Book excerpt: The contributions in this book explore several geologically significant sites and, in doing so, acknowledge and explore not just the geological exposures themselves, but also the people and issues that are fundamentally intertwined with the history of our science and its impact on our society. Through selective examples of outcrops and locales integral to the history of geology, we explore the evolution of modern geology, as well as the geodiversity and geoheritage of our planet. While the volume is far from comprehensive, the chapters contained herein detail a range for geoheritage value, scale of geoheritage sites and potential for geoheritage opportunities that will promote a broader, richer understanding of the complexity of the geoheritage of Earth. Importantly, many chapters offer a cautionary tale of sites almost lost to posterity and submit their take-away lessons for community mobilization towards geoheritage site protection.