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What kinds of caves are there?
- Tunnels: the backbone. Long winding galleries 2 to 9 m wide with flat floors, forks, rooms 7 to 16 m wide where they meet, entrances that open in the ground (a sinkhole is a steep ramp down) and ravines.
- Winding tubes: round tubes 2.5 to 4 m across that climb and dive at every angle. They are the ramps and shafts between the levels of the network.
- Caverns: halls 10 to 60 m wide on a flat floor 45 to 95 m down, with domed ceilings and stone pillars. They only exist in rare regions, about a tenth of the land.
Caves are sealed under any liquid: there is rock between a cave and a lake or the sea, so the water does not come in. Closed caves keep 3 m of rock over their ceiling, less on a steep hillside, where a tunnel can open onto the slope.
How deep do caves go?
- 200 mband under the surface where caves exist
- 5tunnel levels: 20, 38, 60, 90, 135 m down
- 160 msea level, so the bedrock is 160 m under a beach
| Depth under the ground | What you find |
|---|---|
| 2 to 48 m | Small coal and iron pockets on almost every cave wall (see where to find ores) |
| 12 to 80 m | Aquifers: pools of underground water in limestone, on a bed of gravel and clay |
| 20 to 160 m | Geodes: hollow spheres with a calcite shell and a crystal lining |
| 25 to 120 m | Oil pockets under a roof of shale (see how to find oil) |
| 45 to 95 m | Caverns |
| From 68 m under sea level | Deep caves: basalt, magma rock, glowing crystals |
| Flooded regions | Some cave regions are flooded. The flood is lava (three times in four) when its level lies below 94 m of altitude, water otherwise |
| At least 40 m under the surface | Lava lakes: domed chambers whose lava floor lies 6 to 30 m above the bedrock |
What do caves look like?
- Dripstone caves, the commonest: stalactites of calcite, stalagmites under them, columns where they meet, floors of gravel and clay. Under hot deserts, crusts of saltpetre.
- Lush caves under humid and mild land: carpets of moss, curtains of vines, glowing mushrooms.
- Frozen caves under cold land, within 40 m of the surface: floors of ice and icicles of packed ice.
- Deep caves from 68 m under sea level: basalt floors veined with magma rock, and clusters of glowing crystals.
- Everywhere, now and then, a lone crystal.
What is dangerous down there?
- Creatures. For monsters a cave is always night, at any hour of the day. Bats, spiders and golems live there, and magma golems den near lava. See night monsters.
- Lava. 15 points of damage a hit, about 3 s to die. Water on a lava source makes obsidian, on running lava makes stone, so a bucket of water is a good companion (see liquids and buckets).
- Falls. A drop of 3.5 m never hurts. Beyond it, 6 points per extra metre; about 20 m kills.
- Drowning. In a flooded cave you have 20 s of air, then 8 points of health a second.
What about the Moon?
The Moon has its own underground: vaulted halls 18 to 44 m under the inner worlds of its big craters, shafts that lead down from crater floors, fissures, overhangs, and lava tubes. Down there grow lunar moss, curtains of twilight leaves and crystal and quartz cones; ice fills the polar caves, and iron, ilmenite and meteoric-iron crusts line the walls (see where to find ores).
Questions
How do I find a cave?
Look for entrances in the ground, sinkholes and ravines, or dig down: tunnels sit at 20, 38, 60, 90 and 135 m under the ground.
How deep can I dig?
To the bedrock, at altitude 0, which is 160 m under a beach and up to 300 m under a summit. Caves only exist in the 200 m under the surface.
Is there always light underground?
No. Torches light the way, and lava, glowing mushrooms and crystals give light of their own.
Do caves flood?
Some regions are flooded, with water, or with lava when the flood level lies below 94 m of altitude. Elsewhere rock seals every cave from lakes and the sea.
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