Using a previously derived model of the dry, amorphous, hydrophilic SiO2 surface, the reactivity of generic defect sites on the surface with respect to water, and the local network rearrangement that accompanies hydrolysis at these sites, is investigated using cluster models. Ab initio methods are used to calculate reaction barriers and reaction pathways. Consequences of the various types of hydrolysis product found are discussed with reference to potential sites for polymer chemisorption on the hydrolyzed, amorphous SiO2 surface.