Answer: The Western Hemisphere contained significantly higher amounts of shock-fractured quartz. This led Walter and Luis Alvarez to hypothesize that the asteroid impact site was in the Western Hemisphere.
Step-by-step explanation:
On a geology expedition in Italy in 1980, physicist Luis Alvarez and his son, geologist Walter Alvarez, both of the University of California, collaborated. They unintentionally came across a region of sedimentary rock with abnormally high concentrations of the rare metal iridium. According to chemical dating methods, the rock is about 65 million years old. That coincides, coincidentally or not, with the end of the dinosaur era.
The Alvarezes proposed that the iridium, which had a very even distribution and wasn't just concentrated in Italy, was a byproduct of a massive asteroid striking Earth and releasing smoke, dust, and iridium into the atmosphere. The sun was obscured by that smokescreen, which decreased the temperature of the planet, killed plants (but not seeds or roots), and subsequently many animal species, including dinosaurs. The meat-eaters who would have devoured the plant-eaters perished first, then the plant-eaters. Due to their smaller size, fur, and capacity to consume seeds, roots, and decomposing flora, smaller mammals and birds were able to survive the cold, barren time. Iridium subsequently formed as a result of the pollution's eventual earth settling.
The theory is still up for discussion.