Worldbuilding Guide Part 6: Planetary Mapping

*Links to previous parts: Part 1, Part 2, Part 3, Part 4, and Part 5*

Previously we created the physical and orbital properties of every large object in the system. To avoid making all of your objects cueballs, we must now map them and give them cool surface features, which can also help with awesome settings and stuff. There are many different methods of mapping, and you will almost certainly have to use more than one of these.

## Mapping with Temperature (Albedo)

Finding the temperature of a planet is a key part of the mapping process, and one which is very often overlooked. In general, the temperature of a planet averaged across all latitudes is approximated (***APPROXIMATED***) by this relation:

T ~ L1/4/D1/2
I say approximated because if you run it for Mars, for example, it's a bit off. If you run it for Venus, it's *way* off. Why is this? Because of a thing called the greenhouse effect, which is actually fiendishly complicated and really can't be put in a simple guide like this. Luckily, some nice people made this, which can calculate the temperature for us!

Albedo is a measure of how reflective a planet is. For example, a planet with a Bond albedo of 100 would reflect 100% of the light that hits it, and a planet with a bond albedo of 0 would reflect none of it. Therefore, lowering albedo increases absorption, thus warming the planet, and raising it lowers absorption, thus cooling the planet.

Conversely, raising the greenhouse effect traps infrared light, warming the planet, and lowering it traps less infrared light, thus cooling the planet. It's actually really difficult to predict exactly how much it does this though, and messing with it can bring about some really weird effects.

Therefore, it's best to mess with albedo, because that affects mapping way more than anything else does. And also it's best not to mess with greenhouse effect too much or else you get Venus, which is decidedly unbased. Now we could just stop here and log these in our sheet, but think about what is actually reflecting the light. Plants, mountains, rock, seas, clouds, and so on.

Spreadsheet time! Artifexian made a fantastic spreadsheet which is extremely useful for this sort of mapping. Simply plug in the different numbers in the green fields (the pink fields are very rough earth values for reference), and the albedo will show up in the bottom cell. Plug that into the calculator above, and if you dont like the results, mess around with the albedo some more.

Take the results and note them down for future reference. However, there are some huge simplifications in this spreadsheet: The ranges can be very wide to take into account different types of materials, meaning that you should probably choose something near the middle of the range and avoid the extreme edges. There's also a thing called the Fresnel Effect, which causes things at higher latitudes to reflect more light, which is ignored in the spreadsheet to keep the math from going completely out of hand.

Aside from these, cloud cover is assumed to be uniform across all biomes because uneven and ever-changing cloud cover basically requires a supercomputer to calculate in any reasonable length of time. Also, the reflectivity is based on the Electromagnetic Spectrum of our sun, as different materials reflect different wavelengths differently.

In summary, this method should never be the only method you use. It isn't a substitute for making plate tectonics, placing biomes in logical places, and so on.

## Plate Tectonics

Earth's crust is broken into fragments. Drifting on the currents of the mantle, these fragments, aka **plates**, move relative to one another. Because of this, various landforms are formed at the boundaries where these plates meet, like volcanoes and stuff. The specific landforms depend on what type of plates are touching and what direction they are moving relative to each other.

### Types of Plates

Plates can either be continental or oceanic. Continental plates are thick, Felsic in composition, and relatively low density. Oceanic plates are thin, Mafic in composition, and relatively high density. Plate boundaries come in three types: Convergent, Divergent and Transform.

   Oceanic-continental convergent boundaries look like this. As the plates collide, the denser oceanic plate is forced beneath the less-dense continental plate. Features created here include a subduction zone (aka ocean trench), earthquakes, mountains, and volcanoes. A real example is the west coast of South America.

   Oceanic-oceanic convergent boundaries look somewhat similar except everything's happening underwater. Expect to find more trenches, earthquakes, small mountains in the form of islands, and of course volcanoes. An example of this is the Mariana Islands.

   The last type of convergent plate boundary is continental-continental. Here, both plates are composed of buoyant rock, so neither will want to fully subduct, causing a lot of folding, faulting, and buckling, leading to the creation of very big mountains and a ton of earthquakes. An example of this is the Himalayas.

Now there are two types of *divergent* plate boundaries: oceanic-oceanic and continental-continental. Oceanic-oceanic plate boundaries are characterized by a **Mid-Ocean Ridge** with a rift valley at its crest, earthquakes, and where the ridge pops out of the water, volcanic islands. Examples include the Mid-Atlantic Ridge. Continental-continental divergent boundaries are basically the same thing but on land. Examples of *this* include the East-African Rift Valley.

You could technically have a oceanic-continental divergent boundary, but given that new crust is created at these boundaries, it would rapidly become an oceanic-ocean boundary.

Then we have the transform boundaries: oceanic-oceanic and continental-continental. Continental-continental transform boundaries are where two continental plates slide past each other like the San Andreas fault. Expect earthquakes. Now, oceanic-oceanic transform boundaries are actually quite cool. They occur alongside divergent boundaries. If you look at the Mid-Atlantic Ridge, you'l find that the actual divergent boundaries are offset by transform boundaries, a natural consequence of plate motion around a sphere. Like before, expect earthquakes.

So there we are! We now have all the plate boundary types! I'll compile them into a table for you. Keep this table in mind because we will be using it a lot to create believable maps.

Plate Boundary Types
 Ocean-ocean
 Cont-cont
 Divergent
 Cont-cont
 Transform
 Ocean-ocean

### Actually Mapping

Planets are three-dimensional objects, so its a good idea to map in three dimensions. Most fantasy maps look fantastic on a page but look weird on a globe. As such, this method (designed by Artifexian) requires two main programs: Photoshop or GIMP, and GPlates, but it's just as easy to do everything that will be discussed in this tutorial by drawing on a piece of paper and a styrofoam ball, so there will be no specifics of each program here.

Start off with an initial concept for what your planet's landforms will be like. This helps avoid inadvertent earth-cloning (continents in the same basic positions as earth continents), which is fine if that's what you want, but it's kinda overdone.

Next, create an equirectangular (width/height ratio = 2:1) map of your planet, and, if you wish, overlay a 12x6 grid on it. Before continuing, note what distortions are present in an equirectangular map. The closer you get to the poles, the more s t r e t c h ed out your landforms appear side-to-side. With this in mind, sketch your plate boundaries on the map, never ever touching the top and bottom and making sure that whenever a boundary crosses the left or right edge of the map, it resumes at the same latitude on the opposite edge. For reference, Earth has 7-8 major plates, about 10 minor plates, and a bajillion microplates. Also, try to ensure that no more than three plates interact at any given point.

GPlates is useful for ensuring that the poles don't look like garbage, so use it. If need be, do some edits. After this is complete, mark in which plates will be continental and which will be oceanic. The continental plates need not be *all* land, just predominantly land, and vice versa for the oceanic plates. Remember, earthlike planets will need most of their surface to be covered in water, so its a good idea to make your largest plate oceanic.

After this, mark in the direction plates are moving relative to each other with arrows on a separate layer. The most convenient method for doing this is deciding where your planet's mid-atlantic ridge analog will be, and imagining how all other plates will interact.

Now for the fun part, filling in the continents! Just draw lines where you want your coastlines to be and make em look cool. You don't need artistic ability here, function over form is what we're going for. It's not like there's a shortage of youtube tutorials on the artistic side of mapmaking. Just go look em up if that's what you want.

With continents in, you now know exactly what is continental crust and what is oceanic crust, so we can mark in what is happening at each boundary. Based on the landforms you expect to see at each boundary, throw down various landforms according to the above table. Islands are really helpful for selling the believability of a world, so don't skimp on those!

Make sure to include volcanic hotspots, like Hawaii. These leave island chains in the middle of plates, stretching off in the direction that the plate is moving away from. However, on continents they can form large calderas, such as the Yellowstone Supervolcano. As an optional final step, we can use GProjector to make and export an utterly absurd amount of reprojections of our map.

Tada! We've finished the first few steps in proper mapping!

## Realistic Climates

Now we have our plates and mountains and islands and whatnot. But we don't know what the land is like! Climate maps of the real world use a thing called the Köppen Climate Classification System. Here we will learn how to apply this system to our cool worlds. Also, to those tempted, do not make single-biome planets. They're rather boring and also aren't possible.

### Closely Resembling Earth

To start, we will need a map, ocean currents, and wind patterns (the latter two are detailed here). Next we can figure out the relative precipitation and temperature variations.

 Low pressure areas (ITCZ, PF)
 Onshore winds
 Warm ocean currents
 Windward side of mountains

The reason why I said "leeward" and "windward" side of mountains is due to a thing called Orthographic Lift, which means that the side of a mountain facing prevailing wind will receive a lot of precipitation, whereas the leeward side will recieve virtually no precipitation. Remember this table because we will be using it to help us refine our climate zones as we place them.

Basically the method is:

* Locate the rough zones
* Refine with temperature and precipitation in mind
* Compare and contrast
* Move onto the next biome.

#### The Hadley Cell

Start by marking off and ignoring all of your tall mountains, i.e. anything taller than 800 meters. Next, place your tropical climates. Tropical climates go in the equatorward half of the Hadley Cell, out to 15-20º north and south.

 Tropical Monsoon
If any landmass is on a large continent occupying the 30º N/S line, north or south of a large equatorial ocean, place some monsoon stuff there on the coast.
 Hot Desert
 Hot Steppe

#### The Ferrel Cell

Ferrel Cell climate zones have two main subtypes: Humid Continental and Subarctic Continental. These subclasses and their placements and features are detailed below.

Ferrel Cell Biomes
 Subarctic Continental (Boreal/Taiga)

Now, we fill in the subtropical climates, which will for the most part fill in the flanks of the Ferrel Cell continents. These come in six main subtypes:

#### The Polar Cell

There are only two climate subtypes to worry about here, Polar Tundra and Polar Icecaps.

Polar Cell Climates
 Polar Ice Caps

#### Finishing up

If you want you can fill out your islands. Same rules apply as previously. From there you can eyeball what percentage of the planet's surface each biome takes up and use the albedo section to find out your planet's albedo.

This method ONLY HOLDS for earth-like planets and even then not always. Refer to the next part for what to do if your planet differs from earth in several specific ways, such as it being retrograde spinning.

### Retrograde-rotating planets

For Retrograde-rotating planets, wind and ocean currents will run the opposite direction. All this flipping will mean that your climate zones will flip too. What was in the west is now in the east and vice versa. Reversing the wind direction will also reverse your rain shadows, so keep that in mind. Otherwise, place your biomes the same way.

### Hot and Cold Planet Climates

Now that we know how to construct climate models for planets similar in temperature to earth, let's mess with the temperature a bit.

#### Cold Model

Twenty thousand years ago, during the last glacial maximum, Earth was 5-6º C colder than it is today. Place your tropical forests between 0-10º N/S, but with less coverage than you would put on for a standard earthlike planet. Place your tropical savannahs out to ~15º N/S. In regions affected by warm currents, extend the savannahs out to about 20-25º N/S.

Next, place your deserts. On a Cold planet like this one, place your hot deserts between 10-25º N/S in the interior of continents and regions affected by rainshadows, cold currents, and/or offshore winds. Cold Deserts are between 25-35º N/S, and can be placed in the same type of regions as hot deserts. They can also be placed higher up than their Hot counterparts, and at altitude in hot desert zones. Hot steppes and tropical monsoons are similar to modern-day earth, albeit monsoons are reduced a bit and steppes are *only* a transition between desert and savannah.

Place your Humid Continental climates between about 30-50º N/S, as a reduction from what your original climate map would have been if it had the same temperature as earth. Place your Subarctic Continental climate between 40-60/65º N/S, skewing the zone equatorwards in areas affected by cold currents and offshore winds.

Place your mediterranean climates between 30-45º N/S in regions affected by cold currents, and place your humid subtropical climates between about 25-35º N/S in areas affected by warm currents. Place your oceanic climates between 40-55º N/S in regions affected by warm currents, as well as at altitude in Humid Subtropical regions.

Place your Ferrel Cell cold deserts in continental interiors between 25-35º N/S in continental interiors and rainshadows. Deserts in general should cover more of your planet than if it had the temperature of modern day earth. Cold Steppes should only be thin transition zones between cold desert and surrounding areas.

In the Polar Cell, place your polar ice caps above 45º N/S with the lowest extent being in regions affected by warm currents or onshore winds. Surround your Polar Ice Caps with Polar Tundra. In regions where you have low-latitude ice caps, the tundra will be a thin transition zone. Around high-latitude ice caps, your tundra will be expansive. But don't go below 40º N/S.

#### Really Cold Model

Roughly 640 million years ago, Earth was enveloped in a thing known as **Snowball Earth**, aka the **Cryogenian Period**. During this time, it's debatable whether the entire planet was englobed in ice or whether there was a surviving band of open sea at the equator, but lets take the second interpretation because its more interesting to map. (the first interpretation would just be a solid ice cap color map).

To start, place Polar Tundra climates on all of your continental landmasses between 15º N/S. Then, place ice caps from 15º N/S to the pole, possibly extending it northward where there exists a continental landmass, and filling the space with more tundra. Make sure the locations where the icecap borders the sea isn't just a straight line at 15º latitude, but wobble it a bit, to make it look more interesting and more realistic.

That's kind of it. Wahey!

#### Hot (ish) Model

Because I'm tired of typing, I'll just give you a table with all biomes and their locations that you can follow, based upon Earth's climate in the Eemian Period, the last interglacial, when it was 2-3 degrees hotter than it is today.

Note that this planet isn't *truly* a hot planet, it's only two degrees hotter than modern-day Earth. For a truly hot planet, the scenario below is a good fit.

#### Actually Hot Model

In a true hothouse climate the temperature gradient seen in the previous model largely breaks down, resulting in a planet that is near uniformly hot climates. The point of distinction is that no ice exists on the Earths surface long term cold weather can still happen (i.e. snow sleet and low temperatures) it is just far less common and ice can't remain stable on the surface melting or sublimating not long after its deposition. As such a hot house climate is defined by the complete lack of ice caps which means you will have far lower climatic variation globally with far weaker climatic circulation since there isn't a temperature gradient to drive the same sort of large scale wind patterns and currents, as such expect storms and cyclones to be largely responsible for heat transfer rather than sustained wind currents which will be far more likely to break up.

Biome wise it is a bit tricky to gauge what a hothouse climate would be like with modern vegetation since before the last Ice age grasslands didn't exist as grass as we know it didn't exist with the exception of the older bamboo like lineages. Modern grasses started to appear around 30 million years ago with the first true grasslands appearing only around 20 million years ago probably driven by nearby supernovae supercharging lightning activity on top of dry ice age climatic conditions and lower CO2 concentrations enabling grass to overtake forests for the first time in Earths history.

How grasslands would respond to a warming climate would be a critical clue in determining how climates would or would not differ from what we are used to. I would suspect that over all tropical forest cover would probably increase since it became the predominate biome wherever moisture was sufficient but there is no precedent for grasslands so it is hard to accurately gauge whether grasslands could maintain their dominance. I suspect not at least not without some form of allelopathic poisoning of the soil and or self conflagration strategies but evolution has a way of surprising us so the sheer possibility is there for world building.

## Minutiae

### Fossil Fuels and Ores

Fossil fuels and ores can play a huge part in the history of your world. Therefore, it is important to know where on your planet they would be placed.

#### Coal

Coal deposits are the remains of ancient tropical to subtropical swamps. Back when earth's climate was very warm and wet, plant life flourished in "coal swamps"; large, low-lying, waterlogged regions. The waters of these coal swamps were anoxic (containing little oxygen), meaning that plants that died and fell into the water didn't rot away entirely, but just got buried under more dead plants, eventually forming a compacted layer of organic material called **Peat**.

Peat is about 50% Carbon. If it were buried to a depth of ~4-10 km, pressures and temperatures present at these depths would concentrate it to about 60%, forming **Lignite Coal**, the lowest grade of coal. The more the coal is buried under successive layers of material, the more concentrated the carbon becomes and the higher the quality of the coal. **Bituminous Coal** is the most common and second-best type of coal, at roughly 70% Carbon concentration. The rarest and best type of coal is **Anthracite Coal**, which contains upwards of 90% Carbon.

So place your world's coal reserves (no need to specify which type) in locations which in the past were low-lying tropical to subtropical swamps. Place higher-grade coal in the foothills of mountain belts in these regions. Do *not* however place coal reserves in the interiors of mountain chains. The pressures there are such that 100% Carbon, aka **Graphite**, is created, which is famously not coal. Finally, place your peat reserves in modern-day low-lying wetlands.

#### Oil and Gas

Oil and Gas are hydrocarbons derived from the remains of ancient plankton, *not dinosaurs.* Much like the formation of coal, when the plankton died, they sunk to the lake or sea floor, accumulating and mixing with the clay found there, forming a muddy organic ooze. This was then buried and compacted, forming black organic shale, which is known to oil enthusiasts as **Source Rock**.

If the Source Rock is buried to a depth of roughly 2-4 kilometers, pressures and temperatures found at this depth produce **Kerogen**. Shale containing 25-75% Kerogen is referred to as **Oil Shale**. At greater depths, the oil is broken down to form **Natural Gas**, aka methane. Because of this, Oil can only form in a narrow window known as the Oil Window, typically less than ~6.5 kilometers. The Gas window is much larger, typically extending down to ~9 kilometers.

Oil shale source rock is not very permeable or porous, so drilling it doesn't yield much product. Luckily, oil and gas are less dense than water, so they'll try to escape the source rock and try to get above the water table. If not stopped, they will eventually reach the surface and create an oil/gas **Seep**. Therefore, for underground reserves, what's known as a **Trap** is required, and basically consists of a permeable layer of **Reservoir rock** beneath an impermeable layer of **Seal rock**. The oil and gas are generated in the source rock, rise up and collect in the reservoir rock because they are trapped by the seal rock.

Traps can be found at a variety of locations. Along the crest of tectonic folds, along fault lines, or near salt deposits.

**SIDENOTE:** Underground salt deposits can be found on land that was once subtropical deserts. Salt and lithium may also be "mined" in salt pans, large dried-up desert lakes and ponds where evaporating water concentrated the salt and lithium in the remaining basin.

Therefore, place your oil and gas reserves in regions that were once shallow seas and lakes, but were then buried by sedimentary deposits and underwent tectonic compression. Additionally, secondary oil and gas reserves can be placed in sedimentary basins along passive continental margins. A sedimentary basin is a depression that has been filled with sedimentary deposits, and a passive margin is where the land meets the sea sans plate boundary.

Finally, place oil deposits in **Foreland Basins**. Foreland basins are depressions on the continental side of a mountain belt, filled in by sedimentary deposits just like sedimentary basins.

#### Ores

Metals occur natively (in their pure form) or as minerals (bonded to nonmetallic substances). If a concentration of a metal in a mineral is significant and the metal can be easily extracted, the mineral is referred to as an **Ore**. When an economically significant concentration of an ore occurs, it is said to be an **Ore Deposit**. Ore deposits form in many ways, and are usually associated with volcanic activity.

In a **Magmatic Deposit**, ore minerals precipitate in an underground magma chamber. In a **Hydrothermal Deposit**, hot groundwater dissolves the minerals and carries them away, precipitating them into the surrounding rock. In a **Submarine Vent Deposit**, ore minerals precipitate onto the ocean floor via black smokers near divergent oceanic plate boundaries.

These are some of the ways they form, now where do they go? Most of your planet's geologically recent ore deposits will form around volcanically active plate boundaries, in the overriding plate in subduction zones as well as in hotspots. Most of these deposits will be **Porphyry Copper** deposits, which come in the subtypes of **Copper only**, **Copper-Gold**, **Copper-Molybdenum**, **Molybdenum only**, and **Tin-Tungsten**. In all cases, there will be minor amounts of Lead, Zinc, and Silver.

Next to these deposits, trailing away from the volcanically active region, place your **Epithermal Gold** deposits. Start with **Gold**, with minor amounts of Silver and Copper, then further out place **Gold**, with minor amounts of Silver, Lead, and Zinc, then further out again place **Gold**, with minor amounts of Silver, Lead, and Mercury.

Surrounding these, place your **IOCG** (Iron Oxide-Copper-Gold) Deposits. These are associated with slightly older rock, and are important sources of **Uranium**. These can also be placed in continental rifting zones. Next, place your **Nickel-Copper** and **PGE-Chromium** deposits. These should be very rare and should go in your Ancient Cratons; old, stable interior regions of continents, away from plate boundaries. By the way, diamond deposits can also go in these regions, just make them very rare.

**VMS** (Volcanogenic Massive Sulfide) Deposits are found in both new and old mountainous regions. These predominantely **Zinc-Copper** deposits formed on black smokers on ancient seafloors, where subsequent mountain creation pushed them upwards to mineable depths. Expect minor amounts of Lead, Silver, Gold, Cobalt, Tin, Selenium, Manganese, and Cadmium.

For similar reasons, place **BIF** (Banded Iron Formation) deposits in and around old mountain chains. Back when Earth's atmosphere was super oxygen-rich, oxygen dissolved into the seawater, changing its chemistry such that it no longer could hold iron in solution. The Iron precipitated onto the seabed as iron oxide, sank, and formed layered sedimentary deposits on the sea floor.

Place **SedEx** (Sedimentary Exhalative) deposits of mainly Zinc, Silver, and Lead in your continental sedimentary basins. These should be fairly uncommon. Finally, place Residual Mineral Deposits of mainly Aluminum in your rainforests and other similarly wet regions.

Sidenote, you can place Secondary Enrichment zones a little bit downhill from some of your existing deposits, caused when the water table leeches and concentrates minerals away from the original deposit. In particular, make your dominant Uranium deposit a secondary enrichment zone.

MVT, Mississippi Valley Type deposits, form when groundwater sinks beneath a mountain range, dissolves metals, then transports and concentrates them in a new deposit on the other side of a Foreland Basin. Throw down some of these, too! Note that MVT-type deposits can be hundreds of miles away from the original deposit.

Finally, we have Placer Deposits. This is where a mineral or native metal outcropping erodes, enters a river system, and gets concentrated downstream. This is why panning for gold and diamonds actually somewhat works.

And that is all! By the way this is overly simplified but it should be enough for your purposes, as even the overly simplified version is overkill-complicated.

### Rivers

To create viable river systems, you'll need to figure out how water will flow over the topography of your map. To do this, mark out the ridges of your main mountain ranges and highland regions. These will be your drainage divides, and the areas they create will be your **Drainage Basins**. Next, roughly mark in your minor ridges. Using these, carve up your drainage basins, which will be quite large, into smaller river basins of varying size.

Next, place a primary river in each of your basins. Some tips: run your river from areas of high elevation to areas of low elevation. Run them in between your ridges and through your valleys. Make sure they take a fairly direct path, as any overly complicated courses with sharp turns will be rapidly eroded into the aforementioned fairly direct paths. Don't do splitting either except in the case of river deltas.

Next, add in some tributaries following the same rules as before. Then some tributaries of tributaries and maybe one more layer.

Note that in temperate or tropical regions, there will be many revers, which will be permanent, gaining rivers. That is, they will exist year-round and the volume of water flow increases in the downstream direction. Arid or Dry areas will tend to have fewer rivers, which will be ephemeral, losing rivers. That is, they only flow in the rainy season and the volume of water decreases in the downstream direction.

#### Features

Now that we have our rivers, now we should figure out what riverine features we would expect to see along their courses. We can divide a river into three parts, youthful, mature, and old age. The Youthful stage of a river is the stage during which it is in the mountains. This is where a river begins its journey. The gradient of the land is steep and the flow of the river is fast. The river channel is deep, narrow and V-shaped during this stage. Expect valleys, canyons, rapids, and waterfalls.

The Mature stage of a river is an in-between hilly stage. The gradient of the land is moderate, and so is the flow of the river. The river channel is wider, shallower, and U-shaped. Expect mild meanders, braided streams, narrow floodplains, and terraced floodplains. Finally, the Old stage is the last lowland stage of a river. The land has a shallow gradient, the river flows slowly, and the river channel is shallower and wider again. Expect extreme meanders, broad floodplains, oxbow lakes, yazoo streams, and deltas.

A river will begin at a source, usually a mountain spring or meltwaters from a glacier. If the water passes over relatively soft underlying rock, the fast-flowing river will carve out a V-shaped valley with interlocking spurs. If the underlying rock is relatively hard, slot canyons will form. If it alternates between hard and soft, expect stair-step canyons, like the grand canyon. If glaciation occurs, a glacier can erode a V-shaped valley into a U-shaped valley. The interlocking spurs are truncated, and hanging valleys form.

Rapids form whever a river passes over large rocky debris or a sufficiently steep gradient, and waterfalls form wherever an escarpment of hard rock is met. As the river leaves the mountains and enters its mature stage, the river's channel may become choked with mud and loose gravelly sediment. If this happens, the river will split into numerous interweaving channels. This is referred to as a **Braided Stream** and the deposits are called **Braid Bars**.

The river will also begin to meander slightly, though it won't be as curved as it will be in its old stage. On the outer curve of a meander, there will be a steep **Cut Bank**, and on the inner curve, the river will deposit gravelly sediment in a wedge-shaped **Point Bar**. Flooding in mature-stage river valleys can leave deposits of **Alluvium**, deposts of clay, silt, and sand, creating fertile **Floodplains**, which will be fairly narrow in the mature stage. If a river cuts down into a floodplain after its formation, it creates what is known as a **Terraced Floodplain**.

As the river exits the hills, it enters its old age stage, crossing the **Fall Line**. The Fall Line is the imaginary line delineating the upland and coastal regions, where rivers plunge, or "fall", at roughly the same elevation. Important cities or touns can often be found along the fall line as it marks the point at which boats can no longer travel upstream and the energy generated by the falls can be used to power various things.

Beyond the fall line, the river's floodplain will widen, and its meanders will become increasingly more pronounced. We will still find cut banks and point bars, only now the point bars will be soft and sandy. Also, meanders get curvier over time. If the curve gets too extreme, a **Meander Neck** is formed. Eventually, the river will cut through the weak meander neck, rerouting the river. The remaining meander is called an **Oxbow Lake** if it remains filled with water, and an **Abandoned Meander** if it dries up. A river may also split to form *small* river islands.

Interestingly for history, the ever-evolving paths of meanders can lead to very interesting territory disputes, as nation boundaries are frequently marked by rivers.

Deposition during flooding can lead to low ridges called **Natural Levees**. In regions where large natural levees form, low marshy swampland may form on the other side of the levees. Levees may also drop small tributaries from entering the main river, and adorably named **Yazoo Streams** flow parallel to the river in the floodplain.

    Where the river enters the sea, a **Delta** may form. Sediment carried by the river deposits at the river mouth to form a **Midstream Bar**, causing the river to split. Each new distributary forms another midstream bar, and repeat. If the ocean currents are significantly stronger than the current of the river, no delta will form because the ocean current will sweep away the sediment, preventing the formation of a midstream bar. If the ocean current is only slightly stronger than the river current, deposition will occur, leading to the creation of a classic triangular delta. If the current hits the river mouth head-on, it will form a curved-sided, V-shaped **Cuspate Delta**. These are the most common instances. In rare cases, if the river current is much stronger than the ocean current, the river will form a **Bird's foot Delta**.

#### Lakes

Lakes can go basically anywhere along a river's course, although they are generally more common in highland regions. Mountain lakes can be placed in depressions caused by tectonic/glaciation activity and volcanic craters. Plunge pools from waterfalls are also classified as small lakes. In lowland regions they can occur where a river widens into a basin or in floodplain depressions. The important thing to note is that several rivers may flow into the lake, but only one may flow out. Also, little mini-deltas may occur where a river enters a lake (or, for that matter, a much larger river!).

#### Formulae

You can *very roughly* calculate how wide a river should be, in meters by the following formulae, where **R** is Rainfall (1 = 1,000,000 m3 per year), A is the area drained by the river (1 = 1,000 km2), B is the Provisional Width, and F is the depth factor.

**B = R/4 • A • 0.1**
**W = B/F**
Take the value from the first equation and input it in the second as **B**. If B is 20-100, F=2, if B is 100-200, F=3, if B is 200-500, F=4, and if B is greater than 500, F=5.

Also, turns out rivers don't meander randomly. The ratio Width of river**:**Radius of meander curve**:**Length of meander (one s-shaped length) **=** 1**:**2.3**:**11.

#### Exotica

Fun fact: Rivers sometimes cut through mountains. This occurs when a mountain-building event takes place in between the source and the mouth of the river. If the river erodes as fast as or faster than the rock is being thrusted up, the river is not redirected, and a **Water Gap** is formed.

Do all rivers empty into the sea? No. An **Endorheic Basin** is a depression in the land where water is allowed to flow in but cannot flow out. Instead, evaporation is the only mechanism by which water can reenter the hydrological cycle. In wetter regions, you can place salt lakes in these endorheic basins, in drier regions, you can place inland delta swamps, such as the Okavango Delta in the Kalahari desert.

Do all rivers need to be contiguous? No. Some rivers disappear and reappear. In **Karst Regions**, regions where a lot of limestone, dolomite, and gypsum are present, rivers may disappear down sinkholes and caves, flow for a while as **Subterranean Rivers**, then reappear downstream.

And that's it. All the interesting stuff about rivers and how to make them!

### Coastal Landforms

Coasts vary dramatically in terms of landforms and topography, making them difficult to classify. For now, let's say that in our world, coasts come in two types, rocky coasts and sandy coastal plains. To mimic earthlike conditions, we should say that our coasts alternate between these two types.

Rocky coasts dominate on active plate margins, near coastal mountain ranges, and near regions affected by glaciation. Sandy coastal plains will be found on passive margins and on areas of low relief. The split will basically be about 80-20 in favor of rocky coastline.

#### Rocky Coasts

The primary features of high-relief, erosional rocky coasts are cliffs and shore platforms. A cliff is a near-vertical rock exposure. If the top of a cliff is rounded via weathering, it is called a bluff. Cliffs and bluffs may be punctuated by coves and gorges.

Coves, small circular bays, form on *concordant coasts*. These are coasts where bands of rock of varying resistance lie parallel to the shoreline. A small gap is cut in the more resistant rock, and then a wide circular bay is carved out of the less resistant rock. The sea or a river can do this. Multiple coves can corm in sequence, sometimes merging. Gorges occur when a vertical strip of weaker rock running through a cliff is eroded by wave action. Simple!

Shore platforms are platforms of rock extending from a cliff base that are only visible at low tide. They can be horizontal or they can slope gently downward. If no platform is visible at low tide, the cliff is a plunging cliff. Shore platforms are rarely smooth and are usually pockmarked with depressions and protrusions, scored ridges, gullies, and dotted with rock pools that make neat ecosystems, as well as marine potholes–cylindrical bowl-shaped hollows.

Platforms form when cliffs retreat. Waves cut a notch in a cliff, which becomes overhanging. The overhang becomes unstable and collapses into the sea, leaving a small shore platform, rinse and repeat.

Rocky coasts generally start very irregular, with headlands and embayments everywhere. Nature will seek to smooth things out by preferentially eroding away headlands. As they are eroded, headlands leave some cool-looking landforms.

Wave action will carve sea caves into the sides of headlands. These may have associated *blowholes*, or marine geysers, which are holes in the roof of a sea cave that large fountains of sea spray are often ejected from. If a blowhole becomes too large, it may collapse, forming a sinkhole. The sea caves will eventually erode their way through the headland, forming a sea arch. This will soon become unstable and collapse, forming a sea stack.

The sea stack protects the adjacent shore from the waves, so a buildup of sand and other debris can form. This slowly builds out a thin ridge of sand and gravel between the stack and the mainland known as a *tombolo*. This sounds like a planet name.

The sea stack will soon erode to a sea stump and eventually disappear. In summary, the evolution of a rocky sea coast is this:

Headland>Sea cave>Sea arch>Sea stack w/ tombolo>Sea stump>gone

Finally, if the sea level rises and/or the land sinks, the coast is said to be submergent. If the sea level falls and/or the land rises, the coast is said to be emergent. Emergent rocky coast may feature extra high cliffs or uplift terraces, where former shore platforms are lifted out of the sea, becoming cliffs, and new shore platforms are created. You can also get raised sea caves hundreds of meters above sea level.

The major submergent rocky coast is the fjord coast, which is discussed in the glacier section. A lesser known one however is the Dalmatian coast. This occurs when tectonic activity creates a series of folds running parallel to the shoreline, a concordant coastline. Erosion occurs, breaking holes in the more durable rock and eroding the less durable rock entirely away, forming a series of rocky islands parallel to the new coastline. The prototypical example of this is the eastern coast of the Adriatic Sea. They look very cool and earth should have more of them.

#### Coastal Plains

The most obvious and beloved feature of low-relief, depositional coastal plains is the beach. There is actually a very high variety of beach types in various places on Earth that I encourage you to look up to avoid spamming generic long white sand beaches that are all clones of each other. However, I don't actually know that much about them and it would add ten paragraphs that I really don't feel like writing. Someone else who actually knows this kind of thing can though! In the spirit of simplification, we'll say that there are two types of beaches: Pebble beaches and sandy beaches.

Pebble beaches consist of coarse, cobble-like material and are usually found near cliffs. They can occur at any latitude but are more common near mid-high latitudes, as glaciers are great sources of coarse material.

Sandy beaches are composed of fine sediment like

*checks notes*

sand, and can be found basically anywhere, though they are particularly common in the tropics. The color of a beach is determined by the color of the sediment in its surrounding environment. Beige, white, pink, black, red, orange, and green are all supposedly possible colors for a beach. Beige is the most common color and is caused by high quantities of quartz and iron. White is caused by quartz, limestone, feldspar, and gypsum and are particularly common in the tropics, especially on tropical islands. Coral white beaches specifically are also found where there's lots of remains of corals and mollusks.

Coral pink beaches are quite rare and should be limited to tropical islands. The color occurs when the remains of reddish corals wash up onshore. Black, red, orange, and green are also quite rare and are usually the result of some form of volcanic activity. Thus, place them sparingly in your volcanically active regions. Black specifically is caused by basalt and obsidian, Red is caused by oxidation of iron from volcanic rocks, orange is caused by high iron content or orange limestone, crushed shells and volcanic deposits, and green is caused by high amounts of olivine.

Beaches often, though not always, have a dune system associated with them. The largest dune systems occur in the temperate zone where strong onshore winds are present. Refer the the wind map you will create in part 7 for this. Dune systems are usually less common in polar and tropical regions. As previously mentioned, coasts will alternate between rocky and sandy coast.

In some places, asymetrically curved beaches will link rocky headlands. These are known as logarithmic spiral beaches because their curves are exact logarithmic spirals.

Most landforms associated with coastal plains are caused by *longshore drift*, the transportation of beach sediment parallel to the shore along the coastline. An incoming wave would send water up the beach at some angle, then water goes back to the sea perpendicularly to the coast. This produces the longshore current, and a sawtooth motion will drag beach material along the beach in the direction of the current.

Where the coast indents at an angle of greater than 30 degrees, like at an estuary or bay, the longshore drift builds a sand spit into the open ocean. In some cases, this can stretch all the way across a bay and form a lagoon. An example of this is Venice.

Sand spits come in a load of flavors. Recurve spits form when a spit curves back towards the shoreline in response to changing wind and wave conditions. If multiple recurves occur, then it is called a compound recurve spit. Comet-tail spits form in the lee of islands where longshore drift acts on beaches on either side of the island. If two comet-tails merge, a looped barrier is created, enclosing a lagoon.

Lagoons are bodies of shallow, quiet water protected from the open sea by some sort of barrier. Paired spits form when a spit grows out of either side of a coastal opening, like a bay or estuary. Cuspate spits occur where two opposing longshore currents meet. They are triangular-shaped and wider than they are long. There's also tombolos, which we previously discussed. If several islands are connected in a chain to the mainland in this manner, we call it a tombolo cluster.

A barrier beach forms when a spit grows across most if not all of a bay, or where paired spits merge, or when waves deposit material in an offshore bar in such a way that the bar grows above the high water mark. The water bewteen the barrier beach and the shoreline becomes a lagoon. Storms may breach the barrier beach and create narrow inlets, dividing the barrier beach and creating a chain of barrier islands. Barrier islands can occur on most coasts, but most of them are on passive margins.

Like before, emergent coastal plains can feature terraces, called raised beaches. Submergent coastal plains form estuaries. Which leads us tooooooooooo

#### Estuarine Coasts

Estuaries are long and narrow tidal inlets that connect to the open sea. They function as a transition zone between the freshwater river and the sea, as freshwater and salt water mix. Their associated coasts are called estuarine coasts and are almost always submergent in nature.

Generally, estuaries come in four types: Drowned river valleys, bar built estuaries, tectonic estuaries, and fjords. Drowned river valleys are coastal plain estuaries that form when sea levels rise and flood the region around the river valley. They have a characteristic dendritic pattern, and the prototypical example is Chesapeake Bay.

Bar-built estuaries, also known as restricted mouth estuaries, are essentially the same except that they have significant barring across their mouths. The prototypical example is the Outer Banks of NC.

Tectonic estuaries form when tectonic activity causes large regions of coastal land to sink, which is then flooded by seawater. A classic example is San Francisco Bay. Finally, everyone's favorite, fjords! Fjords are long, steep-sided, flooded glacial valleys. They form in mid to high latitude regions that were once subject to ice age glaciation. After the glacier that carved the valley melts, its water enters the ocean, the sea level rises, the valley drowns, and look at that it's a fjord.

#### Organic Coasts

Organic coasts are coastlines on which living organisms control the landforms. Tidal flats, also known as mud flats, are regions of mud and silt which can be found in the intertidal zone in regions protected from strong wave action. These can especially be found in lagoons or on shores protected by barrier islands. Tidal flats occur in association with coastal plains, and go between totally submeged at high tide and exposed at low tide. A tidal flat will usually have several tidal channels flowing through it as well as a huge number of tidal creeks. If the tidal flat is high enough, salt-tolerant plants will start to colonize the flat, forming a coastal wetland.

Mangrove swamps and salt marshes are the two primary types of coastal wetland. Salt marshes are populated by salt-resistant herbs, grasses, and low shrubs. They can occur practically everywhere, but the largest ones occur in the temperate zone on low-lying, ice-free coasts, bays, or estuaries. They will also likely occur on the landward side of spits or such structures.

Mangrove swamps are dominated by salt-loving trees – your planet's version of the mangrove – and are limited to the tropics and subtropics unless your version of the mangrove has different temperature tolerances.

Coral reefs are by far the most beautiful of any organic coast structure. They form in clear, well-lit, warm water and so are limited to the tropics and subtropics. If a volcanic island builds itself up out of the ocean, a fringing reef may form around it. This is a coral reef that extends almost to the shoreline, and are also found on continental tropical coasts. As the island moves off the hotspot, it will slowly erode and sink. However, the coral reef will continue to grow, forming a small island surrounded by a lagoon and a barrier reef. Eventually the island will become fully submerged, forming an atoll, and finally the reef itself will finally collapse, forming a flat-topped submarine mountain known as a guyot. In summary, the evolution of an island and its reef is essentially this:

Island>Island + Fringing Reef>Island + Barrier Reef>Atoll>Guyot

#### Summary

In summary, your coastline essentially alternates between rocky and coastal plains. Rocky coasts dominate and mainly go on active margins, near coastal mountain ranges, in areas subjected to glaciation, and in regions of high relief, and coastal plains go on passive margins and in areas of low relief. These are some of their associated landforms:

Landforms associated with coast types
 Cliffs/Bluffs
 Platforms
 Coves
 Gorges
 Sea Caves/Arches/Stacks
 Uplift Terraces

Estuaries occur when river valleys flood, fjords go in mid to high latitudes where glaciers existed but do not exist now. Organic coasts are often associated with coastal plains, mangrove swamps go in the tropics, salt marshes go in the not-tropics, and of course coral reefs go offshore in the tropics. And now your world has beautiful, naturalistic shorelines! Bear in mind that this section is not exhaustive, as coastlines are insanely diverse. There is a lot of complexity that has been abstracted away for the sake of not writing a novel, so it is recommended to look into the various topographies mentioned.

### Glaciers

Glaciers are large masses of ice formed of compressed snow that move slowly under their own weight. Broadly speaking, glaciers come in two forms: continental glaciers like antarctica, and mountain glaciers like the ones in Alaska.

#### Mountain Glacier Landscapes

Mountain glaciers are comparatively small (100s m-100s km long), only occur in and around mountainous regions, and generally flow from areas of high elevation to areas of low elevation, with the terrain dictating how they do so.

The largest type of mountain glacier is the mountain ice cap or icefield. These form in any large mountain basins or atop large mountain plateaus. They are relatively flat and tend to submerge mountain peaks and ridges. Any unsubmerged peaks and ridges poking through the ice are called Nunataks. Mountain Ice Caps will be drained through gaps in the topography through a series of outlet glaciers.

Sometimes these outlet glaciers will be valley glaciers. These are mountain glaciers that flow down what was once a mountain river valley. Debris from the surrounding valley walls will accumulate at the glacier's margins, forming lateral moraines. When two or more valley glaciers merge, their lateral moraines will also merge, forming one or more medial moraines. Due to compression within the glacier, subsurface debris may be forced to the surface, forming thrust or shear moraines. Finally, end moraines form when debris carried by the glacier gets dumped at the glacier's snout.

Other accumulations of debris may also be present on the surface of a valley glacier. Lobe-shaped deposits of rockfall, dirt cones, and large boulders called erratics are among these. The surface of a valley glacier may feature deep cracks known as crevasses. These are hundreds of meters long, tens of meters deep, and many meters wide. Crevasses form when glacial ice is fast-flowing and/or flows over steps in the underlying terrain. They may be visible, or filled with snow, or debris.

Valley glaciers may terminate within the valley itself, but if it terminates in an adjacent plain, it will form a lobe-shaped structure known as a Piedmont Glacier. Alternatively a valley glacier may flow into the sea as a tidewater glacier. Icebergs form as ice calves off the end of the tidewater glacier. Mountain glacier icebergs tend to be small, irregularly shaped pinnacle bergs.

Hanging glaciers are identical to valley glaciers except they form in hanging valleys. Bits of ice can calve off the snout and fall down the mountain, often triggering avalanches. Cirque glaciers are glaciers that form in cirques, bowl-shaped depressions that are carved into the side of a mountain. If two cirque glaciers form in adjacent cirques, they will carve into the intervening terrain and produce a knife-edged ridge known as an Arête or Freaking Awesome Ridge. Any upstanding spikes are called Gendarmes, and any troughs or passes are called Cols. Lots of french around cirque glaciers.

If three or more cirque glaciers are around a peak, they will carve a pyramidal structure known as a horn. The Matterhorn is a classical example of this.

#### Continental Glacier Landscapes

Continental glaciers are massive, blanketing vast swathes of continental crust. They overwhelm the underlying topography to such an extent that their flow is entirely unconstrained by terrain. Continental glaciers that cover areas greater than 50,000 km2 are called ice sheets, and contiental glaciers that cover areas less than that are called ice caps. Both sheets and caps are dome-shaped and flow out radially from their thickest point, thinning towards their edges. Smaller local domes may be present depending on the underlying topography.

Ice streams, fast-flowing regions of the cap, will drain the glacier. They are commonly hundreds of kilometers long, less than 50 km wide, less than 2 km deep, and move at roughly a kilometer per year. Like mountain glaciers, expect lots of crevasses in the ice streams, especially near the margins of the continental glacier. Nunataks may also be present but nowhere near as frequently as in mountain ice fields. However, a large enough mountain range will probably stick up above the ice and look really stark and desolate and cool. When they do occur, expect moraines, rock falls, and erratics.

Standing in the middle of a continental glacier is really boring. It is a vast, flat white desert in all directions broken up only occasionally by some crevasses and rocky outcroppings. The margins of a continental glacier are much more interesting! If it terminates on land, it will do so via a series of lobe-shaped outlet glaciers. These act like mountain glaciers and so will manifest a lot of their features.

Strong, often hurricane-force winds will blow off the margins of a continental glacier. These *Katabatic winds* will create a sort of hazy look as snow and dust are blown off the surface into the air. They may also strip a region of its snow cover forming a Glacial Oasis, a snow and ice-free area in an otherwise ice-covered region.

If the continental glacier terminates in the sea, it will form a broad, flat ice shelf that is 100 to 1000 meters thick. Beyond the ice shelf the sea itself may freeze, forming 1-5 meter thick sea ice. Katabatic winds blowing over an ice shelf can rip apart sea ice, forming ice-free lanes known as Polynyas. Icebergs calved from ice shelves will tend to be Tabular bergs, icebergs that are many times wider than they are high.

These icebergs can be *big*. As in, ***JAMAICA*** big. Most of these icebergs will be a blue-white color, but occasionally they can be yellow (dead plankton/iron oxide rich seawater freezes onto berg), green (mixture of blue and yellow), black (pure, air bubble free ice/volcanic ash), or multicolored (seawater with specific particulate content freezes into cracks in the berg, later seawater with a different particulate content freezes into other cracks.

#### Glacial Placement

To get a complete picture of what is going on in your world, you will need to find where your glaciers are in your modern world and where they were in your world's last ice age.

Assuming your world is similar to modern day earth, your continental glaciers maybe placed 60-90º N/S in the polar ice cap climate zone. Sea ice will be present in the surrounding oceans, though coverage will vary by season. In winter, they will be present at ~70-90º N/S and at 45º N/S along coasts where cold currents flow. In the summer, this zone will be smaller, perhaps at 75/80-90º N/S, and 55-60º N/S along cold current coasts. Icebergs will go from the ice caps along your ocean currents. If you know those (see part 7), you will be able to identify any dangerous shipping routes.

Mountain glaciers can be placed in any of your mountainous regions at any latitude at high elevations. In general, mountain glaciers should not be placed in mountain rain shadows as the lack of snowfall in these regions will prevent glacial formation. The closer you get to the equator, the more your glaciers will be limited to poleward-facing slopes.

During the last ice age, assuming your world is similar to earth, place your continental glaciers between 45-90º N/S in the Polar ice cap climate zone. For mountain glaciers, place them at any latitude but this time the elevation limits are not as stringent.

Plotting both the last ice age and modern glaciers allows you to identify regions on your world that were once glaciated but currently are not, which will come in handy later.

### Post-Glacial Landforms of Mountain Glaciers

Any of the landforms mentioned previously will become more exposed and dramatic once the mountain glaciers have fully receded. Mountain ice caps will smooth and round any peaks that were submerged in the ice. Any unsubmerged peaks–Nunataks–will be made more jagged and rugged due to frost shattering.

Cirque glaciers will leave behind cirques or carries, which will often be filled with a small, moraine-dammed lake known as a tarn. Tarns may be seasonal or persistent. Various types of valley glaciers will leave behind deep glacial troughs known as U-shaped valleys. These may be hundreds of meters deep and tens of kilometers long and may be host to a wide variety of landforms.

The head will be a steep, almost sheer, rugged rocky face known as a trough end. Expect cool looking waterfalls. The floor of a U-shaped valley will for the most part be wide and flat. Where bands of soft rock are present, the valley glacier will have carved depressions into the rock tens to hundreds of meters of deep forming fjord-lakes, large lakes spanning most if not all of the valley floor, or paternoster lakes, smaller lakes that chain together like beads on a string.

Where bands of hard rock are present, valley steps will form on the valley floor. The up-ice, or stoss side of the step will be smoother and gently sloping, whereas the down-ice or lee side of the step will be steep and rugged. If a step spans the entire valley floor, it is called a riegel. Riegels may impound lakes and depending on their height may have rapids or waterfalls cascading over them.

Medial moraines, erratics, kames, and eskers may also be present on the valley floor. The remnants of the glaciers medial moraine may run as a ridge or mound of glacial debris, a till, down the center of the valley floor, though most do not survive glacial retreat. Erratics, large boulders dumped by the retreating glacier, may be randomly strewn across the valley floor. These can be anything from pebbles up to huge boulders weighing several hundred tons.

Kames are flat-topped small hills of till about 100 meters long and 10-ish meters wide. Eskers are long, winding ridges of till. In alpine regions, these can be tens of kilometers long, tens of meters wide, and over ten meters high. Kames and eskers typically occur together and are a product of glacial meltwater. Finally, a ground moraine or till sheet is a blanket of mixed till covering the valley floor. Basically, any and all material that didn't go into forming the features mentioned above gets dumped everywhere randomly, making a huge mess and forming a gently undulating landscape with low rises and ridges alternating with small depressions, kettles and kettle ponds. Kettles are small bowl-shaped depressions that form when a detached or buried bit of ice melts.

At the sides of the u-shaped valley, we can usually find the remnants of the glacier's lateral moraines. These ridges or mounts of till may be hundreds of meters high and wide, though most are way smaller than that and are prone to being eroded away over time. Alternatively, Kame terraces may be found. These are long, flat, bench-like deposits of sediment that line the valley sides. They are also a product of glacial meltwater. The walls of the valley will feaure alternating hanging valleys and truncated spurs. Truncated spurs are steep, inverted V-shaped cliffs that form when the interlocking spurs of a pre-glaciated river valley get bulldozed by the valley glacier. Hanging valleys will enter the main U-shaped valley at elevation. If it was glaciated, it will be another U-shaped valley and so will contain all the features above. Spectacular waterfalls often drain the hanging valleys into the main valley.

Near what was once the snout of the valley glacier, the remnants of the glacier's end moraine can be found as an arc-shaped deposit of glacial debris about 60 meters in height. This end moraine marks the furthest extent of the glacier so we call it a terminal moraine. A retreating glacier does not do so linearly, and may speed up, slow down, stop, or even advance depending on how hot or cold the climate at any given moment happened to be. If the glacier repeatedly halted during its retreat, there may be a series oend moraines called recessional moraines can form behind the terminal moraine. The longer the halt, the more material builds up, and the higher and larger the new end moraine will be. Expect lakes to be trapped between these structures.

Any time the glacier advanced, it would have bulldozed material at its snout, forming thick push moraines, which could make the landscape look like a rough plowed field or just increase the size of a recessional moraine. Expect the landscape here to be quite chaotic. And that is what deglaciated mountain landscapes look like.

Before we move on however, we must note that if a U-shaped valley gets partially flooded by seawater, it is called a Fjord, so expect them to be present any time you have a coastal mountain range that would once have been glaciated but currently is not. Most of them are deeper than the adjoining sea, with their terminal moraines forming a sill or shoal at their mouths. Often times, these ridges cause extreme currents, whirlpools, maelstroms, and saltwater rapids. By the way, a fully submerged U-shaped valley is called a marine trough but no one cares about those.

### Post-Glacial Landforms of Continental Glaciers

Continental glaciers blanket all topography, highlands and lowlands. The landforms left behind in the highland regions of a continental regions will be identical to those we just discussed. The post-glaciated lowland regions will differ slightly however.

A good chunk of these regions will be dominated by *knock-and-lochan topography*. These are vast, low-lying regions spanning huge areas (often several hundreds of kilometers in width). THe landscape is gently undulating, with innumerable depressions and lakes, alternating with small rocky hills and outcropping.

These rocky hills may come in many forms. Domes are rocky hills shaped like domes, less than 100 meters in size. Their surfaces are smooth. Roche Moutonnées are again small hills of solid rock less than 100 meters again. Unlike domes, they are streamlined in the direction of the ice flow. Their stoss sides are gently sloping, and their lee sides are steep, rugged, and clifflike. A medium-sized RM between 100 and a thousand meters long is called a whaleback or a rock drumlin. The largest of them, over a kilometer long, are called Flyggbergs for some reason.

Crag-and-tails are large, rugged outcroppings of resistant rock, often volcanic types, with a smooth sloping tail of till in their lees. Expect large settlements to spring up around these. The crag is easily defensible and the tail is a great location for a settlement. Edinburgh castle in scotland is built on a crag, and the city's old town is on the corresponding tail.

Various types of ground moraine may occur in post-continental glacier regions. Degeer or Washboard moraines form whenever a continental glacier met a sea or lake. They're essentially the same as recessional moraines only they're underwater. They form as a series of parallel ridges perpendicular to the direction of the ice flow. They tend to be ~5m high, 10-50m wide, and spaced ~300m apart. If the land rises or the water level drops afterwards, the De Geer moraines become exposed, forming a visually stunning landscape. An example of exposed De Geer moraines is the Kvarken Archipelago in Finland. Look it up!

Rogen moraines dominate the interior of what was the continental ice sheet. They are arc-shaped deposits of till lying perpendicular to the direction of the ice flow with their horns pointing in the down-ice direction. They often occur in close, regularly spaced groups with each individual moraine being roughly 10-30m high, 100-300m wide, and between 300-1200m in length. Lakes tend to fill the depressions between them, giving the landscape a very chaotic appearance when viewed from above. Nearby the rogen moraines and/or in close proximity to the edge of the former continental glacier is drumlin fields are often present. These are smooth hills of glacial tills, elongated in the direction of the ice flow. Their stoss sides are steep and the lee sides are gently sloping. Drumlins are typically between 250-1000m long and 120-300m wide. They tend to occur in their thosuands in groups, forming a drumlin field or drumlin swarm. Look its the shire!

Also near the margins of the continental glacier, there can be tunnel valleys. Tunnel valleys are gorges between 2 and 4 kilometers wide, over a hundred meters deep, and 30-100 km in length. They form when subglacial melt cuts into the underlying bedrock. Tunnel valleys may become filled with sediment, forming dry valleys, or with water, forming lakes similar to the Finger Lakes in western New York.

Till plains are large, flat low-lying regions that are sometimes smoothly undulating, blanketed in a thick ground moraine. Till plains can be extremely fertile farmland, so put some farmland here. Just like mountain glaciers, we can also expect eskers, kames, and erratics, expect B I G. These eskers can be hundreds of kilometers long, hundreds of meters long, and over ten meters in height.

Kames in continental glacier lowlands may occur in kame fields, giving rise to kame and kettle topography. Erratics will be utterly massive, upwards of 20,000 tons. Finally, near the end of the continental glacier, we will probably find end moraine complexes. Again, like before, but b way bigger. The terminal moraine of a continental glacier can be hundreds of kilometers long, hundreds of meters high, and kilometers wide. Put cool castles on these.

### Glaciofluvial Mountain Glacier Landforms

If your planet is like modern earth you will likely have many regions that are still partially glaciated with retreating glaciers. Retreating glaciers are melting glaciers, so expect landforms created by glacial meltwater to dominate in these regions. Meltwater flowing on the surface of a glacier will form superglacial ponds and meltwater channels. These bodies can drain through crevasses and moulins, round, near-vertical pothols in the surface of the glacier extending down to bedrock, roughly 10 meters in width. The sediment carried by the meltwater will be edeposited in these locations and will give rise to the kames mentioned previously once the glacier fully retreats.

Meltwater can also flow at the sides of a mountain glacier. Ice-marginal ponds and channels will be found here. Sediment would be deposited here, producing the Kame terraces mentioned earlier. Meltwater flowing at the base of a glacier can carve channels into the bedrock or into the ice itself. The former will produce small tunnel valleys, and the latter will produce a system of glacial caves, which will eventually be choked with sediment and become eskers.

Most meltwater will eventually make its way to the snout of the glacier. If it terminates on a plain, a system of braided meltwater rivers called an outwash plain or Sandur will form. Sediment will get sorted by the meltwater, so large debris will be found near the terminal moraine, and finer debris will be present further down the outwash plain, THere will probably also be kettle holes and lakes everywhere. If the glacier terminates in a valley, the width of the valley will become a mini-outwash plain, creating a "valley train". Lakes are common in front of glaciers. These may be moraine-dammed or dammed by the ice. If the dam breaks or the lake overtops its barrier, a glacial outburst flood occurs. These may be sporadic or seasonal and they are devastating. They can move over 300,000 cubic meters of water, 25 thousand tons of ice and another 25,000 tons of debris every second.

### Glaciofluvial Continental Glacier Landforms

The glaciofluvial landforms of retreating continental glaciers are mostly the same as those present around mountain glaciers, except massively bigger. Instead of superglacial ponds and channels, expect full-on superglacial lakes and rivers with immense meltwater waterfalls castcading into giant moulins or over the edge of the ice margin into mega pro-glacial lakes. When these lakes outbursted, they were powerful enough to entirely rework the geography of the proglacial region into *channeled scabland*. Channeled scablands are vast flat expanses deeply scarred by meltwater channels, canyons, gorges, and so on. They have poor soil and essentially no vegetation.

The glacial outbursts were so cataclysmic that they reworked the shape of the landmasses themselves. The Straits of Dover were carved out by one about 400 thousand years ago.

### Summary

For the most part, mountain and continental postglacial landforms are fairly similar, with scale being the main variable. Use the Cold climate model discussed here to find where the ice caps used to be during the last ice age. Fully glacial landscapes will go where glaciers actually are in the modern day, glaciofluvial landscapes appear on the edges, and postglacial landscapes occur where glaciers used to be but are not today.

## Uninhabitable Planets

Uninhabitable planets, being much more common and varied than habitable planets, are also very useful to map. Uninhabitable planets can generally be split into these eight categories:

* Gas Giants/Dwarfs
* Selenas/Mercurians/Cereslikes
* Venusians
* Lava Worlds
* Martians
* Iolikes
* Icy Worlds
* Exotic Worlds

### Gas Giants/Dwarfs

Gas Giants and Dwarfs are among the most common planet types, and they are very simple to map. One can simply plot out bands of varying widths, and then add randomly placed storms and other cloud features. If you wish you can put a polar hexagon on some of them, but this is not going to happen very often and the causes are unknown to scientists.

### Selenas/Mercurians/Cereslikes

Selenas and Mercurians are another common planetary type that is also simple to map. They have very different compositions, but their surfaces look very similar and are therefore lumped into one category here.

Selenas and Mercurians are distinguished by the fact that they are geologically dead and are therefore pocked with craters and cracks. Because of how crater formation works, simply place any maria that are present first, followed by increasingly smaller craters. After this is done, you may place the occasional relatively large crater somewhere on the surface and add ejecta rays streaming away from it. In the case of mercurians, follow the above minus maria. Also, add more high cliffs and cracks than before.

A rare subclass of selenas are Ceres-like worlds, which are small planets with rocky and icy surfaces, possibly with ice volcanoes and other hydrothermal activity in evidence. Oh, and salt deposits. Put those in places.

### Venusians

Venusian surfaces are characterized by having no present tectonic plates. Essentially, map them by randomly placing highlands and making everything super wrinkly, then add lots and lots of volcanic craters. As for clouds, just copy venus' texture no one's gonna notice. In all seriousness though, Venusian clouds are near-featureless, and are nowhere near as interesting to look at as in most pictures you've seen. Whatever cloudmap you have now, decontrast it by a lot.

### Lava Worlds

For worlds that are entirely covered in lava, you're already done and you don't have to actually map anything. For worlds that are only partially covered in lava, make a selena map as above, but replace the mares with actual lava. Fill any lowlands in a similar way.

### Martians

Martian worlds are defined by a lack of plate tectonics, completely dry terrain, and *evidence of past water presence*. As such, randomly place your highlands but smooth them out and place such things as eroded river paths and dry lakebeds. You may have very large volcanoes, place at will on a highland, but use sparingly. Finally, large highlands are likely to have large canyons running through them, similar to the Valles Marineris running through the Tharsis highlands. Place one of them if you like and make it look cool.

### Iolikes

Io is a unique planet, a terrestrial world under such tidal stress that its volcanoes spout plasma into space around its orbit. Planets like it are very difficult to map, as nothing should realistically stay up to date for very long. There tend to be hundreds of constant volcanoes ranging in size from the very small to the enormous, with the largest of them supporting permanent lava lakes up to 200 kilometers in diameter.

    To map a world like Io, a necessary first step is determining the tidal force relative to io itself to gauge how many and how powerful the volcanoes should be. After this, place points on your map corresponding to your largest volcanoes, as these will be functionally alone in driving the development of surface features. Impact craters will be nonexistent.

Place funky volcanic terrain ripped from Io's map at random around the map, including circles of ejecta deposits surrounding the largest active volcanoes, as shown to the right.

### Asteroids

Asteroids tend to be undifferentiated lumps of material too small to pull themselves into a spherical shape. As such, their actual form is mostly a crapshoot and you can make a pretty decent model of one by grabbing some playdoh or similar material and messing around with it until you get a nice lumpy shape that looks right.

## Conclusion

You will notice that parts of this tutorial call for things we haven't done yet. These things will be done in Worldbuilding Guide Part 7: Atmospheres & Oceans, and then we have finally finished the physical properties of our universe!