How to instantiate chunks based on time.

I’ve been working on terrain generation similar to Minecraft’s, based on cubes. And now the last problem I find is that I can’t wrap my head around how to stop all the ‘chunks’ from generating at once. This is the function that I am using to instantiate the chunk prefabs.

void Update ()
		for (float x = transform.position.x - renderDistance; x < transform.position.x + renderDistance; x+= chunkWidth)
			for (float z = transform.position.z - renderDistance; z < transform.position.z + renderDistance; z+= chunkWidth)
				Vector3 pos = new Vector3(x, 0, z);
				pos.x = Mathf.Floor(pos.x / (float)chunkWidth) * chunkWidth;
				pos.z = Mathf.Floor(pos.z / (float)chunkWidth) * chunkWidth;
				Chunk chunk = Chunk.FindChunk(pos);
				if (chunk != null) continue;
				chunk = (Chunk)Instantiate(chunkFab, pos, Quaternion.identity);
				World.generate = false;

Help would be very much appreciated.

The whole loop can be done in a Coroutine, with a yield return null at the end of each iteration.
This will limite chunk generation to one per frame.