how long did it take california's landscape to form?

Answer 1

You haven't asked an easy question. Depends what you mean. The oldest rocks in California are Proterozoic. In general, older rocks lie on the eastern margins of the state. Most of the bedrock of California was added to the margin of North America during the Mesozoic.
The primary surface features (what you might call landscape), mountains and valleys, are much younger and are still forming. In southern and central California, the subduction of the edge of the Farallon plate and the subsequent development of the San Andreas fault system had/has a profound effect on the topography--creating basins and mountains, slicing across the southern part of the state and displacing rocks northward. In northern California, there is still an active subduction zone, with volcanism. The whole state is geologically active-pieces are going up, down, sideways, and (or) rotating.