Gene Shoemaker, USGS deceased, constructed the first geologic map of Meteor Crater (a.k.a. Barringer Crater) in 1960. The lessons learned were applied to Shoemaker's mapping of the lunar surface. The crater formed about 50,000 years ago when a bolide struck Earth's surface. The "Guidebook to the Geology of Barringer Meteorite Crater, Arizona (a.k.a. Meteor Crater)" 2nd edition by Dr. David Kring is available for download at https://www.lpi.usra.edu/publications/books/barringer_crater_guidebook/ .