“Of all the questions surrounding the Rolling Stone article that detailed Gen. Stanley A. McChrystal’s surprisingly blunt criticisms of the Obama administration, few are as puzzling as this: Why would a top military commander allow a journalist so much unfettered access to his inner circle?” “The answer, it seems, is a volcano.” Jeremy W. Peters looks at the reasons that led General McChrystal to mouth off to a publication devoted primarily to pop culture and the music business, and how the article hit the news before Rolling Stone itself had posted it.