U.S. Geologic Survey: Geologic Time Resources By Redefining Default | February 2, 2022 U.S. Geologic Survey: Geologic Time ResourcesFREE USGS: Grand Canyon Geology USGS: Introduction to Geologic Time USGS: Trek Through Time USGS: Geologic Time Activities for Kids (and kids at heart) USGS: Geologic Time Then and Now
