Geology

The following description applies (unless otherwise stated) to a Moon that is generated with three of the five options (Tree Cover, Terrain Roughness, and Exotic Terrain) set to the default (center) positions.

Surface Features

Hills

Hills tend to be less than 15 blocks high, but can be as much as 30 blocks high in rare cases. Increasing the "terrain roughness" or "exotic terrain" options causes the average hill height to increase, but does not cause much change in the maximum. Hills greater than 20 blocks high are always rare.

Part of the surface of this hill is a Gravel-filled void.

A Green Astronaut uses to edge of a crater for cover. Two other craters (partially submerged) can be seen in the distance.

Hills are almost always covered with the Topsoil; however, there will occasionally be patches of bare Dirt or Gravel. These patches are also found underground (described below).

Craters

Craters are fairly common, but are a bit hard to notice due to the need for a suitable vantage point.

Fault Lines

Fault Lines are a result of the terrain generation algorithms (see Superblock for more details). A pair of parallel fault lines is sometimes found at a distance of 128 blocks apart. In this photo the fault line runs from top-left to bottom-right in the photo. It is a vertical surface that is seen both above and below the Ice.

A "fault line" found between Superblocks, and a void filled with Dirt.

Underground Material Strata

The moon is composed primarily of six types of material: Ice, Topsoil, Dirt, Sand, Gravel and Rock.

Ice and hill, before excavation.

A hill viewed from the east (looking west). The hill and the ice to the left (south) are marked with red markers placed along a straight north-south line.

Cross-section of geological strata. Everything east of the red markers has been excavated down to a depth of 14 blocks below "ground level".

Ice

Ice fills all areas whose solid surface would otherwise lie below "ground level." These are commonly known as ice lakes.

Sand

Sand is light blueish-gray and is found below ice and near the base of hills. Its thickness is from one to three blocks (it will always be three blocks thick when found below ice).

Topsoil

Topsoil has a texture that is light at the top and brown on the bottom. Though it looks different, when you mine it you get ordinary Dirt.

Dirt

Dirt is brown all the way through. This is found in a three-block thickness below the Sand or Topsoil layer. Soil-filled regions are also sometimes found at deeper layers.

Gravel

Gravel is pink and gray. It is found in a five-block thick layer below the soil layer. Gravel-filled regions are also sometimes found in other places (either higher or deeper than normal gravel level).

Rock

Rock is medium gray. It is found below the gravel layer and extends all the way down to the bottom of the world (63 blocks below "ground level").

A More Complete View

After I worked out the internal data format of the game I was able to make accurate maps (and cross-sections) by inspecting the saved game data directly. Here is a more complete view of the hill cross-section:

Here we see 64 blocks down and a little further to the left and right.

Using cross-sections like this it was easy to see that there are small patches of both Dirt and Gravel, randomly placed, at all depths including above ground (as part of a hill).

Judging your depth

Because the layers have a uniform thickness, you can usually judge your distance below the surface while mining a tunnel.

Dotted line represents an imaginary tunnel.

Imagine mining a horizontal tunnel along the dotted yellow line.

If you see Sand, you are 1-3 blocks below Ice or are very close to the surface (the sand next to a hill).

If you see Dirt, you are probably either 4-6 blocks below Ice, or 1-4 blocks below the surface of a hill.

If you see Gravel, you are probably 7-11 blocks below Ice, or 5-9 blocks below the surface of a hill.

If you see Rock, you are more than 11 blocks below Ice, or more than 9 blocks below the surface of a hill.

Abundance of Materials

Material Abundances

Blocktype	Name	Block Number	Normal Abundance	Lowest Setting	Highest Setting
4	Rock	142325463	79.48 %	80.45 %	79.29 %
6	Gravel	15196585	8.49 %	8.59 %	8.41 %
2	Dirt	9921915	5.54 %	5.66 %	5.50 %
8	Water	5686554	3.18 %	2.10 %	3.50 %
3	Sand	4529147	2.53 %	2.45 %	2.37 %
1	Topsoil	1026339	0.57 %	0.58 %	0.62 %
19	Magnetite	105617	589.77 PPM	561.54	576.02
11	Aluminum Ore	68501	382.51 PPM	376.11	380.39
23	Titanium Ore	53065	296.32 PPM	284.57	293.98
7	Moon Leaf	42419	236.87 PPM		608.71
13	Gold Ore	37119	207.28 PPM	198.01	202.50
25	Notchium Ore	19390	108.28 PPM	104.92	109.83
10	Light	17703	98.85 PPM	0.88	273.90
28	Moon Wood	16710	93.31 PPM		299.25
21	Polymer	14668	81.91 PPM	89.23	86.72
27	Blue Crystal	9033	50.44 PPM	49.06	50.29
16	Sulphur Crystal	3823	21.35 PPM	18.14	18.18
43	Moon Bark	2946	16.45 PPM		62.34
17	Boron Crystal	1896	10.59 PPM	8.53	8.10
37	Sulphur Ore	679	3.79 PPM		12.69
32	Feldspar	500	2.79 PPM		12.48
34	Blue Stone	497	2.78 PPM		11.17
130	Disk	305	1.70 PPM	1.34	1.72
Overall Moon Stats
superblocks			166	200	230
sq. km			18.0	21.7	24.9
percentage with lairs			11%	13%	15%