There have been five mass extinctions on Earth, the most famous of which was 66 million years ago, which led to the disappearance of three-quarters of species including dinosaurs. Scientists have been exploring the causes of this extinction, and the strongest evidence is that an asteroid hit Mexico's Yucatan Peninsula, causing global climate change and an ecological crisis. However, there is still a lot of controversy and unsolved mystery about the specific details and impact of this impact.
According to scientists' estimates, 66 million years ago, an asteroid with a diameter of about 10 to 15 kilometers hit the Yucatan Peninsula at a speed of 20 kilometers per second, forming a huge crater 180 kilometers wide, releasing the energy equivalent of tens of billions of tons of TNT explosives, which is thousands of times the size of the global nuclear **. The impact produced huge shock waves, tsunamis, and volcanic eruptions that destroyed the surrounding life and environment. At the same time, a large number of rocks and debris were thrown into the air, forming a thick cloud of dust that obscured the sunlight and plunged the earth into darkness and cold.
The dust cloud after the impact includes not only rocks and debris, but also some elements and compounds in the impact and the earth's crust, such as silicates, sulfur, carbon, etc. The distribution and deposition of these substances in the atmosphere have important effects on the Earth's climate and organisms. Recently, some scientists have analyzed sediments and simulated climate and found that silicate dust may be a major factor in the extinction. The particle size of these dusts is 0Between 8 and 8 microns, it can stay in the stratosphere for 15 years, blocking most of the solar radiation and lowering the Earth's temperature by 25 degrees Celsius for nearly 20 years. Such temperatures were fatal for warm-blooded animals such as dinosaurs, and also affected the photosynthesis of plants, leading to the collapse of the food chain. In contrast, substances such as sulphur and soot may also have a cooling effect, but they remain in the atmosphere for a shorter period of about 8 years, so their impact may be overestimated.
The impact was devastating to life on Earth, especially for large land animals like dinosaurs. According to the fossil record, dinosaurs dominated the Earth before the Cretaceous-Paleogene border, but after the line, they almost disappeared, and only the bird branch survived. Scientists believe that the extinction of the dinosaurs may have been due to their sensitivity to temperature changes, as well as their high demand for food. When the earth was in the middle of winter, plants were dying, and food was scarce, dinosaurs struggled to sustain themselves. Birds, on the other hand, have a higher chance of survival because they are small in size, have a fast metabolism, and are able to adapt to different environments and foods. In addition to dinosaurs, other terrestrial animals, such as mammals, amphibians, reptiles, etc., were also affected by the impact, but their extinction degree and recovery rate varied, which may be related to their size, ecological niche, adaptability, and other factors. In the ocean, impacts have also caused a large number of extinctions, especially some plankton, corals, shellfish, etc., which are very sensitive to changes in temperature and light. Some fish, cetaceans, sharks, etc. have survived relatively well, which may be related to their range of activities, feeding habits, metabolism and other factors.
Scientists' research into this extinction event began in 1980, when some physicists and geologists discovered iridium anomalies in some deep-sea sediments, an element that is scarce in the Earth's crust but abundant in asteroids and meteorites. They speculate that the iridium is the result of an asteroid that hits Earth, brings it into the atmosphere, and then deposits it on the surface. They proposed the asteroid impact theory as the main cause of the Cretaceous-Paleogene mass extinction. Later, scientists discovered a huge crater in Mexico's Yucatan Peninsula, named Chicxulub Crater, whose age and size are consistent with the asteroid impact theory, providing strong evidence for this hypothesis. In addition, scientists have found other evidence of Cretaceous-Paleogene boundary sediments around the world, such as silicate chondrites, quartz cones, volcanic glass, etc., which are the products of impact events. Recently, scientists have also found evidence of post-impact biological and environmental changes, such as the death of fish and plants, sediment chaos, and the appearance of charcoal, at a fossil site in North Dakota, USA, reflecting the power and impact of the impact.
This extinction event was one of the most important events in Earth's history, changing life and the environment on Earth, providing opportunities for new species and evolution. At the same time, it also provides us with a warning that the Earth is a fragile system that can be threatened and disturbed from the outside, as well as by internal imbalances and destruction. Therefore, we should cherish and protect our homeland and avoid repeating the mistakes of dinosaurs.
In order to prevent the danger of asteroids hitting the Earth, scientists have established a number of monitoring and early warning systems, such as NASA's Near-Earth Object Observation Program (NEO), the European Space Agency's Near-Earth Object Coordination Center (NEOC), etc., which can track and analyze the orbits and characteristics of asteroids and comets in space, and detect and evaluate celestial objects that may threaten the Earth in time. At the same time, scientists are also exploring some possible defense and interception methods, such as the use of nuclear**, gravitational traction, kinetic impact, laser evaporation, etc., to change or destroy the asteroid's orbit and structure, causing it to deviate or disintegrate, and avoid collision with Earth.
However, asteroid impact is not the only crisis facing the earth, there are some internal problems, such as climate warming, environmental pollution, biodiversity loss, resource depletion, etc., these problems are caused by human activities and consumption, they will also cause serious impact and damage to the earth's life and environment, and even trigger new extinction events. Therefore, we should adopt a more sustainable and environmentally friendly way to reduce our burden and harm to the earth, maintain the balance and stability of the earth, and promote the development and progress of the earth.
In conclusion, the event of the extinction of the dinosaurs caused by the impact of an asteroid on Earth is a shocking and thought-provoking story that gives us an understanding of the Earth's past and future, as well as a reflection on the responsibility and mission of humanity. We should learn from this story to cherish our lives and the environment and protect our homes and futures.