Book excerpt: New Yorkers co-exist intimately with the traces of powerful geo forces. Apartments made of red sandstone from the Triassic both shelter us and populate our visual space. Rockefeller Center elevates and displays limestone from the Mississippian Period. The iron of the Manhattan Bridge stands as a message from Precambrian times.Geologic City: a field guide to the GeoArchitecture of New York visualizes the reality that modern life and geologic time are deeply intertwined. With the field guide in hand, residents and visitors are able to interact with familiar, even iconic New York architecture and infrastructure in an unexpected way: by sensing for themselves the forces of deep time that give form and materiality to the built environment of the City.