In numerical simulations ofq=2 tearing modes, the maximum amplitude of the mode is found to increase rapidly as the safety factor on axisq(0) rises above 1.5. The associated magnetic islands grow to the center of the column, encompassing virtually the entire plasma cross section. As a result of the formation of these very large islands, the hot central plasma is rapidly convected out to the edge of the column, thereby destroying central confinement. Experimental evidence from several tokamaks linking the formation of these very large islands with major disruptions is presented. Typically, major disruptions are observed to occur in two (or more) stages. During the first stage(s)qrises on axis while the final stage, which terminates the discharge, is associated with the violent growth of anm=2 perturbation. Under some circumstancesq=2 sawteeth are predicted to occur. Evidence for such sawteeth in a divertor tokamak is discussed.