Two Vocal Styles, the Same Singer

Here I've included two videos of soprano Renee Fleming.  The first is Fleming singing Liu's aria from Puccini's Turandot and the second is a clip from her new Indie record, Dark Hope.   These recordings highlight a distinctive difference in vocal styles.  What are the characteristics of classical singing as opposed to a pop sound?  To quote pedagogue Richard Miller,  "Classical vocalism, as practiced in [...]