1. meteorite collision theory: 1980, American scientists found high concentration of iridium in the stratum 65 million years ago, which was dozens or even hundreds of times higher than the normal content. Such a high concentration of iridium can be found in meteorites, so scientists associate it with the extinction of dinosaurs. According to the content of iridium, it is also calculated that the impact object is an asteroid with a diameter of 10 km. It's too big. It's definitely an unparalleled blow. According to the earthquake intensity, it is about Richter scale 10, and the diameter of the crater produced by the impact will exceed 100 km. It took scientists 65,438+00 years and finally got the preliminary results. They found this crater in the stratum of Yucatan Peninsula in Central America. According to the calculation, the diameter of this crater is 65438+. Scientists are still doing further research on this big pit. _ _ _ Scientists began to describe the heroic scene 65 million years ago for us. One day, dinosaurs were still eating and drinking in paradise on earth, and suddenly a dazzling white light appeared in the sky. A boulder with a diameter of 10 km fell from the sky. It is an asteroid with a speed of 40 kilometers per second. The seabed was knocked out of a huge pit, and the seawater was rapidly gasified, and the steam was sprayed into the sky for tens of thousands of meters. Then the tsunami was as high as 5 kilometers and spread at an extremely fast speed. The turbulent sea swept everything that landed on land, and the turbulent waves swept the earth's surface, and then met at the back end of the impact point, where the huge sea power triggered a strong volcanic eruption on the Deccan Plateau. At the same time, it changed the movement direction of the earth's plates. What a terrible disaster this is. Meteorites hit the earth and produced overwhelming dust, polar snow melted, plants were destroyed and volcanic ash filled the sky. For a time, it was dark and the temperature plummeted. Heavy rain, flash floods and mudslides swept away the dinosaurs and buried them. In the next few months or even years, the sky is still full of dust and clouds, and the earth is buried all the year round. The vast land was silent for some time. Thus an era in the history of biology ended. Second, the orogeny said that the orogeny at the end of Cretaceous dried up the swamp, and many dinosaurs who made this their home could no longer survive. Because of climate change, plants have also changed, and herbivorous dinosaurs were unable to adapt to new foods and died out one after another. The herbivorous dinosaurs became extinct, and the carnivorous dinosaurs also lost their dependence. As a result, they also became extinct. This extinction process lasted1000-20 million years. By the end of Cretaceous, it was extinct on the earth. 3. Climate change theory: Due to plate movement, ocean currents have changed and the climate has changed greatly. The cold climate killed plants and dinosaurs died for lack of food. 4. Volcanic eruption theory: Due to volcanic eruption, a large amount of carbon dioxide is ejected, which impacts the global greenhouse effect and causes food death. Moreover, the volcano spewed fire, resulting in the release of a large amount of salt, the destruction of the ozone layer, harmful ultraviolet radiation on the surface, resulting in extinction. Antonio Cikic, a famous Italian physicist, recently suggested that the extinction of dinosaurs was probably caused by a large-scale submarine volcanic eruption. Professor Qi Jichi 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. Professor Qi Jichi believes that in the past, the scientific community knew very little about submarine volcanic eruption, and now it is necessary to conduct in-depth research on this phenomenon that seriously affects the earth's environment. For example, he said that Greenland once had dense vegetation, but when the global ocean water temperature balance changed, the cold ocean current changed direction and crossed Greenland, thus turning this big island into a land covered with snow and ice. This is a typical example that the change of ocean water temperature balance has a great influence on climate. Submarine volcanic activity is an important factor affecting the balance change of ocean water temperature. Therefore, Professor Zichichi believes that the change of ocean water temperature balance caused by large-scale eruption of submarine volcano should be taken as an important reference factor for studying dinosaur extinction. 5. Ocean ebb tide theory: According to Barker, when the ocean ebbs and when the land borders, creatures contact each other, which leads to the extinction of some species. Kangaroos, for example, can live in the island continent of Europe, but they will die if they meet other animals in South America. In addition to this relationship between eating and being eaten, there are also infectious problems such as diseases and parasites. 6. Warm-blooded animals say: Some people think that dinosaurs are warm-blooded animals, so they may not be able to resist the cold weather in the late Cretaceous and thus cannot survive. Because even if dinosaurs were warm-blooded, their body temperature was still not high, probably 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 physical 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. Seven. Man-eating theory: because of climate problems, flowers and plants are extinct in large numbers, so that herbivores gradually die, while carnivores become extinct because of lack of food. 8. Oppression theory: The rapid increase in the number of dinosaurs led to the extinction of herbivorous dinosaurs with limited plants, and then carnivorous dinosaurs that ate herbivorous dinosaurs died because of lack of food.