According to researchers, this theory is believed to have started 4.6 billion years ago. However much we shed light on theories that took place up to 3 billion years ago, the plate tectonic theory is not suffient enough to explain the earth's and crust formation before 1 to 3 billions years ago through to the earliest formation of planet 4.6 billion years ago. The difference with these numbers are big and it is simply hard to find well-preserved ancient rocks
The correct answer is - Rocks that are old are hard to find.
In order for the scientists to be able to study the beginnings of the plate tectonics they need a physical proof. The problem is that the oldest pieces of rocks have been subducted sometimes in the past, thus recycled in the mantle, so the proof is long gone. The oldest rocks on the planet, usually found deep into the mainland of the bigger land masses, are very rare, and very small, and on top of that, even though they are the oldest pieces of rocks, they are not the first ones that appeared, at least that is what is thought.
