Looking Under Your World’s Skin

Now that we’ve seen your world move, it’s time to see what it’s made of – literally. What manner of resources and refuges lie in store for a delver on your world? Will your civilizations be built on a foundation of spongy clay or cold iron? These questions cover some important ways your cultures would be affected by the material they rest on.

The Ubiquity of Caves

Caves represent a classic fantasy setting – in games, perhaps the classic setting.* Weary travelers lost in the wilds can find refuge there, but caves are so rich in the trappings of habitation (both animal and human) that an explorer is more likely to find ancient relics or angry ogres than a good night’s sleep. More importantly, these things are better at moving a plot forward than “and then Jill slept soundly and nothing happened.”

“You enter the spooky cave to find… good lighting, walking paths, and tourists! Bwahahaha!” A view of inside Crystal Cave from the floating pontoon pathway by Captain-tucker used under CC BY-SA 3.0

Formation of these plot-convenient subterranean hollows is more a function of hydrology (water) than geology; the majority of cave systems* are formed by the eons-long erosive action of mildly acidic water on alkaline rock. That doesn’t mean geology doesn’t play a role. Geological processes are required to get soft sedimentary rock like limestone out of the sea and onto solid ground in the first place.

How would you give your world more caves – or even a complete underdark? Simple: use more limestone. Limestone* is what every large cave system is carved from. It’s required for stalagmites, stalactites, and most other beautiful and iconic cave features. In fact, limestone is a wonderful all-purpose bedrock for any fantasy setting. It also can be eroded to form otherworldly terrain on the surface, most notably the spires and oddities of Karst landscapes. The landscape gets especially weird if the alkaline rock has a broken top layer of harder “capstone” that prevents erosion in some places but not others. This forms the iconic mesas, buttes, pinnacles, and hoodoos of the American Southwest.

A view of the Karst landscape surrounding the Li River, in South China li jiang li river guilin yangshuo china 2011 karst raft by chensiyuan (license)

There are drawbacks to living on Karst: because the bedrock is porous, almost no water is available on the surface. Perhaps more importantly, valuable minerals are rare in limestone caves; the rock was made from shells, not gem-forming minerals or valuable metals.* Minerals can get into limestone caves, but they tend to be easily-dissolved things that aren’t super useful to humans. Caves with useful ores are more likely carved by glaciers or – more commonly – humanoids. Okay, so technically those count as mines, but who says your world wasn’t inhabited by a race of miners in prehistoric times?* Ore-rich mines might be a better option for your world because the availability of metals and minerals has a pivotal role in shaping its cultural history.

Technological Development of Civilizations

The type and availability of a setting’s mineral resources begs consideration. It’s not just a matter of which country is rich from gold mining, or where the hero found that shiny crystal. Civilizations are constructed, in a very real sense, from the materials they have discovered and mastered. It’s no coincidence that the ages of human civilization are named after game-changing materials. If your world is a close cousin of Earth, its civilizations are likely to progress along the same general track. That’s why it’s worth looking at the material driving forces of our world’s history.

The “big three” classifications – the Stone, Bronze, and Iron Ages – are more archaeological descriptions of an ancient culture’s level of technology than rigidly defined time periods. They represent a natural progression of technology, which is enabled by using more advanced materials. Though the names of these ages are intuitive, it’s worth remembering that bronze and iron don’t come from the ground as-is.  Humans had to figure out how to create them from their ores and work them into useful shapes. Even stone working was a complex, specialized task.

These ages overlapped; a Bronze Age culture could share a border with an Iron Age civilization. However, such situations were rarely stable. Bronze Age nations dominated Stone Age neighbors, and Iron Age technology was similarly a trump card over Bronze Age militaries. Cultures with advanced rivals had two choices in the long run: adapt the technology of their neighbors or be destroyed.* For this reason, boundaries between ages were abrupt by ancient standards – on a regional level, at least.*

Empire-destroying catastrophes result when imperialist late Iron Age / early Modern Age cultures decide to go on war-vacation in cities with Stone Age weaponry. Spoiler: it ends reeally badly for the locals.

After the Iron Age, better historical records led to different archaeological names reflecting the culture or empire (e.g., the Hellenistic Period, the Roman Period, the Colonial Period). Yet newly harnessed materials were still huge game changers, giving rise to what are informally known as Ages of Coal, Petrochemicals, and Silicon. And once we’ve begun exploiting space for its mineral wealth, expect a revolutionary Platinum Age.

Different Minerals, Different History

All of these Ages imply – no, demand – access to certain types of minerals or fuel sources. It’s likely that human history would have had very different Ages if we had access to a different set of minerals. As an example, let’s speculate about development on a very young* (As in, freshly accreted from a recent supernova remnant.)) Earth-like world. There hasn’t been enough time for fossil fuels to form,* but radioactive materials abound. There’s natural nuclear reactors, and alpha particles have produced vast amount of helium, which builds up underground and leaks out through surface vents. The ages of civilization could progress like this:

1. Stone Age. Akin to Earth’s Stone Age, but some of the stones cause strange sickness; the shaman says to avoid those stones.
2. Helium Age.* Early farming cultures discover that animal skins thrown over the vents of the squeaky-voice spirits will be lifted into the air. A large sack woven of animal bladders can hold enough spirit gas to carry a man into the sky! Flight becomes integral to society – though only warlords and high priests can fly on a regular basis.
3. Uranium Age.* Civilizations learn how to harness power (via simple turbines) from the natural nuclear reactors and how to handle radioactive material. These materials are also weaponized; if dispersed properly, they can make an entire city-state uninhabitable. There’s a good chance this age would not end well for most humans.
4. Metals Age. With reasonably advanced knowledge of chemistry and a source of insanely high temperatures (the natural reactors), early scientists uncover the secrets to many alloying and forging techniques in a fairly short span. This is good because their exposure to the reactors would doom them to death. These early scientists could become national heroes or martyrs: the mothers and fathers of metal.*
5. Age of Electricity. By certain loose definitions, “electricity” could be considered a material; electrons are a form of matter, after all. Electricity would likely be discovered early on this world, since radiation has a strange effect on (and produces directly, in some cases) electrons. Civilizations could be harnessing and transporting electricity in the equivalent of Earth’s Renaissance Era.
6. Modern Age. Or, more likely, the Age of Apocalypse via early nuclear bombs.* But hey, at least there’s no fossil fuels to bring about global warming!

Removing Earth-normal materials from your setting, or delaying access to them, is an intriguing exercise. What would civilization look like on a planet with no easily-accessible gold for use as a luxury good? To the ancients, gold was just rare and shiny – useful for hammering into gorgeous treasures or simple tools, but about as practical in battle as butter. Alternative currency models would arise,* but then what would happen when scientists of this world’s distant future discover vast deposits of gold hidden deep underground? Thus begins that world’s Gold Age* where gold transforms society as industrialists harness its high conductivity, unparalleled malleability, and nanoparticle potential.

What if there were no fossil fuels? The early industrial revolution was largely a consequence of the need for better technologies to safely extract coal from the ground. Those technologies led to more coal being extracted from the ground, which led to more machines using coal, which only spurred even better extraction technology. Without such a critical turning point, would technology take a different path, or would the standard of living be held back indefinitely? It’s difficult to answer these speculative questions with quantitative answers, but it’s fun to build a world around them.

The Polynesian Example

Trade, Migration, and War

The elements, minerals, and fuels that empower human civilizations are not evenly distributed around the planet. When we take an X-ray of Earth’s crust,* we notice that most minerals are concentrated in specific regions.  The most obvious example in today’s age of plastics and fossil fuels is oil.  We all know that the Middle East has plenty of easy slurp-it-from-the-ground oil,* and the region has become rich* and important as a result. Other examples abound: most platinum-based minerals are found in a small region of South Africa, and rare* earth elements come mainly from a single region in South China.

Uneven distribution of key resources is especially noticeable in the modern age because we know roughly where most minerals can be found and how much of them there are – and we’ve found uses for most of them. But that doesn’t mean resource distribution didn’t have a big impact on pre-modern civilizations as well. The rich coal deposits of Europe (and especially Great Britain) were an essential catalyst to the Industrial Revolution. The promise of gold and silver from the New World* drove early Spanish exploration and colonization efforts, which kickstarted the Columbian Exchange. “Mineral Rushes,” where individuals could seek their fortune, were not limited to the Gold Rush era of the Wild West. For example, serfs in 13th century Saxony could earn independence and wealth if they established a viable mine. Production of the Bronze Age’s namesake metal forced trade and conquest on its civilizations, as copper and tin (the two essential ingredients for high quality bronze) were almost never found in the same region.

Diffusion of metallurgy in Europe and Asia Minor. The darkest areas are the oldest. The earliest regions began working pure copper before alloying it with tin to form superior bronze. Note that good bronze requires both the green dots (copper) and blue dots (tin) – which are not commonly found together. Perfect recipe for trade.

If you need a resource to be scarce, look no farther than space.* There are minerals whizzing about up there – both real and imaginary – that are nearly impossible to find on worlds like Earth. Consider the mundane as well as the fabulous. Sure, kryptonite can rain down from the heavens. However, large amounts of iron-nickel alloy are more common, and they can propel simple cultures into an early Iron Age. Certain elements (platinum-group metals) are much more prevalent in asteroids than in the Earth’s crust,* and much of what we’ve mined originally came from space.

Uneven distribution of important mineral resources put the “geo” in geopolitics. Power dynamics depend on distribution of resources, and mineral resources are chief among these. A society can’t make their own mineral resources; they can only improve their access to existing deposits through trade, war, or improved mining technology. If your story needs a good excuse for a plot-convenient war, trade caravan, political intrigue, alchemical experiment, or wealth-seeking expedition, consider the tried-and-true justification: access to mineral resources.

We’ve seen how the material under your world’s skin can shape civilizations or just make it a weird place to live. Next time, we’ll see what geology means for your world’s most visually defining feature: its map.