It sounds like there are some geology changes anticipated in Release 2. Is there anything that players could research that would be helpful?
Hard to say... I'm going to try to add some new overall structures to it, and if people have favorites it might speed things up a bit.
First off, double thanks to Uristocrat.
First, he made the wonderful research-and-share Real Solid Density Values For Stones Thread (http://www.bay12forums.com/smf/index.php?topic=80022.0), which includes the ability to download some raws from the DFFD to match.
Second, he asked the question I quoted above, triggering the start of this thread.
Hopefully, he'll be helping contribute to it, as well.
So, general kudos to Uristocrat for his work on the subject.
The general basis upon which these suggestions rest is that you start out with a relatively "flat" map of layers, which then get altered and overwritten by new things that you do to them that push and shove or simply overwrite chunks of the terrain.
Now, then, onto the topics of geology that my own searching can turn up:
Rework Alluvial Layers
Alluvial layers right now are... silly, to say the least. You find gold veins in river beds in exactly the same way that you find copper veins inside of granite: long, snaking trails of solid gold that just sit in the sand.
Alluvial gold should be something more like a single nugget that just happens to be sitting in the river stream, not a vein. All the alluvials should be no more than a few randomly scattered pieces of rocks and minerals that happened to survive being weathered down by the elements to a small enough chunk that a river current could wash it away.
River Erosion Exposing Deeper Layers (and slopes of the layers)
Another problem of a silly-looking effect of the way that rivers behave, rivers do not "bend" the layers of the soil down with them. In games where I embark near a stream or river, I always see the river having cut the layers down ten to twenty z-levels of stone, but that stone remaining the same layers of soil and upper layers of stone all the way through.
Look at the Grand Canyon (http://en.wikipedia.org/wiki/Grand_canyon) to see how a river cuts through multiple layers of stone. Yes, the soil layers should remain all along any slope that isn't too steep for it to sit upon, but the stone layers should have been cut open and exposed by the sawing down of the stone that the river performed.
Instead, the layers appear to fold in order to accomidate the river.
Folding and Subduction
Wikipedia has a large and informative page on the subject of folding (http://en.wikipedia.org/wiki/Fold_(geology)), which is worth perusing on its own, but to boil this down to what would be ideal in the game setting itself...
Layer stones right now simply end cleanly, and trasition into the layer stones of neighboring biomes, having different soil types and stone layer types in a line straight down the map z-axis-wise. Layers are almost completely horizontal beyond the surface stone layer and the soil layers.
Folding involves the compaction of two different stone layers - typically causing one stone or the other to have to buckle or strain from the pressures exerted upon it. This would cause one layer stone to either slide over the other onrushing layer, or a layer of stone to buckle, and bunch up in a wavy accordian pattern.
Subduction is the even larger scale version of folding (http://en.wikipedia.org/wiki/Subduction), and involves an entire tectonic plate sliding beneath another plate, causing the layers of one to slant downwards into the earth, while the other is thrust upwards.
Regardless of the specific type of folding or subduction that takes place, they will make layers which do not lie perfectly horizontal. They make the transitions between different types of stone a much more interesting distinction than the simple transition from granite to limestome because you traveled westward from the forest biome to the grassland biome be a simple change in the type of soil you see.
They make small hills or dramatic cliff faces or volcanic mountain ranges or just plain make the subterranean layers go diagonal or even vertical.
See the Grand Canyon in this illustration (http://en.wikipedia.org/wiki/File:Stratigraphy_of_the_Grand_Canyon.png), with its multiple layers of sedimentary stone that accreated on top of the eroded, slanted basement rock.
Having diagonal stone layers (with horizontal sedimentary or soil layers on top) is just plain more interesting than simply having a randomly selected igneous intrusive or metamorphic layer randomly rolled up every 8 or so z-levels of depth. ESPECIALLY when it involves being able to learn about geology at the same time that you are looking for granite in the hopes of striking a cassiterite deposit.
Karsts
(Wikipedia) (http://en.wikipedia.org/wiki/Karst) Karsts are formations of carbonate stones - basically, Limestone, Chalk, Dolomite, and Gypsum - that have been eroded by acid rain.
As the acid eats away at the limestone, it expands through cracks, eventually creating massive spires and gullies that seem like fins of stone sticking out of the ground. This also creates naturally-occurring, non-magical cavern systems. Sometimes, both occur in the same location, resulting in massive stone outcroppings that have a grotto within them, such as the visually spectacular Ha Long Bay (http://en.wikipedia.org/wiki/Hạ_Long_Bay), or the karst cliffs along the Li River (http://en.wikipedia.org/wiki/Li_River_(Guangxi)).
Intrusions (Dikes, Batholiths, Plateaus, etc.)
(Wikipedia) (http://en.wikipedia.org/wiki/Intrusion) Intrusions occur when an existing layer of stone is "overwritten" by some geologic event, typically volcanic in origin.
When magma boils up to the surface, it fills in chambers, melting through or pushing away existing stone. These would produce odd bulges or small areas where the layers are different from the surrounding land without seriously changing the whole biome's overall layer structure.
The following are potential Intrusions that could be interesting to dig into:
- Dike (http://en.wikipedia.org/wiki/Dike_(geology)): A relatively small, thin, vertical shoot of igneous rock through the layers of stone, similar to how spoiler metal was thrown through layer stone back in 40d.
- Sill (http://en.wikipedia.org/wiki/Sill_(geology)): Another relatively small, tube-like chunk of metamorphic or igneous stone that is horizontal, and forms from magma squeezing in between the layers.
- Laccolith (http://en.wikipedia.org/wiki/Laccolith): A mound of cooled magma made of granite or diorite (felsic to intermediate igneous intrusive stones) that forms the shape of a hemisphere between two separate layers of stone. This has the effect of shoving the layers above the laccolith upward into a hill-shape to fit the bulge it has created in the earth.
- Lopolith (http://en.wikipedia.org/wiki/Lopolith): The inverse of a Laccolith, the Lopolith forms when magma squeezes between two layers, and the lower layer gives way before the upper layer gives way, making a hemisphere of igneous rock that pushes the layer below it downwards, rather than the layers above it upwards, forming an upside-down hill.
- Batholith (http://en.wikipedia.org/wiki/Batholith): Batholiths are similar to Laccoliths and Lopoliths, but are not as regularly-shaped. They are formed by multiple overlapping intrusions, and can become truly massive on a scale of several biomes, and can have very odd, lumpy shapes.
- Volcanic Plug (http://en.wikipedia.org/wiki/Volcanic_neck): essentially, a magma pipe whose magma solidified. This would just be a really big plug of igenous material shooting up through the layers of the earth. Granites, and to a lesser extent, diorites are generally hard enough that they will remain while the other layers the volcanic plug shot through have long since eroded, forming dramatic, nearly vertical plateaus of igneous rock.
Kimberlite Pipes
Technically a type of intrusion, I felt Kimberlite Pipes deserved a more specific explanation. (Wikipedia) (http://en.wikipedia.org/wiki/Kimberlite_pipe#Kimberlite_pipes) (History Channel) (http://www.youtube.com/watch?v=jmy601TdhM0&feature=related)
Kimberlite Pipes form from very rare, very violent, very pressurized eruptions of Ultramafic Magma, producing kimberlite and diamonds from the very high pressures.
In-game, Kimberlite Pipes would be similar to current magma pipes or volcanos that stretch a pipe straight from the magma sea to the surface, but would not have any active magma in it, instead being a solid conical plug of kimberlite (and diamonds) heading down deep into the earth. (Kimberlite would no longer appear as an alternate variety of gabbro. It should either appear as an ancient, deep layer near the magma sea (unless forced up to become a mountain), or it should appear as a kimberlite pipe.)
Kimberlite pipes are pretty much THE places where diamonds are mined. The only other way to find diamonds is to have them wash up in a riverbed from a place near a kimberlite pipe. Because of this, diamonds should be quite common here, and potentially all but impossible to find elsewhere (except as very rare single stones in alluvial layers).
Kimberlite is erodable into soil fairly easily as it is not as tough as felsic granite.
Pingos
(Wikipedia) (http://en.wikipedia.org/wiki/Pingo) A pingo is a layer of ice upon which a layer of permafrost has built up over centuries - something that only occurs in places where the ice never melts. This would only appear in tundra and glaciers, but would make them more remarkable for having literal ice hills so old that the dirt is growing over them, and they are practically layers of stone.
These are essentially just the Laccolith intrusion (listed above), except using ice instead of igneous stone.
Banded Iron Formations
(Wikipedia) (http://en.wikipedia.org/wiki/Banded_iron_formation) Banded Iron Formations are, simply put, whole (thin) layers of iron (magnetite and hemitite) that appear alternating between layers of chert and shale (and some other sedimentary layers) instead of as veins.
So, instead of having large, circular deposits of magnetite or veins of hemitite, it would be a single z-layer of that one material that follows the rest of the contours of the layers. Magnetite might not appear in any other way.
These are the major sources of real-world iron ore production, and were formed when the Earth's oceans were purged of iron through the introduction of oxygen to the oceans and atmosphere in the Earth's ancient past, forming a layer of iron ores along the surface of the ocean that was later buried by other sedimentary layers, and potentially eventually pushed up into the continental surface.
Mineral Deposit Rarity
Seriously speaking, the rarity of different minerals right now seems to be based almost entirely upon the number of layer stones they will appear within and the size of the deposits when they are present. This sort of distribution, where gold is as common as iron, really should stop...
Make Felsic, Intermediate, Mafic, and Ultramafic Layer Stones More Notably Different
The terms felsic and mafic refer to the mineral composition of magma. Magma naturally contains plenty of iron and magnesium from the Earth's core, as well as silicon and aluminum. This makes magma mafic (mafic being a term combining magnesium and ferric, the Latin word for iron)
The iron and magnesium, however, makes the magma denser, and can cool off and solidify at lower temperatures than silicon, leaving only the silacious magma still molten, and in that state, it is also less dense. In this state, it becomes felsic magma.
Felsic stones are less dense, lighter-colored, and often harder than their mafic counterparts.
Oceanic volcanos, with their thinner crust to break through, and constant eruptions are more mafic than the inland volcanos, with their rare eruptions and thick crusts. Mafic volcanos are generally less explosive and dangerous because of this.
Also, mafic stones (Gabbro/Basalt) are denser and more common where the crust is thinner - near the ocean. Most continents are primarily made of (felsic) granite at the lower levels. The probability of mafic or felsic igneous stones should therefore be a function of how much elevation there is - a mountain range should almost always be granite at its base unless it is an active island volcano or the result of some folding of a continental plate collision like California.
As I already discussed, ultramafic kimberlite and peridotite should be its own type of layer stone. Ultramafic stone is rare anywhere near the surface, but was common during the very early formation of the Earth's crust, and survives in the deepest portions of the crust, in places where the crust has been thrust upwards to the point where the deep peridotite has been exposed, and in kimberlite pipes. As I said in the kimberlite pipes section, diamonds would ideally only occur in kimberlite pipes.
Because these mafic and felsic stones are chemically different, it should follow that the ores you find in the stones and the way in which the stones erode in worldgen are different. Granite (intrusive felsic) is some of the hardest, most durable stone around, and makes up the base of most of the continents. Basaltic rock (extrusive mafic), meanwhile, is easily eroded down to black sand, and obsidian will functionally slowly dissolve in water.
From this site (http://ebeltz.net/classes/histgeo3.html), "Mafic rocks are high in iron and magnesium minerals, primarily Olivine, Pyroxene, Amphibole/Hornblende and aluminosilicate minerals like Calcium Feldspar/Labradorite and Calcium/Sodium feldspar mixes. Felsic rocks contain fewer iron magnesium minerals but are high in aluminosilicate Sodium Feldspar/Albite and Potassium Feldspar/Orthoclase, as well as sheet silicates/Biotite and Muscovite Micas and pure silica tetrahedrons/Quartz. Intermediate rocks contain some mafic minerals and some felsic minerals."
Wikipedia (http://en.wikipedia.org/wiki/Igneous_rock), also has a useful chart (http://en.wikipedia.org/wiki/File:Mineralogy_igneous_rocks_EN.svg) in demonstrating where you are more likely to find the orthoclases compared to the olivines.
The most difficult-to-find data, however, regards the most relevant data - which forms of igneous stones (especially the nearly-identical igneous extrusive stones) are more likely to contain what minerals.
This page is a Canadian Geological Survey, performed by the University of Ottawa (http://gsc.nrcan.gc.ca/mindep/synth_dep/vms/index_e.php). It is not an easy read by any means, and I say that being the guy who wrote (and researched) the massive Improved Farming thread.
Straining through the overflow of technical jargon and dry text, I found the following nuggets of useful data:
"As expected, the three deposit types dominated by mafic volcanic and volcaniclastic rocks have the highest Cu grades, whereas the two felsic-dominated deposit types contain the highest Pb and Ag contents. The bimodal felsic deposit group contains the highest average gold. Mafic-ultramaficdominated systems can also contain Se, Co, and Ni."
Mafic means basalt, and this says that they have the most copper (native copper). Selinium is not covered in the game, but Co is cobalt/cobaltite and Ni is Nickle/Garnierite. Felsic means rhyolite, and it has more lead and silver (galena, but also potentially just native silver), as well as gold. Shifting the way in which ore appears in game to favor this skewing would help differentiate the types of stone.
"Mafic-dominated, bimodal mafic, and bimodal felsic host rocks are dominated by effusive volcanic successions and accompanying, large-scale hypabyssal intrusions (Fig. 17). This high-temperature subseafloor environment supported high-temperature (>350°C) hydrothermal systems, from which may have precipitated Cu, Cu-Zn, and Zn-Cu- (Pb) VMS deposits with variable Au and Ag contents. Areally extensive, 1 to 5 m thick, Fe-rich “exhalites” (iron formations) may mark the most prospective VMS horizons (Spry et al., 2000; Peter, 2003) (Fig. 18A). These exhalite deposits consist of a combination of fine volcaniclastic material, chert, and carbonates. They formed during the immature and/or waning stages of regional hydrothermal activity when shallowly circulating seawater stripped Fe, Si, and some base metals at <250°C and precipitated them on the seafloor through extensive, but diffuse, low-temperature hydrothermal venting. Formation of exhalites on a basalt-dominated substrate was commonly accompanied by silicification and/or chloritization of the underlying 200 to 500 m of strata (Fig. 18B). Examples of this are observed in the Noranda, Matagami Lake, and Snow Lake VMS camps (Kalogeropoulos and Scott, 1989; Liaghat and MacLean, 1992; Bailes and Galley, 1999). In felsic volcaniclastic-dominated terranes, the generation of Fe-formation exhalites was accompanied by extensive K-Mg alteration of the felsic substrate, as recorded in the Bergslagen district of Sweden (Lagerblad and Gorbatschev, 1985) and in the Iberian Pyrite Belt (Munha and Kerrich, 1980).
Mafic, felsic, and bimodal siliciclastic volcanic assemblages tend to host volumetrically smaller mafic and/or felsic sill-dyke complexes, and generally contain Zn-Cu-Co and Zn-Pb-Cu-Ag VMS deposits, respectively. More Cu-rich deposits, such as Neves Corvo in the Iberian Pyrite Belt, may also be present in settings proximal to discrete extrusive complexes. The district-scale semiconformable hydrothermal systems consist of low-temperature mineral assemblages, with Mg-K smectite and K-feldspar alteration overlain by extensive units of low-temperature Fe-Si-Mn deposits. Other types of iron formation in VMS districts are interpreted to be products of plume fallout from high-temperature hydrothermal venting, or collection of hypersaline brines within fault-controlled depressions on the seafloor (Peter, 2003). Iron formation horizons can extend for tens of kilometres, as in the Bathurst VMS camp in New Brunswick (Peter and Goodfellow, 1996) (Fig. 18C), the Paleoproterozoic Bergslagen district (Allen et al., 1996b), the Devono- Mississippian Iberian Pyrite Belt in Spain and Portugal (Carvalho et al., 1999), and the Mississippian Finlayson Lake camp, Yukon (Peter, 2003). Mineralogical variations within these regionally extensive iron formations, from oxide through carbonate to sulphide, are indicative of proximity to more focused, higher temperature hydrothermal vent complexes and also reflect stratification of the water column in the basin. The mineralogical variations are accompanied by changes in element ratios such as Fe, Mn, B, P, and Zn (exhalative component) versus Al and Ti (detrital clastic component) (Peter and Goodfellow, 1996)."
Some interesting images are down near the bottom of the page, as well:
http://gsc.nrcan.gc.ca/mindep/synth_dep/vms/images/fig04.jpg
This one is especially good, since it shows the type of lava or magma produces that produces specific types of mineral wealth - the bottom right one, for example, shows a basaltic pipe filled with iron ores, among other minerals. Notably, it shows magnetite in a basalt layer.
http://gsc.nrcan.gc.ca/mindep/synth_dep/vms/images/fig22.jpg
http://gsc.nrcan.gc.ca/mindep/synth_dep/vms/images/fig11.jpg
As always, I encourage others to bring up their own research or expertise to help expand this list.