Hypotheses about the causes of dinosaur extinction

Hypotheses about the causes of dinosaur extinction

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It has long been known: dinosaurs became extinct at the end of the Cretaceous from the fall of an asteroid on Earth. There is such a version. However, there is little evidence. Scientists are still reasoning over the causes of extinction of the Lizards and are building new hypotheses.

Asteroid

This is one of the most popular scientific theories. She was nominated by the American physicist Luis Alvarez in 1980. It is believed that 66 million years ago a huge asteroid fell to Earth. The crash site is considered Chicxulub crater on the Yucatan Peninsula in Mexico. The celestial body raised clouds of dust into the atmosphere, awakened dormant volcanoes, which caused astroid winter and led to the extinction of dinosaurs and some other animals. Opponents of the theory believe that the crater is too small, there are craters on Earth and from more impressive celestial bodies (for example, Chesapeake or Popigaysky), moreover, at the time when they fell, no major changes in fauna occurred on Earth. Proponents of the theory parry this with the fact that reptiles became extinct as a result of several asteroids falling at once.After all, the death of dinosaurs occurred rather slowly over hundreds of thousands of years.

Active volcanism

Another hypothesis of extinction of dinosaurs - a significant increase in the volcanic activity of the Earth. Most often, scientists refer to the Deccan trap plateau, which is located in India and is covered with two-kilometer eruptive basalt. Its age is defined as 60 - 68 million years. Proponents of the theory of volcanism believe that volcanic activity lasted so long that the climate on Earth became colder and the dinosaurs froze. Opponents of the theory assure opponents that during a prolonged eruption dinosaurs could adapt to the cooling, as crocodiles did, and survive.

Changing of the climate

This hypothesis tells that dinosaurs died due to the Earth’s climate change caused by continental drift. Drift caused temperature fluctuations, the massive death of plants, changes in the food supply of lizards, the drying up of water bodies. There is also an assumption that due to changes in temperature in dinosaurs, only females or males began to hatch from eggs. This happened exactly the same as in modern crocodiles. And this led to the death of the species.There is a theory that during a cold snap, the shell of dinosaur eggs became thicker or thinner than was necessary. In the first case, the formed young could not leave the shell and die, and in the second - became a victim of predators or infections. This theory is opposed by studies by climatologists, who have already found out that there were no particular climate changes 66, 5 million years ago on Earth. The nearest severe cooling began at the end of the Eocene, that is, only 58 million years ago. Agree, a significant difference.

Changing atmosphere

This theory is connected with the fact that as a result of the cataclysms the atmosphere of the Earth changed its composition so much that the huge lizards could not breathe and they died. Scientists cite various reasons for this turn of events. Some still claim that the asteroids are to blame, others point to volcanoes. The fact is that during the heyday of dinosaurs, the oxygen content in the atmosphere was 10-15%, and the carbon dioxide content was only a few percent. Changes in the composition of the air led to a change in plants, and made it possible to develop a new fauna.Opponents of this hypothesis studied the composition of air of the ancient atmosphere of the Earth by rocks and deposits and concluded that the composition of air in the Cretaceous did not change significantly. At the end of the Cretaceous, the carbon dioxide content was about the same as 100 million years before, in the middle of the Jurassic period.

Appearance of flowering plants

This theory is associated with changes in the food supply of herbivorous dinosaurs. It is believed that it was during this period that the Earth’s vegetation began to change rapidly. There are new flowering plants for dinosaurs. Lizards could not adapt to the alkaloids that they contained, ate a new type of vegetation, were poisoned and died. As a result of the mass death of herbivores, predators have also become extinct.

Theory of Competition with Mammals

According to this theory, huge, unwieldy dinosaurs could not compete with small, mobile warm-blooded mammals, which also fed on their eggs. Some originals put forward an even more exotic version of the controlled evolution. This hypothesis is purely empirical. It consists in the fact that the whole Earth is a platform for a certain Supermind that intervenes in evolutionary processes precisely when they need to be directed along one or another channel.Periods of non-intervention can be tens of millions of years. In fact, dinosaurs could have owned the Earth for many more hundreds of millions of years, but it was time to give in to the nascent mammals, and they were simply swept away from the chessboard of life.

Coincidence of factors

The modern science is dominated by the theory of “great extinction,” according to which the appearance of flowering plants and climate change caused by continental drift became the main factors responsible for the death of the dinosaurs. At first, new plants displaced ferns and horsetails, because of the development of the flowering root system, the erosion of land decreased, and the flow of nutrients into the ocean slowed down. This led to the death of algae, from which extinct sea dinosaurs. Meanwhile, on land, animals adapted to new plants. The first mammals appeared. They ate eggs and cubs of dinosaurs. Due to the drift of the continents there was a change in air and sea currents, it became colder on Earth. First, the appearance of new dinosaur species ceased. Existing species existed for some time and then became extinct. Together with dinosaurs, mollusks died - ammonites and belemnites and many small algae. A total of 16% of the families of marine animals, 47% of the marine fauna and 18% of the families of land vertebrates disappeared.Snakes, turtles, lizards and crocodiles survived. Ammonites relatives survived - nautilus, corals and birds survived. The evolving mammals did not immediately capture the land they had inherited.

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  • Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

    Hypotheses about the causes of dinosaur extinction

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