We derive a new model of structural relaxation in glass based on nonequilibrium statistical mechanics and the Stillinger model of inherent structures. Our model follows the evolution of a system from its equilibrium liquid state through an arbitrary cooling path and allows for the computation of macroscopic properties as a function of time. Using this new model, we have numerically demonstrated for the first time the connection between the topography of a potential energy landscape in 1-D and its corresponding fragility.