Guided by UCD geologist Eldridge Moores over a period of 15 years, John McPhee made numerous trips across northern California, from the Sierra to San Francisco. The result was McPhee’s _Assembling California_ (1993), a classic account of the geologic evolution of the Golden State, a book in which plate tectonicist Moores was a central figure. In this informal discussion, the two reflect on the experience and respond to questions about their relationship, the relationship between writing and knowledge, and about the place of science and the humanities in public life.