Chinanews.com client, Beijing, July 3 (Reporter Shangguanyun) The large size and fast movements... This may be the first impression of dinosaurs in the minds of many people. They were once "overlords of the earth", but suddenly disappeared 66 million years ago.

　　A few days ago, "studies said that the asteroid impact on the earth is the main reason for the extinction of dinosaurs". Fang Linhao, associate professor of the School of Earth Sciences at China University of Petroleum (Beijing), gave an opinion on the extinction of "non-bird dinosaurs" in the late Cretaceous period in an interview with a reporter from China News.

Data Map: Tourists in Zigong Dinosaur Museum in Sichuan are woven. The museum is famous for its many burial sites of dinosaur fossils, huge number, large variety, well-preserved and continuous sequence. Photo by Liu Zhongjun

Asteroid impact destroying dinosaur habitat?

　　Why do dinosaurs become extinct? This is the question of many people. A few days ago, some media reported that a new study published on June 29 found that the extinction of dinosaurs was due to an asteroid impacting the earth, not a volcanic eruption.

　　The study believes that at the end of the Cretaceous era 66 million years ago, an asteroid hit Earth on the coast of Mexico today. The particles and gas released during the impact block the sun's rays for decades, resulting in continued winter. This study also showed the destructive impact of asteroid impact on the dinosaur habitat through modeling analysis.

　　The news quickly appeared on the hot search. Fang Linhao said that the academic view that the asteroid impacted the earth caused the extinction of dinosaurs was first inferred by American scientist Walter Alvarez in 1980, based on the clay layer in the stratum at the end of the Cretaceous period, mainly from extraterrestrial. "Iridium" is abnormal.

　　He introduced that the impact of the asteroid on the Earth caused the eruption of a super large volcano on the Deccan Plateau of India, which triggered a series of chain reactions that led to dramatic changes in the Earth’s climate. Non-bird dinosaurs could not adapt and eventually went extinct.

How terrible is this "intimate contact"?

　　If the asteroid and the Earth really come into an "intimate contact", it is indeed possible to bring a lot of disasters.

　　Astronomically defined, orbits are within the range of 1.3 astronomical units from the sun (1 astronomical unit is the average distance between the sun and the earth, about 150 million kilometers), and the celestial bodies with a distance of less than 0.3 astronomical units from the earth's orbit are near-Earth objects, which are near-Earth objects Collection of asteroids and near-Earth comets.

Data Picture: The picture shows the effect of NASA's asteroid passing by the earth.

　　Among them, a potential impact threatening celestial body with a diameter greater than 140 meters and a minimum distance from the earth's orbit within 0.05 astronomical units poses a direct threat to the earth.

　　Asteroids with larger diameters can easily cause disaster if they hit the earth. According to media reports, on February 15, 2013, an asteroid about 20 meters in diameter exploded over Chelyabinsk, Russia, indirectly injuring more than 3,000 buildings and injuring more than 1,600 people.

　　It is not far away that humans have successfully warned of an asteroid hitting the earth. On New Year's Day in 2014, scientists discovered that an asteroid will crash into Earth after 24 hours. This asteroid is very small and poses no threat to humanity.

Speculations and hypotheses in the legend

　　There have always been different opinions about the causes of the extinction of dinosaurs. In addition to the "asteroid impact theory", the term "volcanic eruption" was also quite popular.

　　The main content of the latter is that large-scale eruptions of volcanoes bring a large amount of toxic gases underground, and sulfur dioxide gas among them will also form acid rain that lasts for more than decades.

Data map: On July 11, 2019, the Guangdong Provincial Museum, the dinosaur skeleton attracted children's attention. China News Agency reporter Chen Jimin

　　In addition, after a large amount of volcanic ash floats to the stratosphere in the atmosphere, it will not be able to disperse for several months, forming a strong "sun umbrella" effect, plants can not carry out photosynthesis, and the surface temperature drops rapidly in a short period of time... resulting in severe cold weather, etc. as a result of.

　　Plants are gradually withering away, which causes the herbivorous dinosaurs that feed on them to fail to get enough food and gradually become extinct; the carnivorous dinosaurs also slowly die because there is no herbivorous dinosaurs as prey.

　　"In addition to the reasons mentioned above for the extinction of dinosaurs, there are geomagnetic reversal theory, dinosaur poisoning theory, etc. These are the historical facts of geohistory that occurred simultaneously with the "dinosaur extinction". They comprehensively act on the organic system of the earth. Any one is a blind figure." Fang Linhao explained.

　　However, some experts pointed out that dinosaurs did not disappear suddenly overnight, but there was a process, maybe even tens of thousands of years, but compared with the 180 million years that dinosaurs existed, tens of thousands of years were not To one thousandth.

They may not be completely extinct

　　In addition, Fang Linhao introduced that the scientific paper on June 29 mentioned above was titled "Asteroid Impact, Not Super Volcano Eruption, Leading to the Extinction of Dinosaurs at the End of the Cretaceous Period." The extinction of dinosaurs.

　　He said that according to the "Scientific Taxonomy" standard for classifying organisms, dinosaurs were not completely extinct, but some of them have evolved into today's birds. For example, in the late Jurassic and Cretaceous, some dinosaurs and birds have a relatively close relationship, with smaller bodies and feathers.

　　According to reports, a fossil specimen of the "Jurong Rainbow Dragon" was discovered earlier. It belongs to the near-bird dragon class of "Hirsch's near-bird dragon", and the asymmetrical blades on both sides of its tail feather axis indicate that it had auxiliary flight characteristics at that time.

　　"There are many types of dinosaurs, and the branches that have evolved into birds are not large. Many body types are the size of magpies today." Fang Linhao said that according to fossils and other evidence, birds in today's sense did not appear after the extinction of dinosaurs. .

Data Map: On December 8, 2016 local time, scientists from China, Canada and other countries discovered dinosaurs in amber for the first time in history. The first dinosaur specimen found in Amber was a hairy tail approximately 3.85 cm long. Based on the size of similar dinosaurs, the researchers concluded that this dinosaur is 18.5 cm long.

　　He said that it was precisely after the dinosaurs became extinct, that there was an environment where species vacancies appeared in the ecosystem on the earth-that is, the vacant niche, under which circumstances birds gradually flourished.

　　At the same time, originally in the dinosaur era, the weak mammals, with their tenacious vitality and the advantage of being a thermostat's body temperature regulator, also escaped huge disasters and obtained the opportunity to occupy the niche and have reproduced to this day. (Finish)