Synthesized answer
The provided passages do not contain enough information to explain the key concepts of the "Quiet Movement" in my own words. The passages only offer the title of a book, "The quiet revolution: grass roots of today's wilderness preservation movement by Donald N. Baldwin" [1]. Therefore, I cannot define or elaborate on any key concepts.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: The quiet revolution: grass roots of today's wilderness preservation movement by Donald N. Baldwin