What kind of world is the earth after the extinction of dinosaurs?

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 textual 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 views on dinosaur extinction are as follows:

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 the intake 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.

On our earth, there used to be many biological species 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 speculation. At the end of the Cretaceous period 65 million years ago, scientists have been arguing about what caused the death of dinosaurs and a large number of other creatures. Some people say that there was a geological orogeny on the earth at that time, because there were many mountains on the flat land, so the swamp was reduced and the climate became less humid and warm. The dinosaur's respiratory organs could not adapt to the dry, cold and dry air. In winter, the dinosaur ran out of food, so it came to a dead end. Some people say that the supernova explosion caused a strong change in the earth's climate, 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 have a long life span, they have destroyed the ozone layer of the earth and caused a devastating climate. Some people even say that it is the result of aliens coming to the earth to hunt, because they think dinosaur meat is particularly delicious. The evidence is that the dinosaur bones they found in the North Pole were marked by laser cutting. In short, it is really varied and strange. But the meteorite impact theory is generally recognized.

1980, American scientists found a high concentration of iridium in the stratum 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 associate it with the extinction of dinosaurs. According to the content of iridium, it is also inferred that the impact object is an asteroid with a diameter of 10 km. The impact of such a large meteorite on the earth is absolutely unparalleled. 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 10 years to finally get the preliminary results. They found this crater in the stratum of Yucatan Peninsula in Central America. It is estimated that the diameter of this pit is between 180 km and 300 km. Now, scientists are still doing further research on this pit.

Scientists began to paint us a heroic picture 65 million years ago. One day, dinosaurs were still eating and drinking carefree in paradise on earth. Suddenly, a dazzling white light appeared in the sky, and a boulder with a diameter of 10 km equivalent to the size of a medium-sized city fell from the sky. It was an asteroid, which fell into the sea at a speed of 40 kilometers per second and fell into a huge pit on the bottom of the sea. Seawater is rapidly gasified, and steam is sprayed into the sky for tens of thousands of meters. Then the tsunami was as high as 5 kilometers, spreading at an extremely fast speed, and the turbulent sea water swept everything in the landing area. After the turbulent waves swept the earth's surface, they met at the back end of the impact point. The huge seawater power triggered a strong volcanic eruption on the Deccan Plateau here, and the movement direction of the earth plates occurred at the same time.

What a terrible disaster this is. Meteorites hit the earth and produced a lot of dust, polar snow melted, plants were destroyed and volcanic ash filled the sky. For a time, the sky was dark, the temperature plummeted, and the dinosaurs were swept away and buried by heavy rains, flash floods and mudslides. 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 the year round, and the vast land is silent for a while. Thus an era in the history of biology ended.