The extinction of the dinosaurs could date back to 65 million years ago. At that time, not only various dinosaur that ruled the earth for over 100 million years were extinct, and the same tragic fate also fell to other living creatures living on the land, in the sea and on the sky. After this great catastrophe, about 50% of the biological creatures and almost 75% of the species on the earthe were disappeared forever since then.

    This was really a major extinction and catastrophe. The results of the extinction made the biological world on the earth had undergone fundamental changes around the time about 650 million years ago. This extinction marked the end of the Mesozoic, the earth's geological history entered a new era - the new generation.

Through unremitting efforts, scientists analyzed and studied all the clues that can be found and put forward all kinds of theories that explain the phenomenon of extinction. But so far, with regard to the reasons for this extinction, there was still not a 100% correct answer.

    Perhaps, the answer was waiting for you to find out.

一.Theory of Meteorite Collision:

    In 1980, scientists in the United States discovered high concentrations iridium in the stratum about 650 million years ago, and their contents were dozens or even hundreds of times more than normal content. This iridium in this concentration also could be found in meteorites, so scientists put it linking up with the extinction of dinosaurs

    Scientists have begun to describe for us the heroic scene 650 million years ago, one day, dinosaurs were still enjoying eating and drinking freely in paradise on earth, suddenly it appeared a white light in the sky, which was equivalent to the size of a medium-sized city. It was an asteroid, crashing into the sea with a speed of 40 kilometers, leaving a large pit in the sea, which was really a terrible disaster. Meteorite hit the earth generated overwhelming dust, snow in the polar melt, plant destroyed, the sky was full of ash. At that time, the earth was completely dark, temperatures plunged, heavy rains continued, flash floods continued, landslides swept away and buried up the dinosaurs. Over the next several months to several years, the sky was still filled with smoke and dust, thick black clouds were rolling, and the earth had not seen sunlight throughout years, then it entered the low temperature, the entire world was in a time of silence. An era of the biological history was ended.

二.Theory of Comet Collision:

    The theory of comet collision was begun by the view that extinction occurred every 260 million years that put forward by paleontologists - David Raup and John. Louis Alba Razvan gave this argument and his theory to astrophysics - Charlie myohla, later Myohla thought this is because of the gravity of the half satellite Nemesis star, which periodically put the comet into the Earth.

三.Theory of Orogeny:

    The orogeny occurred at the end of the Cretaceous, made swamp dried up, and many dinosaurs that took the swamps as home could not live again. After the change of the climate, plants had also changed, and herbivorous dinosaurs in nature could not adapt to new food and became extinct gradually. Herbivorous dinosaurs, carnivorous dinosaurs lost supports and extinct as a result. This extinction process lasted for 10 million to 20 million years. By the late Cretaceous, they finally disappeared on Earth

四.Theory of Climate Change:

    As the result of plate movements, ocean currents were changed and led to a huge climate change. Cold climate made plants dead, dinosaurs extinct because the lack of food.

五.Theory of Volcanic Eruptions

    Because of volcanic eruptions, a large amount of carbon dioxide emitted, the greenhouse effect was enhanced on the earth, making food dead. Moreover, the volcano released a large amount of salt elements, then the ozone layer was disruptive, harmful ultraviolet radiation illuminated the earth's surface, resulting in biological extinction.

六.Theory of Ocean Low Tide

    According to Barker's statement, when the ocean had low tide and the land bordered on with each other, a certain class of creature was extinct as a result. For example, kangaroo could live on European island, but when they came to South American continent and met other kinds of animals, they would die. In addition to this relationship between eating and being eaten, there are infectious problems such as diseases and parasites.

七.Theory of Warm-blooded animals:

    Some people thought that dinosaurs were warm-blooded animals, so they could not withstand the cold weather in the late Cretaceous period and could not survive. Warm-blooded animals were different from cold-blooded animals in one place, which was if the temperature dropped below a certain range, it was necessary for them to increase the consumption of energy to increase the body temperature, the body also became weak quickly. Due to the large body, they could not enter the cave for sheltering, so if the cold days lasted for a few days, perhaps they would have been freezing to death due to running out of energy.

八.Theory of Cannibalism

    Due to the climate problems, lots of flowers and plants died off, which led to the extinction of herbivorous dinosaurs gradually and those meat-eaters also died because of lack of food.

九.Theory of Oppression

    The number of dinosaurs increased sharply, but the plant was limited, resulting in the extinction of herbivorous dinosaurs, and then the carnivorous dinosaurs who relied on eating herbivorous dinosaurs also died because of lack of food.

十.Theory of Mammal criminals:

    In the latter half of the Mesozoic, the ancestors of mammals appeared. According to the record of fossils, the mammals was very small mammal in size, the numbers were very limited, until the late Cretaceous period, the number of mammals began to increase rapidly. It’s speculated that they belonged to omnivorous animals who took insects as staple food, when these small mammals discovered the dinosaur eggs, they continued taking and eating them.

十一.The Aging of Species:

    The boom period of dinosaurs lasted for more than one hundred million years, which made its body too huge. Moreover, the horn and other skeletal abnormalities were also too well developed, therefore, generated great inconvenience in life and eventually led to the extinction of dinosaurs.

十二.Theory of Alkaloids :

    According to this doctrine, the last period of the dinosaurs’ survival - the Cretaceous, flowering plants began to emerge, in which certain types had toxic alkaloids, due to a large number of ingestion, dinosaurs was poisoned and dead. Mammals could use taste and smell to distinguish poisonous plants, but the dinosaurs did not have this capability.

    In addition to the above-mentioned 12 kinds of claims, there were also "infectious disease", "radiation from the universe or a supernova explosion", "did not take on the Noah's Ark," "solar system shock theory" and other not well known theories. As for which one was the best argument, it depended on everyone's mind, there was no definite right and wrong, after all, the mystery of dinosaur extinction has not really solved.