What process or event was required for plate tectonics to begin on earth ?

The tectonic plates appeared when the earth began to cool, where the water flooded the earth. The earth that was submerged originated the tectonic plates.

Explanation:

Plate tectonics are large semirigid rock blocks that make up the earth's crust. The Earth is divided into fourteen main tectonic plates, which move slowly and continuously over the mantle, and can approach or move away from each other.  The movement of the plates results in the formation of mountains, oceanic pits, volcanic activities, earthquakes and tsunamis.

The formation of tectonic plates was a result of the cooling and flooding of the earth. When the earth began to cool, where water flooded the earth. The submerged earth originated the tectonic plates.