The extinction of dinosaurs on Earth has long been the talk of scientists. This ancient animal group was declared extinct 66 million years ago. The physicist Luis Alvarez's hypothesis is the most prominent view explaining the extinction of the dinosaurs. Alvarez's hypothesis was published in the journal Science entitled Extraterrestrial Cause for the Cretaceous-Tertiary Extinction in 1980.
Quoting Britannica, Alvarez's hypothesis explains, about 66 years ago an asteroid hit Earth. This cataclysm caused the extinction of the dinosaurs. According to Alvarez, the main evidence for his hypothesis is related to the discovery of the Cretaceous-Paleogene layer containing high levels of iridium.
The layer is in the rock strata of the geochronological boundary zone between the Mesozoic and Neozoic eras, about 65.5 million years ago. The iridium-rich layer mostly covers the rock layers that contain dinosaur fossils.
According to Alvarez, the content of iridium is very rare in the Earth's crust. He argues, the content comes from outer space objects such as asteroids. Alvarez also concluded, from the discovery of the evidence, then 66 million years the asteroid hit Earth which resulted in the extinction of the dinosaurs.
At first the hypothesis was published causing controversy. However, it is gradually gaining support as an acceptable hypothesis to explain the sudden extinction of the dinosaurs. Evidence that supports one of them is the study of the ancient Chicxulub crater on the Yucatan Peninsula, Mexico, in 1991.
The discovery of the crater with a width of 149 kilometers and a depth of 20 kilometers supports the proof of Alvarez's hypothesis. Critics who questioned the location of the crater, if the asteroid hit the Earth answered through the discovery of Chicxulub.
University of Erlangen-Nurnberg geophysicist Peter Schulte explained that the asteroid hit a sulfate-rich region releasing sulfur aerosols. "We conclude that the Chicxulub crater was formed from a large asteroid object that was the main cause of the extinction of the dinosaurs 66 million years ago," said Schulte, quoted from the Berkeley Lab website.