as the NPs sublimed at high TNP, with particularly fast changes for TNP greater than the bulk silica Tmelt. 3. Pre-heated silica NPs held in O2-containing atmosphere etched vigorously at 1200 and 1300 K, with many similarities to the etching behavior of Si NPs at 1200 K. 4. Active etching continued at roughly constant rates as the NPs lost >50% of Minitial 5. If the experiments were continued long enough, the silica NPs all eventually passivated as shown by near-zero mass loss rates, often with relatively sudden transitions from active to passive etching behavior. Each point is discussed below.