In animations that show the location / drift of the continents over the aeons, it seems that the continents (or cratons?) are just floating / drifting around, sometimes fusing or splitting, but having almost non-changing cumulative surface area over time.
This rises the question how that asymmetry between continents and oceans originally formed. Of course continental crust is less dense than oceanic crust, and once formed the lighter one would just float around on the denser one.
Are there scientific theories how and when this originally started? Like in liquid, hot, early Earth, the lighter stuff would just form a less-dense layer covering the whole planet.
And then? Was it a smooth process of accumulating / clumping continental stuff over time, and after accumulation they just keep drifting around? Or was it some cataclysmic event like early Earth being hit by a Mars-sized object that formed the Moon, and that impact lead to a since-then persisting asymmetry in continents vs. oceans because some of the layers where ripped off locally?
note: Answers to What do continents "lay" on? do not answer my question because they don't even mention continent genesis.