The Alvarez impact hypothesis dates to the early 1980s, about, I believe. I think I was in grad school at the time, anyway. 1940 even predates acceptance of Plate Tectonics. There was a huge leap in geological studies that dates to about the end of World War II because of major technological advancements. Seismic imaging, isotope chemistry, ocean investigations, etc. all jumped into existence and gave us a huge new view of the earth system. Just scratching at the surface before that.