At a scientific conference in 1980, American geologist Alvarez and others, based on their research, vividly recounted a thrilling story that took place 65 million years ago: On a sunny afternoon, in a tropical shrubland under the blazing sun, many different kinds and forms of dinosaurs were calmly strolling along the lake or foraging in the water, just as they always did; at the edge of the forest, a hadrosaur that had just finished incubating its eggs was pacing back and forth near its nest; on an open field, a Tyrannosaurus Rex was preparing to pounce on a giant Triceratops…
Suddenly, an unprecedented roar shattered the tranquility of the world. A meteor several kilometers in diameter violently struck the Earth. The impact was devastating, equivalent to the explosion of tens of thousands of atomic bombs in an instant. This was an unexpected asteroid, and the impact force was equivalent to the explosion of 1015 tons of TNT. A massive mushroom cloud, billowing with dust, rapidly rose into the sky, then dispersed, eventually engulfing the entire Earth. Soon, the dinosaurs could no longer see each other, as the dark clouds blocked out the sun, and even daytime was devoid of sunlight. This terrifying situation lasted for one or two years. Plant photosynthesis was disrupted, causing massive withering and death. Herbivorous dinosaurs, which ate plants, perished as a result. Later, carnivorous dinosaurs also went extinct due to the loss of their food source.
This story is the essence of the theory that an asteroid impact caused the mass extinction of dinosaurs. It has since gained increasing support from many scientists. Some even believe that Earth not only experienced one major asteroid impact during this period, but also suffered numerous smaller but still life-threatening asteroid impacts, with evidence of such impacts found in the Caribbean Sea and Iowa, USA.
Evidence for this hypothesis also comes from an amino acid found in sediments dating back 65 million years around the world. This amino acid contains a large amount of iridium, an element abundant in certain celestial bodies but which should not exist on Earth. Iridium-rich strata have been discovered in many regions of North America, Europe, and Australia, and were also found a few years ago in the Gamba region of Tibet, my country.
Some scientists believe that the explosion wiped out all dinosaurs. However, others argue that only 70% of the dinosaurs perished at that time, while other species barely escaped the catastrophe but gradually became extinct over the following millions of years. This latter view is not without merit, as dinosaur skeletons have been found in strata formed after the event 65 million years ago. For example, dinosaur remains have been discovered in strata dating back approximately 60 million years in New Mexico, USA. Triceratops fossils have also been found in the Cenozoic permafrost of Alaska. These findings suggest that after the massive explosion caused by the asteroid impact, some dinosaurs struggled to survive for millions of years before finally succumbing to the new climate and environment and becoming extinct.
