Prior to this, when studying chicxulub crater, scientists speculated that the crater was formed 65 million years ago, which coincided with the extinction time of dinosaurs. So paleontologists immediately exploded the pot, and they firmly believed that the reason for the extinction of dinosaurs was that meteorites hit the earth.
So the extinction of dinosaurs was really caused by a meteorite hitting the earth?
On our earth, there have been many biological species appearing and disappearing, which is an inevitable stage of biological evolution. But why did a large and dominant family like dinosaurs suddenly disappear from the earth? What happened to the earth 65 million years ago?
The reason for the extinction of dinosaurs has been debated in the scientific community. Some people think that it is caused by climate change, while others think that it is a struggle between species. There are various strange speculations, but what is recognized by most people is the impact of meteorites.
There is a layer of rocks in chicxulub crater called the K-T boundary by geologists, which is the boundary between Cretaceous and Tertiary. The lower rocks of this dividing line are rich in dinosaur fossils, but the dinosaurs in the upper rocks have disappeared, but the content of rare metal iridium is extremely high. In addition, people also found evidence of earthquake-stricken Shi Ying in rock formations, and only the violent impact of asteroids will produce such a mark as earthquake-stricken Shi Ying.
So scientists who firmly believe in the theory of meteorite impact painted such a picture: 65 million years ago, dinosaurs were eating and drinking carefree in the paradise on earth, and suddenly a dazzling white light appeared in the sky, and a boulder with a diameter of 10 km fell from the sky. It was an asteroid that 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 vaporizes rapidly, and steam is sprayed into the air for tens of thousands of meters. Then a tsunami as high as 5 kilometers was set off, which spread at an extremely fast speed. The flood swept everything on the landing site, the turbulent waves swept the earth's surface, and the mudslide swept away and buried a huge dinosaur family. The huge impact made the magma inside the earth active, many volcanoes erupted at the same time, volcanic ash filled the sky, and the earth instantly became purgatory.
In the next few months or even years, the sky was still dusty and covered with dark clouds, and the earth entered a low temperature because of the lack of sunshine all the year round, thus ending the dinosaur era.
However, the meteorite impact theory also has many loopholes.
First of all, asteroids are generally composed of elements such as silicon and iron. Even if such a huge asteroid falls on the surface of the earth for a long time, it is impossible to have no trace, but such a large meteorite has never been found on the earth.
Secondly, most of the rocks at the end of Cretaceous are igneous rocks formed by lava cooling, and the sedimentary rocks accumulated by dust only cover a small part of the surface. Then, can the dust raised by the asteroid impact bury most of the animals and plants on the earth in rocks several kilometers deep?
Furthermore, can iridium contained in asteroids spread evenly and even cover the whole earth's surface? Now that this element also exists in the depths of the earth, why only speculate that it comes from outside the earth rather than inside it?
Some people think that climate change led to the extinction of dinosaurs.
They believe that 65 million years ago, the climate on the earth suddenly changed, the temperature dropped sharply, and the earth was experiencing a long and cold winter. They also put forward a particularly interesting statement that dinosaurs were cold-blooded animals. They have no hair and warm organs. They can't adapt to the rapid drop of the earth's temperature, so they all freeze to death. However, this statement does not clearly point out the cause of climate change, and it is impossible to confirm whether the climate really changed 65 million years ago.
There is also a saying that species struggle.
These people think that at the end of the dinosaur era, the first small mammals appeared. These animals are all carnivores. At that time, only dinosaurs existed on the earth. These small carnivores eat dinosaur eggs. Due to the lack of natural enemies, the number increased rapidly for a time, dinosaur eggs were gradually eaten, and dinosaurs became extinct. However, through the study of dinosaur fossils that have been found, it is found that some small osteophytes in dinosaurs are enough to compete with early small mammals, so the "species struggle theory" is flawed.
The other is the theory of continental drift.
Geological research has proved that in the era when dinosaurs lived, there was only one continent on the earth called Pangea, and all dinosaurs lived on this continent. Due to the change of the earth's crust, this continent split and drifted greatly during the Jurassic period, and dinosaurs could not adapt to the climate environment of the New World and eventually became extinct. However, in modern geology, the "continental drift theory" itself is a hypothesis, and it is even more impossible to verify how dinosaurs became extinct.
The other is the theory of geomagnetic variation.
The magnetic field is very important to the earth, and its greatest function is to protect the earth. The magnetosphere formed by the earth's magnetic field can prevent electrons brought by the solar wind from directly acting on the earth, and can also block cosmic rays. Modern biology has proved that the death of some creatures is related to the magnetic field, and creatures sensitive to the magnetic field will lead to death when the earth's magnetic field changes. So these people think that 65 million years ago, the earth's magnetic field changed, and dinosaurs were very sensitive to magnetic fields, so they became extinct.
There is even more outrageous saying that plant poisoning is said.
They believe that at the end of the dinosaur era, angiosperms on the earth grew in large numbers, while gymnosperms that existed for a long time gradually became extinct. These newly grown angiosperms contain toxins that gymnosperms do not. Dinosaurs were huge, so they ate too much, and the toxins they ate accumulated too much in the body, so they were poisoned. But this statement only applies to herbivorous dinosaurs. How did the carnivorous dinosaurs become extinct? It obviously doesn't make sense.
According to the law of natural development, some people think that the extinction of dinosaurs was caused by the aging of species.
These people think that dinosaurs occupied the earth for more than 65.438+0.6 billion years, and their bodies were too large because of their unrestrained life, and their horns and other bones were also abnormally developed, which brought great inconvenience to life and eventually led to extinction. The basis is that the most representative confusing dragon among dinosaurs, with a body length of 25 meters and a weight of 30 tons, gradually lost its viability because of its huge size and slow movement. There is Triceratops, because it has three horns and an unusually developed skeleton to protect its head, but it has gone to the road of self-destruction.
But not all dinosaurs are so huge. There are small dinosaurs with a body length of only about one meter, and there are dinosaurs with bones like deer that can run briskly. But why did this dinosaur die out at the same time? So it is not credible to say that dinosaurs died out because of the aging of species.
At present, there is no conclusion about the cause of dinosaur extinction. Although there are various reasons, it can be seen that the general direction is that the climate and environment have changed. Whether it is meteorite impact, climate change or continental drift, it is nothing more than the change of the earth's environment caused by external factors. Dinosaurs could not adapt to this environment and eventually went extinct. Of course, meteorite impact is a destructive external factor and a more convincing inference.
This also gives us a revelation that we should take care of the earth's environment. Now the greenhouse effect is more and more serious, and the earth is more and more overwhelmed. Only by caring for the earth can we avoid repeating the same mistakes, and the primary performance of realizing long-term development is to protect the earth.