Minecraft wiki entry for Custom_world_generation, associated text: noise_threshold [needs testing] conditional surface rule
 noise: [needs testing] default examples: minecraft: followed by one of: surface, surface_swamp, packed_ice, ice, powder_snow, calcite, gravel, patch, nether_state_selector, netherrack, nether_wart, soul_sand_layer or gravel_layer
 min_threshold: [needs testing]
 max_threshold: [needs testing]