the mystery of dinosaur extinction

dinosaur fossils

in the Mesozoic era, more than 2 million years ago, many 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 had enough food and gradually flourished, with more and more kinds. They have constantly differentiated into various kinds of reptiles, some of which have become turtles today, some have become crocodiles today, some have become snakes and lizards today, and some of them have evolved into mammals all over the world today. Dinosaurs are the largest class of all terrestrial reptiles, and 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 more than 1 million years, but for some reason, they suddenly became extinct in a short period of time 65 million years ago. Today, people only see a large number of dinosaur fossils left at that time.

Edit this hypothesis about the extinction of dinosaurs

Query and explanation about the extinction of dinosaurs

The last dynasty

On our earth, there were many kinds of creatures that appeared and then disappeared, which is an inevitable stage in the history of biological evolution. But why a huge and dominant family like dinosaurs suddenly disappeared from the earth can't help but arouse our speculations. At the end of the Cretaceous period 65 million years ago, scientists have been arguing about what happened that killed dinosaurs and a large number of other creatures. Some people say that the earth had a geological orogeny at that time, because many mountains grew on the flat land, so the swamp was reduced and the climate became less humid and warm. The respiratory organs of dinosaurs could not adapt to the dry, cold and dry air, and in winter, dinosaurs ran out of food, so they went to a dead end. Some say that the supernova explosion caused a strong change in the earth's climate, and the temperature suddenly rose and then dropped very low. Others say that dinosaurs ate a lot of flowering plants, and there were many toxins in these flowers. Dinosaurs ate a lot, so they died of poisoning. The evidence is that flowering plants began to appear at that time. Others ingeniously said that it was because dinosaurs, a huge animal, ate too much and kept farting, releasing a lot of methane gas into the air. Because they are too numerous and live for a long time, they destroy the ozone layer of the earth and cause a devastating climate. Some people even say that it was the result of aliens coming to the earth to hunt, because they thought dinosaur meat was particularly delicious. The evidence is that the dinosaur bones they found in the North Pole have traces of being cut by laser. Some scientists also believe that it is because of the decline of the sea surface that new land came out. Some dinosaurs had the habit of migrating and went to other places, which did not adapt to the environment there and eventually became extinct. In a word, it's really varied and wonders. However, the theory of meteorite impact is generally recognized by everyone. In 198, American scientists found high concentration of iridium in the strata 65 million years ago, and its content exceeded the normal content by dozens or even hundreds of times. This concentration of iridium can be found in meteorites, so scientists have linked it to the extinction of dinosaurs. According to the iridium content, it is also inferred that the impact object is an asteroid with a diameter of 1 kilometers. The impact of such a large meteorite on the earth is definitely an unparalleled blow. Calculated by the intensity of the earthquake, it is about 1 on the Richter scale, and the crater produced by the impact will be more than 1 kilometers in diameter. It took scientists 1 years to finally get the preliminary results. They found this big pit in the stratum of Yucatan Peninsula in Central America. It is estimated that the diameter of this pit is between 18 km and 3 km. Now, scientists are still doing further research on this pit. Scientists began to paint us the heroic scene 65 million years ago. One day, the dinosaurs were still eating and drinking carefree in the earth paradise. Suddenly, a dazzling white light appeared in the sky, and a boulder with a diameter of 1 kilometers equivalent to a medium-sized city fell from the sky. It was an asteroid, which crashed into the sea at a speed of 4 kilometers per second, and crashed into a huge deep pit at the bottom of the sea. 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 it spread at an extremely fast speed, and the raging water swept everything on the landing ground. After sweeping the surface of the earth, the surging waves met at the back end of the impact point, where the huge seawater power triggered a strong volcanic eruption on the Deccan Plateau and made the movement direction of the earth plate happen at the same time. What a terrible disaster it was. 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, the temperature plummeted, heavy rain, flash floods and mudslides swept the dinosaurs away and buried them. In the next few months or even years, the sky is still dusty and covered with dark clouds, and the earth enters a low temperature because it has not seen sunlight all year round, and the vast land is silent for a while. An era in the history of biology ended like this. Of course, there are more than these statements about the extinction of dinosaurs. The rest are examples:

Climate change theory

65 million years ago, the earth's climate suddenly changed, and the temperature dropped sharply, which caused the oxygen content in the atmosphere to drop, making dinosaurs unable to survive. Some people think that dinosaurs were cold-blooded animals, with no hair or warm organs, unable to adapt to the decline of the earth's temperature, and all of them were frozen to death.

the theory of species struggle

at the end of the dinosaur era, the first small mammals appeared. These animals were rodent carnivores and probably fed on dinosaur eggs. Due to the lack of natural enemies, more and more small animals eventually ate dinosaur eggs.

Continental drift theory

Geological research proves that there was only one continent of the earth in the age when dinosaurs lived, namely "Pangea". Due to the change of crust, the continent split and drifted in Jurassic, which eventually led to the change of environment and climate, and dinosaurs became extinct.

geomagnetic variation theory

Modern biology proves that the death of some creatures is related to the magnetic field. Creatures that are sensitive to the magnetic field may lead to extinction when the earth's magnetic field changes. It can be inferred that the extinction of dinosaurs may be related to the change of the earth's magnetic field.

Angiosperm Poisoning Theory

At the end of the dinosaur era, gymnosperms on the earth gradually died out and were replaced by a large number of angiosperms. These plants contained toxins that were not found in gymnosperms. The giant dinosaurs ate a lot, and their intake of angiosperms led to excessive accumulation of toxins in their bodies, and they were finally poisoned. Carnivores were poisoned after eating poisonous meat.

acid rain says

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

Meteorite Impact Theory

There is a Chicxulub Crater on Mexico's Yucatan Peninsula. What does it have to do with the extinction of dinosaurs 65 million years ago? The answer lies in this white rock. This layer of rock is called K-T boundary by geologists, which means the marker line of Cretaceous-Tertiary boundary. The lower rocks are rich in dinosaur fossils, but above the K-T boundary, dinosaurs disappeared. The K-T boundary rocks contain iridium, which is a rare metal with an average content of only one billion in the earth. However, the iridium content in this rock layer is 2 times higher than the normal content. Where else can I find so much iridium? In space. The iridium content in space is 1 times higher than that of the earth. People also found evidence of shocked quartz in this layer of white rock, and only asteroids would leave such marks. High concentrations of iridium and shocked quartz occur in tertiary boundary rocks in many parts of the earth. This global trace can only come from the most violent impact. The location of the impact is now Yucatan Peninsula in Mexico. The impact 65 million years ago was so violent that nothing in human history could compare with it. The asteroid or comet that hit the earth at that time was about 6 miles wide. It rushed to the surface of the earth at a speed of more than 4 times the speed of sound. It is so huge that when it hits the earth, its front end has already touched the ground, but its tail is still at an altitude of 35, feet, which is equivalent to the flying height of a jet airliner. What hit the earth was a huge rock the size of a mountain. There are many hypotheses about the reasons for the extinction of dinosaurs. However, these hypotheses have more supporters in the scientific community. Of course, there are imperfections in each of the above statements. 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 "species struggle theory". In modern geology, the "continental drift theory" itself is still a hypothesis. "Angiosperm poisoning theory" and "acid rain theory" also lack sufficient evidence. There are many doubts about explaining the increase of iridium content in rock strata and the extinction of dinosaurs by asteroid impact on the earth. 1. Asteroids are generally composed of silicon and iron elements, so it is impossible for such a huge asteroid to disappear even after a long period of time, and such a large meteorite has never been found on the earth; 2. At the end of Cretaceous, most of the 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 impact of an asteroid bury most of the animals and plants on the earth in the rock layers several kilometers deep? 3. Can the iridium contained in an asteroid spread evenly and cover the whole earth's surface? Iridium also exists in the depths of the earth. Why only speculate that iridium comes from outside the earth rather than from inside the earth? Therefore, the real reason for the extinction of dinosaurs needs further exploration.

orogeny theory

The orogeny that happened at the end of Cretaceous dried up the swamp, so many dinosaurs who lived in the swamp could no longer live. Because of climate change, plants also changed, and herbivorous dinosaurs could not adapt to new foods and died out one after another. The extinction of herbivorous dinosaurs made carnivorous dinosaurs lose their dependence and became extinct as a result. This extinction process lasted for 1 to 2 million years. By the end of Cretaceous, it was extinct on the earth.

Volcanic eruption theory

Volcanic eruption

Because of the volcanic eruption, a large amount of carbon dioxide is emitted, which causes the greenhouse effect of the earth to be violently excited and causes plants to die. Moreover, volcanic eruption releases a lot of salt, ruptures the ozone layer, and harmful ultraviolet rays irradiate the earth's surface, causing biological extinction. Antonio Zichichi, a famous Italian physicist, recently suggested that the cause of the extinction of dinosaurs was probably a large-scale submarine volcanic eruption. Professor Zichichi 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 much smaller than that of submarine volcanic eruption 65 million years ago. Professor Zichichi believes that in the past, the scientific community knew 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 used to grow dense vegetation, but when the global ocean water temperature balance changed, the cold ocean current changed direction and passed through 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 impact on the climate. Submarine volcanic activity is an important factor affecting the balance change of ocean water temperature. Therefore, Professor Zichichi thinks that the balance change of ocean water temperature caused by the large-scale eruption of submarine volcano should be regarded as an important reference factor to study the extinction of dinosaurs.

ocean ebb theory

according to Robert Barker, when the ocean ebb, when the land borders each other, the creatures touch or influence each other, which leads to the extinction of some species. Kangaroos, for example, can live on the island continent of Oceania, 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 also problems of infection and spread of diseases and parasites, and dinosaurs may become extinct.

Warm-blooded animals say

In the past, all scientists thought that dinosaurs were cold-blooded or warm-blooded animals like other reptiles, but with the increasing fossil data, people's understanding has also changed. Some people suggested that some dinosaurs might be warm-blooded animals. First of all, they think that some dinosaurs are extremely agile, and they don't crawl on the ground like snakes, but run on the ground with two hind legs, with a speed of 2 to 9 kilometers per hour. This requires a strong heart and a high metabolism, which is obviously impossible for cold-blooded animals. Secondly, dinosaurs ate a lot. It is speculated that a 3-ton sauropod dinosaur may eat nearly 2 tons of food every day, and only warm-blooded animals need so much energy. Judging from the fact that carnivorous dinosaurs are far less than herbivorous dinosaurs, this is also reasonable. In addition, there are some smaller dinosaurs, and their bodies are covered with a layer of feathers or hair, which is also to prevent the loss of body temperature. Other aspects, such as the study of bones, also preliminarily show that some dinosaurs were warm-blooded animals. As soon as the theory of warm-blooded dinosaurs was put forward, it was strongly criticized, but it is still difficult to draw a conclusion. Some people think that dinosaurs were warm-blooded animals, so they could not withstand the cold climate in the late Cretaceous and could not survive. Because even if dinosaurs are warm-blooded, their body temperature is still not high, which may be similar to that of living sloths, and to maintain such a body temperature, they can only live in tropical climates. At the same time, the respiratory organs of dinosaurs were not perfect, and they could not fully replenish oxygen. They did not have thick hair to avoid body temperature loss, but they easily lost 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 enter the cave to avoid the cold, so if the cold days last for a few days, they may be frozen to death because of exhaustion of physical strength. However, there is a doubt in this theory, that is, dinosaurs are not all so huge, and they may not all be able to hide in caves to take refuge, so this theory is not perfect.

The theory of cannibalism

cannibalism

Because of climate problems, a large number of plants are extinct, so that plant-eating herbivores gradually perish, while carnivores, because of lack of food, become crazy and self-defeating. Doubt: Since the extinction of plants led to the extinction of dinosaurs, why did omnivorous dinosaurs that ate insects and so on also become extinct, while other animals were safe and sound? )

oppression theory

The number of dinosaurs increased rapidly, which led to the extinction of herbivorous dinosaurs under the condition of limited plants, and then relied on eating grass.