fix the seabed and add gravel and dirt blobs into ground

mods/minecraft/mapgen.lua

@@ -36,6 +36,8 @@ minetest.register_biome({
 
 minetest.register_biome({
 	name = "sea",
+	node_top = "minecraft:sand",
+	depth_top = 1,
 	node_filler = "minecraft:sand",
 	depth_filler = 2,
 	y_max = -3,
@@ -69,4 +71,4 @@ minetest.register_decoration({
 
 dofile(minetest.get_modpath("minecraft") .. "/mapgen/bedrock.lua")
 dofile(minetest.get_modpath("minecraft") .. "/mapgen/ores.lua")
-dofile(minetest.get_modpath("minecraft") .. "/mapgen/trees.lua")
+dofile(minetest.get_modpath("minecraft") .. "/mapgen/trees.lua")

mods/minecraft/mapgen/ores.lua

@@ -1,6 +1,52 @@
 
 --- Ores mapgen!
 
+--
+-- Misc stuff
+--
+
+-- Dirt
+minetest.register_ore({
+	ore_type       = "blob",
+	ore            = "minecraft:dirt",
+	wherein        = "minecraft:stone",
+	clust_scarcity = 15*15*15,
+	clust_num_ores = 33,
+	clust_size     = 4,
+	y_min          = -62,
+	y_max          = 65536,
+	noise_params = {
+		offset  = 0,
+		scale   = 1,
+		spread  = {x=250, y=250, z=250},
+		seed    = 12345,
+		octaves = 3,
+		persist = 0.6,
+		lacunarity = 2,
+	}
+})
+
+-- Gravel
+minetest.register_ore({
+	ore_type       = "blob",
+	ore            = "minecraft:gravel",
+	wherein        = "minecraft:stone",
+	clust_scarcity = 14*14*14,
+	clust_num_ores = 33,
+	clust_size     = 5,
+	y_min          = -62,
+	y_max          = 65536,
+	noise_params = {
+		offset  = 0,
+		scale   = 1,
+		spread  = {x=250, y=250, z=250},
+		seed    = 12345,
+		octaves = 3,
+		persist = 0.6,
+		lacunarity = 2,
+	}
+})
+
 --
 -- Coal
 --