants". As for China, as early as more than 2,000 years ago, we began to collect large ancient animal fossils unearthed underground for medicinal purposes, and called these fossils "keels". Who can be sure that the name "keel" has nothing to do with the discovery of dinosaur fossils?
The oldest reptile fossils can be traced back to the Paleozoic Pennsylvanian period (365,438+million years ago-275 million years ago). Tracing back to the source, it evolved from amphibians. Amphibian eggs need to develop in water. Reptiles have evolved eggshells to prevent water from escaping. This major reform enables reptiles to survive without water.
By the Mesozoic era from 225 million years ago to 65 million years ago, reptiles had become the masters of the earth, so the Mesozoic era was also called the era of reptiles. Large reptile dinosaurs appeared in the early Mesozoic. Herbivorous Liang Long and Lei Long are the largest land animals. Tyrannosaurus rex is a carnivorous dinosaur. There are also ichthyosaurs living in the sea and pterosaurs living in the air.
Reptiles have flourished on the earth for about 65.438+0.5 billion years. Among the animals of this era, dinosaurs are the most famous. When people mention dinosaurs, they will see a huge and fierce animal. In fact, there are also small and docile dinosaurs among dinosaurs.
Dinosaur is a kind of vertebrate reptile, which was once produced in the Mesozoic land swamp and had a long neck and tail. The hind limb is longer than the forelimb and has a tail. Among them, several species are carnivorous, and several species are herbivorous. They are huge and can be considered as the largest terrestrial animals. Its physique is like the oldest crocodile and beak in lower species, and slightly similar to birds in higher species.
The study of dinosaurs depends entirely on fossils. Paleontologists infer their shapes and habits from their fossils. According to paleontologists, dinosaurs are like living animals: there are big ones and small ones; Some people walk on two legs; Some people walk on four legs; Some eat plants, some eat animals; Some skin is smooth, and some skin has scales or bone plates. Their common similarity is that all dinosaurs had small brains and laid eggs on land (as do all reptiles).
Classification of dinosaurs and introduction of various types of dinosaurs;
(1) Lei Long:
Some dinosaurs had huge bodies, such as Lei Long. During the Jurassic period, the climate on the earth was warm and humid, and there were lush forests everywhere. Because of these rich plant foods, herbivorous dinosaurs were able to thrive. After that, Lei Long was also active in the North American Plain.
Lei Long weighs about 35 to 50 metric tons and has thick legs like tree trunks. With a long neck, it stands as high as seven stories and can be said to be the largest animal in the world. Although Lei Long's body is surprisingly huge, her temperament is very gentle. She usually feeds on plants in temperate forests and sometimes walks into swamps. Because of the buoyancy of water, she can reduce the heavy burden on her body and avoid the attack of fierce carnivorous dinosaurs like Allosaurus.
(2) three dragons:
Bone plates and fragments of Stegosaurus and Ceratosaurus can only be used as passive defense, but they can't fight back. Only when the Rocker Dragon appeared did the situation change gradually. Sanlong is the largest of all sauropods, with two spear-shaped horns on its head, and the other horn protrudes between its eyes and nostrils. Such a sharp weapon, even the most terrible carnivorous dinosaur will make it three points.
③ Stegosaurus:
Stegosaurus appeared10.5 billion years ago, characterized by two ribs on the back and spikes on the tail. Stegosaurus was a herbivorous dinosaur and moved slowly. Its bone plate and spikes on its tail became the best weapon against carnivorous dinosaurs.
④ Ankylosaurus:
Stegosaurus was protected by a bone plate, but it was still fragile where the bone plate could not cover it. When stegosaurus gradually disappeared, Ankylosaurus covered with bone plates took its place. Ankylosaurus is like an invincible tank car, even Tyrannosaurus rex can't do anything about it.
⑤ Tyrannosaurus Rex:
Tyrannosaurus Rex is the largest and most ferocious carnivorous dinosaur. Tyrannosaurus rex appeared at the end of the dinosaur era about 80 million years ago. Tyrannosaurus rex's body is 14 meters high and weighs about 10 metric ton. Its hind feet are thick and strong, and can even support a rhinoceros.
From the fossils of Tyrannosaurus Rex, it is found that every tooth is as big as an adult's palm, and even its eyes are bigger than a human head. Although most of Tyrannosaurus rex's body is surprisingly large, its forelimbs are so small and short that it is impossible to send food to its mouth. The killer dragon has the same habit as Tyrannosaurus Rex, and it is a fierce animal.
[6] Duck crested dragon:
Like Tyrannosaurus rex, the duck-crowned dragon also appeared at the end of the dinosaur era. The most special thing about the duck-crowned dragon is its head. Its flat and long jawbone looks like a duck's mouth, so it has the name of the duck's crown dragon. In the past, people thought that the life of duck-crowned dragon was similar to that of duck. It swims in the water and feeds on plants in the water. Later, when scientists studied the fossils of the duck-crested dragon, they found that they did not eat aquatic plants for a living, but lived in trees on the shore, and the goose-crested dragon had the same habit.
iguanodon
1822 One day in March, it was very cold, but Mr. Mantel went out to see the patient as usual. The lady is waiting for her husband to come back at home. She is always worried that he will catch cold. Later, Mrs Mantell couldn't sit still, so she took her husband's clothes and went out in the direction of his house calls. She is walking on a road under construction, and the newly cut steep walls on both sides of the road reveal layers of rocks. She habitually walked and observed the newly exposed rock formations on both sides. Suddenly, a shiny thing caught her attention. "What is this?" While talking to herself, she stepped forward to observe carefully. Wow! It turned out to be some strange-looking animal tooth fossils. These fossil teeth are so big that Mrs Mantell has never seen such big teeth. The excitement of discovery made Mrs Mantell forget about sending clothes to her husband. She carefully took these fossils out of the rocks and took them home.
Later, Mr mantel returned home. He was shocked when his wife gave him the newly collected fossils. He has seen many ancient animal tooth fossils, but none of them can be similar to such a large and strange tooth.
Soon after, Mr mantel found many such tooth fossils and related bone fossils near the place where the fossils were found. In order to find out what animals these fossils belong to, Mr Mantell took them to the French naturalist Zhu Ye Wei and asked the most famous scholars in the world to identify them.
To tell the truth, Ye Wei has never seen this kind of fossil, and all the books and papers written by senior scientists he has read have never mentioned this kind of fossil. However, Ju Ye Wei made a judgment based on his rich knowledge of zoology. He thinks that the teeth belong to rhinoceros and the bones belong to hippopotamus, and they are not too old.
Mr Mantel is skeptical about Zhu Ye Wei's assessment, and thinks that Zhu Ye Wei's conclusion is too hasty. He decided to continue his research. From then on, whenever he had the chance, he went to museums all over the country to compare specimens and consult materials.
One day two years later, he met a naturalist who worked in the Royal College Museum in London. He is studying an iguana, a modern lizard living in Central America. Therefore, Mr Mantel took these fossils to the Royal College Museum in London, and compared them with the teeth of iguanas collected by naturalists, and found that they were very similar. Mr mantel, who was overjoyed, concluded that these fossils belonged to an extinct ancient reptile similar to an iguana and named them "the teeth of an iguana".
Later, with the discovery of more and more fossil materials, people have a deeper understanding of these ancient animals. We know that the so-called "iguana's teeth" are actually a member of a wide variety of dinosaur families; It does belong to reptiles such as iguanas, but it is more closely related to real iguanas than to other dinosaurs! However, according to the biological naming rules, the Latin word of the earliest dinosaur name with scientific records has not changed, and it still means "the teeth of an iguana". However, its Chinese name was translated into Iguanodon.
So please remember: Iguanodon is the earliest recorded dinosaur in the history of science. At the same time, don't forget the name Mantel and his wife who loves nature.
Who first discovered dinosaurs-Mr. and Mrs. Mantel
There is a small place called Lewis in Sussex in the south of England. 180 years ago, there once lived a village doctor named Mantel. This Mr mantel is full of curiosity about nature, and especially likes collecting and studying fossils. In addition to practicing medicine and treating diseases, he often takes his wife to climb mountains and wade to find and collect fossils, and his footprints have traveled all over the exposed ravines and ridges of surrounding rock formations. With the passage of time, Mrs Mantell has also become a "friend of nature" and a master of fossil collection.
(8) parrot-billed dragon
However, it was not until the Mantels discovered Iguanodon and compared it with iguana that the scientific community initially determined that it was an extinct reptile similar to lizard. Therefore, the names of new types of dinosaurs and other ancient reptiles discovered later are all related to lizards, such as "lizards like whales" and "lizards in the forest". At the same time, these ancient animal fossils that first attracted people's attention are often huge and grotesque, which is really frightening.
With the discovery and excavation of these horrible lizard-like fossils, there are more and more kinds of them, and many naturalists begin to realize that they should be self-contained in animal taxonomy. 1842, the British paleontologist Sir Owen created a name for them in Latin. This name consists of two roots, the former means "terrible" and the latter means "lizard". Since then, the "terrible lizard" has become the general name of this large class of reptiles. They are related to each other to some extent, but they behave in different ways. We in China have both imagination and generalization, and translated this Latin name into "dinosaur".
(9) Mamen Xilong
Now we know that there are indeed many horrible giants in the dinosaur family, but there are also some small and lovely "little things". If you go to the Museum of Chinese Paleontology not far from the west of Beijing Zoo, from the parrot-billed dragon with a length of less than 65,438+0 meters to the Mamenxilong with a length of 22 meters, dinosaurs of different sizes and shapes will definitely give you a more comprehensive understanding of the dinosaur world.
Ssangyong (10)
Ssangyong has a stout body, a tall skull, a well-developed jawbone, a big mouth crack, teeth covered with teeth like sharp knives, and small serrations on the front and back edges of teeth. These characteristics show that it can tear up any captured prey and then swallow large pieces of meat into its stomach. In addition, there is a hole in the back of the eye on the skull of Ssangyong, which is used to better attach the muscles that affect the jawbone, so the bite force of Ssangyong must be very strong. Scientists speculate that Ssangyong may be the most ferocious and ferocious carnivore in the early Jurassic ecosystem.
Ssangyong dinosaur and archaeopteryx dinosaur were buried together.
Ssangyong's hind legs and claws are strong and can be used to catch and tear prey. During that time about 200 million years ago, Ssangyong often appeared in the highlands or jungles between rivers and lakes, chasing all kinds of vegetarian animals. They may also like to live alone, and sometimes they may hide in places that are not easy to be found and wait for the opportunity to attack their prey. They may even eat animal carcasses and carrion that died for various reasons like modern hyenas.
China also found the Ssangyong fossil in Jinning County, Yunnan Province.
1In August, 987, the dinosaur excavation team of Kunming Museum in Yunnan Province excavated a Yunnan sauropod dinosaur fossil in Xiyang Township, Jinning County. The news that spread like wildfire attracted people from all directions to watch. People here are all Yi people. They have never heard of any dinosaurs. But when they see the fossil fragments, some people think that this bone-shaped stone looks familiar. Some people told the excavation team that such stones were also seen on the hillside of Muganlang Village in Sunset Township.
The excavation team followed the messenger to Muganlang Village, and a pile of dinosaur spines appeared in a small ravine. They decided to dig here. A few days later, a shocking scene appeared. There are actually two dinosaurs here! Moreover, two complete dinosaur bones are twisted together, one of which is an ancient-footed dinosaur, and the other is a carnivorous Ssangyong, whose big mouth just bit on the tailbone of the former. According to this burial condition of fossils, scientists speculate that there may be two reasons for the death of these two dinosaurs: first, they both died in a desperate struggle; Another possibility is that the paleopoda has been dead for many days, and the meat on the corpse has rotted and deteriorated, while the hungry theropods have just filled their stomachs, but unexpectedly, they died of poisoning due to eating the rotten meat of the paleopoda. Judging from their calm posture, the latter is more likely.
China Shuanglong is the largest carnivorous dinosaur in the early Jurassic period, with a body length of nearly 4 meters and a sharp and long mouth. There is a crack in the front of its maxilla, which enables it to move. Scientists speculate that its favorite food is probably the internal organs of other animals, because its sharp mouth can extend into the abdominal cavity of an animal corpse. When its head extends into the abdominal cavity of a corpse, two thin crowns on its head can support the cavity wall.
Ssangyong is also a member of the fauna around the Tethys Sea, so the species found all over the world are very similar. Their fossils have also been found in modern Antarctica, which shows that the frozen and snowy Antarctica was a warm dinosaur day at that time.
extinct
In recent years, dinosaur fossils have been continuously discovered, and new species have been continuously discovered. Groups of scientists are interested in their research, and generations of children and their parents have a strong interest in these mysterious ancient creatures. Why is this?
Now we also know that dinosaurs were not lizards at all. Although they all belong to reptiles, the genetic relationship between dinosaurs and lizards is far from each other in a huge reptile family!
From the dexterous Protosaurus to the ferocious Tyrannosaurus Rex
Carnivorous theropod dinosaur
Ssangyong, the overlord in the early Jurassic
1942, a large theropod dinosaur was found in the early Jurassic strata in Arizona, USA. Because it has a pair of slender V-shaped bones on its head, scientists named it Shuanglong.
End-Mesozoic extinction
This is because many dinosaurs are too big compared with us, which makes us all have to think, why did they grow so big? It is precisely because there are so many kinds of dinosaurs and their looks are so strange that we can't help wondering how many members there are in this huge dinosaur family.
There is a more important reason, that is, why so many dinosaurs that once lived on the earth have disappeared from the earth, but they have not left their descendants, but they have left us with an unsolved mystery. This mystery always inspires us to explore and seek knowledge.
Now we know that dinosaurs died out 65 million years ago. And at that time, not only all kinds of dinosaurs that ruled the earth 1 100 million years were extinct, but also many other creatures living on the land, sea and sky on the earth suffered the same tragic fate. Also extinct in this disaster are marine reptiles such as plesiosaur, flying reptiles such as pterosaurs, relatives of land reptiles such as colorful lizards, and marine invertebrates such as ammonites and arrow stones. As for the micro-phytoplankton in the ocean, calcareous planktonic foraminifera and calcareous micro-phytoplankton have also been almost swept away. After this catastrophe, about 50% of the biological genera and almost 75% of the biological species on the earth disappeared from the earth forever.
This is really a mass extinction and catastrophe. Because of this extinction, the face of the biological world on earth changed fundamentally about 65 million years ago. This extinction marks the end of Mesozoic era, and the geological history of the earth has entered a new era-Cenozoic era.
Through unremitting efforts, scientists have analyzed and studied all the clues that can be found so far, and put forward various theories to explain this extinction phenomenon. But so far, there is still no 100% correct answer about the cause of this extinction.
Perhaps, such an answer is waiting for you to find.
Below, we will introduce some theories and theories about the reasons of dinosaur extinction, that is, introduce some basic background knowledge to you, and hope to provide some inspiration for you to find a better explanation.
Asteroid impact theory
1980, at a scientific seminar, American geologist Alvarez and others vividly preached a thrilling story that happened 65 million years ago according to their research results: on a sunny afternoon, in the tropical bush under the scorching sun, many different kinds and shapes of dinosaurs walked quietly by the lake or foraged in the water as usual; On the edge of the forest, a newly hatched hadrosaur is pacing back and forth around the egg nest; In an open field, a Tyrannosaurus rex is preparing to pounce on a giant triceratops. ...
Suddenly, a loud noise that I had never heard before broke the quiet world. A meteor with a diameter of several kilometers hit the earth. The collision was terrible, equivalent to the explosion of tens of thousands of atomic bombs in an instant. This is an unexpected asteroid. After colliding with the earth, the impact force can reach 10 15 tons of TNT explosive. A huge mushroom cloud with dust rose rapidly, soared into the sky, then dispersed, and finally enveloped the whole earth. Soon, dinosaurs could not see each other, because dark clouds covered the sky and there was no sunshine during the day. This terrible situation lasted for a year or two. The photosynthesis of plants was interrupted, so a large number of plants withered and died. Vegetarian dinosaurs who ate plants died one after another. Later, carnivorous dinosaurs also became extinct because they lost food.
This story is the essence of the theory that an asteroid hit the earth and led to the extinction of dinosaurs. Later, it was continuously supported by many scientists. Some scientists even believe that during this period, the earth not only experienced a large planetary impact, but also suffered many smaller but still life-threatening asteroid impacts, among which the traces of planetary impacts found in the Caribbean and Iowa in the United States can be confirmed.
The evidence of this hypothesis also comes from an amino acid found in sediments around the world 65 million years ago. This amino acid contains a lot of iridium, which is abundant in some celestial bodies, but it should not exist on the earth at all. This iridium-rich layer has been found in many areas of North America, Europe and Australia, and it was also found in Gamba, Tibet a few years ago.
Some scientists think that the explosion wiped out all dinosaurs. However, some scientists believe that only 70% of dinosaurs were extinct at that time, and other dinosaur species narrowly escaped this disaster, but gradually became extinct in the following millions of years. The latter statement is not unreasonable, because some dinosaur bones were still found in the strata formed after this incident 65 million years ago. For example, dinosaur remains were found in the upper and lower layers of New Mexico 60 million years ago. Fossils of Triceratops were also found in Cenozoic tundra in Alaska. These phenomena seem to indicate that some dinosaurs still struggled for millions of years after the big bang caused by the impact of asteroids on the earth, and eventually died out because they did not adapt to the new climate and environment.
The latest theory-large-scale submarine volcanic eruption
Antonio Qiqi, a famous Italian physicist, recently suggested that the extinction of dinosaurs was probably caused by a large-scale submarine volcanic eruption.
Professor Qiqi believes that at the end of Cretaceous, a series of large-scale volcanic eruptions occurred on the earth under the ocean, which affected the thermal balance of seawater, and then caused the change of land climate, thus affecting the survival of dinosaurs and other animals that needed a lot of food to survive. His reason is that the impact of modern submarine volcanic eruption on the ocean and atmosphere is well known, but its impact is far less than that of submarine volcanic eruption 65 million years ago.