Minecraft wiki entry for Cave, associated text: Caves are underground structures consisting of randomly generated cavities of air, water or lava, hollowing out an area and exposing other blocks generated with the terrain (such as stones and ore blobs) in the interior. Their structure typically consists of a series of irregular tunnels branching off and winding in other directions, which may connect to the surface, creating natural entrances to the cave. In jungle biomes, vines generate in caves near the surface. Sand often falls into caves generated near the surface of a desert or beach; craters in the sand can alert the player to caves below the surface. Caves cannot cut through red sand nor snow blocks, despite these generating as a surface block in several biomes.[1]