How One Geologist Proved Impact Craters Exist
Geologists said there are no impact craters on the Moon, so there shouldn't be any on Earth either.
Gene Shoemaker went to Meteor Crater and made a careful geologic map. The rock layers had been turned upside down. Flipped over. A volcano would never do that.
That was the breakthrough. He proved Meteor Crater was formed by impact. It broke the logjam. Now there are over 200 recognized terrestrial impact craters, including Chicxulub...the one that killed the dinosaurs.