This paper proposes a general model for the formation of the defects, in silicon dioxide, which conforms to existing concepts involved in the migration of ions through SiO2and confirms Peek's law. Furthermore the interrelationship between the time required for the formation of any number of defects and the applied electric field is shown to be consistent with the presence of space charge limited ion currents in the oxide. Such currents are shown to give rise to enhanced Fowler-Nordheim emission of electrons into the oxide. In developing the model, a boundary layer approximation is used. The present results are consistent with the presence of large amounts of trapped mobile ions in the boundary layer. Such traps would lead to a boundary layer of which the thickness does not vary with time and which acts as a plentiful supply of mobile ions.