The scientific community generally believes that about 65 million years ago, an asteroid with a diameter of 10 km hit the earth, and the energy released by the impact triggered a global fire, which heated the atmosphere to a very high temperature and burned most of the forests on the earth to ashes in a short time.
When an asteroid hits the earth, the huge energy generated by its explosion will raise a lot of dust. At the same time, the asteroid impact intensified the geological movement on the earth and led to some volcanic eruptions on the earth, causing a large number of volcanic ash to spray into the atmosphere. These tiny dust covered the sky and lasted all day, blocking the heat from the sun, causing the temperature of the earth's surface to drop rapidly.
Such a climate of ice and fire led to the extinction of dinosaurs on earth in a short time. According to scientists' estimates, more than 93% of mammals and most other species were also extinct in this event. Fortunately, some smaller and more adaptable mammals survived, making the seeds of life continue.
What caused the extinction of dinosaurs has always been the most concerned natural unsolved mystery.
Through the continuous exploration and exploration of scientists, asteroid impact has become the greatest possibility of dinosaur extinction. The famous American physicist Luis Alvarez and his son Alvarez, who first put forward this theory, won the Nobel Prize in physics.
Alvarez and his son noticed the abnormal enrichment of iridium when studying the strata at the junction of Cretaceous and Paleogene. This element is not common on earth, but it is abundant in meteorites, asteroids and other extraterrestrial bodies. Therefore, in the 1970s, they put forward the asteroid impact theory, also known as the "Alvarez hypothesis".
Since the asteroid impact led to the Cretaceous-Paleogene extinction and the dinosaurs became extinct, where did the asteroid impact? There must be a crater left, right?
195 1 year, Mexican oil company dug several wells in Yucatan Peninsula on the south coast of the Gulf of Mexico to study the stratum. One of the wells found andesite at1300m. This kind of rock is formed under high temperature and pressure, usually seen in volcanic eruption or meteorite impact. In the later exploration, the oil company found a huge arc structure extending from Yucatan Peninsula to the north and deep into the Gulf of Mexico. This structure is inconsistent with the surrounding geological structure, much like a crater.
After the 1990s, American scientists confirmed that the arc structure on Yucatan Peninsula was a crater with a diameter of at least180km, and the impact center was near the village of Chicxulub, so this crater was named Chicxulub Crater. Chicxulub crater was left after the impact of an asteroid that led to the extinction of dinosaurs, and its age is consistent with the Cretaceous-Paleogene extinction event.
Scientists estimate that the diameter of the asteroid that caused chicxulub crater is 10 km, and the energy generated during the impact is as high as 4.0, 10.23 Joule, which is about equal to the explosive power of10 billion tons of TNT. If you use the atomic bomb dropped by the US military in Hiroshima, its impact is equivalent to 7 billion atomic bombs.
The impact of asteroids has brought a series of geological disasters, including earthquakes, volcanic eruptions, tsunamis and impacts. The dust generated by the impact enters the atmosphere, wrapping the earth and isolating the light and heat of the sun. Under the combined action of various disasters, more than three-quarters of species on the earth have disappeared, including dinosaurs. The Mesozoic ended and the Cenozoic began.
Finally, correct some common misunderstandings:
First of all, the Cretaceous-Paleogene extinction occurred 66 million years ago, not 65 million years ago. In 2008, scientists at the University of California, Berkeley used argon-argon dating to determine that the mass extinction occurred 65.95 million years ago and fluctuated for 40,000 years, so the end time of the Cretaceous was updated to 66 million years ago.
Second, dinosaurs did not go extinct. Today's birds are descendants of dinosaurs, so now the Cretaceous-Paleogene dinosaur extinction event is called non-bird dinosaur extinction.
65 million years ago, the asteroid impact point was basically determined, located in the Yutanka Peninsula near Mexico. This crater can still be observed by remote sensing satellites today, reaching 200 kilometers directly, which is enough to show how powerful its impact energy is.
Large animals that can be within hundreds of kilometers will all perish in a short time after the impact, and the impact will spread to the whole earth, leading to the arrival of nuclear winter. A lot of dust blocked the atmosphere, which made plants unable to get enough sunlight. Sunplants in the world began to die, so herbivores could not survive, and finally carnivores could not survive.
Dinosaurs, as large creatures, died out the fastest. The Yutanka Peninsula was almost destroyed and turned into a straight pit of hundreds of kilometers, which triggered a powerful tsunami sweeping the world.
The impact also changed the life pattern on the earth. All the large creatures died, but only the smaller ones survived, which also gave the monkey room to live, and later evolved into today's human beings.
Ask experts and professors.
At first, people didn't know what caused the extinction of dinosaurs. Just a lot of speculation. It was not until the discovery of chicxulub crater that it was confirmed that the extinction of dinosaurs was directly related to the impact of asteroids on the earth.
When an asteroid big enough hits the earth, it will release huge energy. At the same time, the asteroid will completely disintegrate, splash into the sky during the violent impact, and then fall all over the world. The size of the impact area is directly related to the size of the asteroid. If the asteroid is big enough, dust and its own debris will splash far away and even cover the whole world.
In 1980s, physicist Luis á lvarez and his son geologist Walter á lvarez discovered that the iridium content in Cretaceous and Paleogene alternate strata was much higher than other strata. As we all know, iridium is a heavy metal element. In the early days of the earth's formation, all these heavy elements sank into the core, and the content in the crust was extremely low. However, the content of iridium in the strata alternating between Cretaceous and Paleogene is very high, which has attracted their attention.
It is found that the content of iridium in extraterrestrial objects is very high, so this situation points to a result: it is iridium brought by the impact of extraterrestrial objects on the surface. When an extraterrestrial body hits the earth's surface, a large amount of dust and its own debris are splashed into the sky and fall in all directions. The dust produced by this impact covered the earth, and in the long process of dust settlement, it brought rich iridium to the surface below. The data detected in various places fully confirmed this view, and the abnormal increase of iridium content was found in the strata alternating between Cretaceous and Paleogene all over the world.
Since the earth was hit by an alien object during that time, the next step is to determine the location of the impact:
As early as 195 1 year, an oil company discovered rocks formed by high temperature and high pressure when exploring oil in Yucatan Peninsula, Mexico. At first, this situation did not attract their attention. They just think it's a volcanic cone structure. Later, the oil company drilled such strange rocks in two other oil wells here, and more evidence showed that it had been hit by meteorites.
Later, according to the data drawn by satellite, it can be clearly seen that there is a huge crater on this peninsula, half of which is on land and half of which has been submerged in the ocean. The average diameter of this huge crater is 180 km. After determination, the data of this crater is similar to that of computer simulation, and the impact time is also consistent, so the location of the crater is determined.
We can imagine that one day 65 million years ago, without any warning, an asteroid with a diameter of more than 10 km hit the Yucatan Peninsula in Mexico today, releasing the energy equivalent to 100000000000000 tons of TNT explosive, equivalent to two million nuclear bombs exploding at the same time, splashing dust all over the world, killing a large number of plants, and causing global forests. Because the stratum at the impact site is rich in sulfur, the sulfur dioxide produced during the impact has brought fatal acid rain to most parts of the world. It took millions of years for the earth to repair the damage to the earth's ecology caused by this impact.
Text/Science Wharf
Remember the extinction of dinosaurs? Dinosaurs were creatures that lived on the earth before human beings appeared, but unfortunately, they have been extinct for about 65 million years now. There have been different opinions about why dinosaurs suddenly died out 65 million years ago, and the most recognized one is the asteroid collision theory.
It is said that an asteroid with a diameter of 7 to 65,438+00 kilometers and a weight of about 65,438+0.3 trillion tons fell to the earth, which caused environmental upheaval and led to the extinction of dinosaurs.
Let's imagine that one night 65 million years ago, you stood somewhere in North America and looked up at the sky. You would see something like a star. When you stare at it for an hour or two, you will find that the star is getting brighter and brighter. In fact, it is not an ordinary star, but an asteroid flying to the earth at a speed of 72,000 kilometers per hour. After 60 hours, the asteroid exploded in the atmosphere.
According to the iridium content in the clay layer, scientists speculate that the diameter of the object hitting the earth is about 10 km. What is this concept?
For example, if the intensity of the earthquake is changed, it will reach about 10 Richter scale!
It was not until 199 1 year later that geologists found the location where the impact occurred-it was located on the Yucatan Peninsula in North America and Mexico, which directly smashed a "big pit" for Mexico. It is understood that the diameter of this pit is between 180~300 kilometers, and later this pit was filled with seawater, so this place is what it is now.
Due to the impact of the asteroid ring, the Pacific Rim fault zone and Tethys tectonic domain were formed, and a large number of Mesozoic creatures became extinct!
The survivors of dinosaurs spent their disaster on the large-scale biological corpses in the Pacific Ocean, becoming today's "animal world".
65 million years ago, an asteroid hit the earth, leading to the extinction of dinosaurs. Where is the impact point?
Humans discovered the fossils of this prehistoric creature thousands of years ago, but they didn't know the significance of these stones at that time, and even used them as Chinese herbal medicines. The ancients thought it was a legendary keel, so they described it as a dragon! In ancient Central Asia, Xu Xi Anren described the protoceratops fossils found there as a lion's body, big claws and an eagle's head guarding gold, which became the most primitive source of the Griffin!
Dinosaur dusk
The discovery of the first dinosaur fossil
1676, a bone fossil was unearthed near Oxford, England. Prout determined that it was the lowest femur of a large animal, and it did not belong to any known creature. It was named Ban Long! 1699, Edward Luyde found a tooth fossil in the suburb of Oxford, which was later identified as a sauropod dinosaur fossil.
Dinosaur tooth fossils
The first complete dinosaur fossil
From 65438 to 0858, William Parker Fogg, a fossil collector, dug up an almost complete hadrosaur fossil in a mud pit in Hardenfield, New Jersey, indicating that this dinosaur was a biped. Previously, some dinosaur fossils had suspected that it was a biped, but this time the complete fossil was a real hammer!
Duck-billed dinosaur fossils
Since then, Osnier Charles Marsh and Edward Dwek Kopp have started a decades-long dinosaur fossil discovery war, which is called the fossil war. Their excavation was very violent and even used explosives, which destroyed many valuable dinosaur fossils, but they also made great contributions. Two bosses discovered 142 new dinosaur species!
Since the 20th century, dinosaur fossils have been found all over the world, even in Antarctica, which shows that these animals once spread all over the world a long time ago. According to comprehensive dating methods such as stratigraphic dating and isotope K40 dating, these animals were found in various strata before the Cretaceous, but suddenly disappeared after the late Cretaceous! This means that dinosaurs suffered unimaginable disasters during this period and suddenly became extinct! What kind of disaster is it? Paleontologists have been trying to find out why!
Chicxulub crater's discovery
195 1 Mexican petroleum formula A strange andesite layer was discovered during exploration in Yucatan Peninsula. There is only one reason, such as volcanic eruption, but no ancient volcano was found in the Gulf of Mexico! 1978, when Glenn penfield, a geologist hired by Mexican oil company, was investigating the geomagnetic anomaly maps of Yucatan Peninsula and Gulf of Mexico obtained by geological exploration planes, he found an almost complete circular structure, which was located in the Gulf of Mexico, and the other half was located in Yucatan Peninsula, with the edge near Chicxulub!
1980, several geologists suggested that the reason for the extinction of dinosaurs may be that an asteroid hit the earth during the transition period of Cretaceous and Tertiary. This hypothesis seems to be very telling, but there seems to be no impact crater, and external evidence is needed to support it! 198 1 Allen hildebrand, a researcher at the University of Arizona, also put forward a similar view and thought that the impact point might be near the Caribbean!
Allen hildebrand studied the sediments on the K-T border in Haiti, and found a large number of iridium, impacted Shi Ying and weathered materials similar to glass meteorites in the strata, and also found rock sediments possibly formed by tsunami, and found a large number of such strata near the Caribbean Sea! 1990, Allen hildebrand obtained the research data of Glenn penfield at that time, and also obtained the core of 195 1, so the evidence chain of the crater named after Hick Sulubo City gradually improved!
According to the size of the impact crater, experts speculate that the asteroid has a diameter of about 10 km, and the impact energy is as high as/kloc-0 10000000000000 tons of TNT, which is equivalent to about 2 million large Ivan hydrogen bombs (500000000000 tons of TNT equivalent) that have been exploded by human nuclear explosions.
The impact shock wave of asteroids completely destroyed the creatures within thousands of kilometers, causing a bigger tsunami. The splashing water will fall thousands of kilometers away to form an intercontinental fire, and then under the action of atmospheric circulation, 10 will float out smaller dust even in a few years! Moreover, the impact vibration will lead to frequent earthquakes and volcanoes, and a large amount of carbon dioxide will enter the atmosphere and become the decisive greenhouse gas that affects the climate! There are two theories, one is that dust will cause snow on the earth, and the other is that greenhouse gases will cause high temperature on the earth for thousands of years. However, in either case, dinosaurs, a large creature, are completely finished, and only all kinds of small-sized dinosaurs can survive.
Only chicxulub crater?
In the transitional period between Cretaceous and Tertiary, another super crater appeared. Relevant geologists believe that there is a huge geological structure of 400,600 kilometers at the bottom of the Indian Ocean near Mumbai, India. Due to geological movement, this structure has been somewhat deformed, but it can still be estimated that the asteroid that caused this structure at that time was as high as 40 kilometers in diameter!
The imaging of Shiva crater structure shows that red is the highest place.
Its influence also led to a series of subsequent volcanic eruptions. The basalt on Deccan Plateau can correspond to the geological age at that time, so the scale of basalt shows the scale of this super volcano, which is slightly smaller than that of Siberian Shield volcano, but the asteroid impact and volcanic eruption made dinosaurs extinct. Of course, some geologists think that this is just a super shield volcano structure, and there is no conclusion so far! But what is certain is that it must be an asteroid impact or volcanic eruption, or a volcanic eruption after an asteroid impact that led to the extinction of dinosaurs!
Dinosaurs must die because mammals want to live! We humans must thank that asteroid.
dinosaur
The evolution of life on earth has not been smooth sailing. Due to the change of natural geographical environment, mass extinction will occur. There have been two mass extinctions in the history of the earth. The first time was at the end of Paleozoic, when more than 60% of marine invertebrates were extinct, while all the primitive fish and ancient amphibians in vertebrates were extinct, and ferns declined obviously. The second time was at the end of Mesozoic, when more than 50% of invertebrates in the ocean were extinct except dinosaurs that ruled the earth. Dinosaurs lived in Triassic, Jurassic and Cretaceous in Mesozoic. After living on the earth for 65.438+0.6 billion years, dinosaurs suddenly became extinct about 65 million years ago. There are many speculations about the causes of dinosaur extinction, including asteroid impact theory, volcanic eruption theory and orogeny theory.
Among them, the asteroid impact theory is the most popular scientific view. In many places, scientists have found the anomaly of iridium content in the strata at the end of Mesozoic, which is about 30 times higher than the average value of adjacent rocks. This has become a strong evidence to support the hypothesis that asteroids hit the earth, because iridium is not common on the surface of the earth, but there is a high iridium phenomenon in asteroids or meteorites. Scientists speculate that an asteroid with a diameter of about 10 km hit the earth. In the northern coastal area of Yucatan Peninsula in North America, geologists discovered a crater named "Chicxulub Crater", which was partially submerged at the bottom of the sea.
chicxulub crater
The diameter of this crater is about 180 to 200 kilometers. The fractured rocks in the crater indicate that there was a violent explosion here, which is probably the impact point of the asteroid that led to the extinction of dinosaurs. When an asteroid hit the earth, some dinosaurs died directly in the impact. A large amount of dust generated by the impact blocked the solar radiation in the atmosphere for a long time, which led to the failure of photosynthesis of plants and the death of herbivorous dinosaurs and carnivorous dinosaurs due to lack of food sources. Recently, there was a movie called "Doomsday Escape", which told the story of a comet hitting the earth, which was very similar to the scene of the extinction of dinosaurs.
Extinction of the dinosaurs
An asteroid related to the dinosaur era hit Mexico, presumably an asteroid with a diameter of 20 kilometers, forming an impact crater with a diameter of 180 kilometers. The shock wave affected half the earth, at least equivalent to a nuclear bomb with a capacity of 1000 billion tons.
Under the violent collision, the kinetic energy of the asteroid is quickly converted into heat energy, which makes the asteroid and its surrounding environment quickly heat up and release to the surrounding areas, producing a huge shock wave, thus triggering an earthquake. Some volcanoes around erupted, and the shock wave swept half the earth, followed by a tsunami, which was also a global disaster and boiled the sea water, affecting almost the whole North American continent. Nevertheless, the impact of this asteroid did not directly lead to the death of all dinosaurs in the world. The extinction (or disappearance) of dinosaurs is more due to environmental changes caused by this disaster, or the extinction or evolution of some remaining dinosaurs.
Although it is difficult to trace the events 65 million years ago, such a large-scale violent impact will make a lot of dust enter the atmosphere to block sunlight, leading to a drop in temperature, and with the passage of time, the dust will gradually settle down. Due to the nature of dust emitted by asteroids or volcanoes, information can be obtained from some ice layers under the ground and ice sheets. The environmental information of 65 million years ago can be understood through drilling cores and ice cores. Information obtained from all over the world can prove that there was a "nuclear winter" on the earth 65 million years ago. The land temperature environment changed, some creatures could not adapt to the gradual extinction, and the plant species also changed, which led to the survival crisis of herbivores and eventually triggered a global extinction event.
This asteroid impact crater was discovered by a Mexican oil company in Yucatan Peninsula, and its widest point exceeds 180 km, so it is called Chicxulubo impact crater. The impact of asteroids and the extinction of a large number of species fully tell us that "no matter how high the martial arts are, we are afraid of kitchen knives", and Huahuachangzi has no resistance in the face of absolute power.
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