return {
  -- metadata
  name = "underground",

  -- nodes
  node_dust = nil,
  node_top = nil,
  depth_top = nil,
  node_filler = nil,
  depth_filler = nil,
  node_stone = "colorlandia_colorland:gray_dark",
  node_riverbed = nil,
  depth_riverbed = 2,

  -- liquids
  node_water_top = nil,
  depth_water_top = nil,
  node_water = "colorlandia_colorland:water_source",
  node_river_water = nil,
  node_cave_liquid = nil,

  -- dungeons
  node_dungeon = nil,
  node_dungeon_alt = nil,
  node_dungeon_stair = nil,

  -- climate
  heat_point = nil,
  humidity_point = nil,

  -- y values
  y_min = -200,
  y_max = -100,
  vertical_blend = nil,
}