Why continental crust is older than Oceanic Crust?

Why continental crust is older than Oceanic Crust?

Answer: 

• An important difference between continental and oceanic crust is their difference in density. Continental crust has a lower average density (2.6g/cm3) than does oceanic crust (3.0g/cm3). This density difference allows the continents to float permanently on the upper mantle, persisting more or less intact billions of years. Oceanic crust in contrast, is barely able to float on the mantle (which has a density of 3.3g/cm3).
• As oceanic crust ages and cools, it accumulates a heavy under-layer of cooled mantle rocks; the resulting two-layer structure eventually sink of its own weight (because of its own weight) into the mantle, where it is melted down and recycled.

        Because of this process; no oceanic crust older than 200 million years exist on the earth.

• About 16% of mantle consists of recycled oceanic crust rocks; while only about 0.3% of mantle consists of recycled continental crust rocks.