Include in your discussion a description of the way sea-floor spreading works. As one proceeds outward, away from the crest of an ocean ridge, the age of the basaltic ocean crust becomes older. This explains why water becomes deeper away from the crest of the ridge - because the ocean floor is sinking as it cools and becomes more dense F. Rifting and splitting apart of continents is unrelated to patterns of heat flow in the asthenosphere.
Continents appear to go through a supercontinent cycle every several hundred million years.
Evidence for this phenomenon may be the regular periodicity of mountain building, followed by evidence of rifting. The last such rifting episode occurred approximately 200 million years ago.