What constitutes a material change in the circumstances of a child?

The definition of what constitutes a material change in the circumstances of a child, so as to meet the threshold test in s. 17(5) of the Divorce Act, was established in Gordon v. Goertz 1996 CanLII 191 (SCC), [1996] 2 S.C.R. 27, at paras. 12-13. I set out the relevant parts of those paragraphs: "12 What suffices to establish a material change in the circumstances of the child? Change alone is not enough; the change must have altered the child's needs or the ability of the parents to meet those needs in a fundamental way .... 13 It follows that before entering on the merits of an application to vary a custody order the judge must be satisfied of: (1) a change in the condition, means, needs or circumstances of the child and/or the ability of the parents to meet the needs of the child; (2) which materially affects the child; and (3) which was either not foreseen or could not have been reasonably contemplated by the judge who made the initial order."