The Age of our Ocean Floors
The creation of Pangaea, several hundred million years ago, occurred when the two
major continental plates, Laurasia (N.America, Europe, Asia) and Gondwanaland (S.America,
Africa, India, Australia and Antarctica) collided.
Mid-Oceanic Ridges have been splitting the continents ever since. At a rate of about 10 cm/year, it takes 200 million years to cross the Earth. The ocean floors are not particularly old, because the old stuff is constantly being shoved under the continental material in subduction zones.
Historically Plate Tectonics was even greater in the past. The interior was hotter (all FOUR methods of heating was occurring initially) and convection was certainly much more active. In the first billion years, the crust of the Earth may have been much thinner, and not able to even remain as individual plates. Earliest evidence for individual plates and subduction zones (found in Canada) date to 2.7 b.y.a.