Minecraft wiki entry for Noise_generator, associated text: Stratum colors are determined using only the first 48 bits of the 64-bit world seed in Java Edition. The strata repeat every 64 blocks on the Y-axis, and the elevation of a particular stratum can vary through a biome by as much as 4 blocks. Stratum elevations vary with respect to the X-axis only, neglecting the Z-axis.