From mountains high to caverns deep. Welcome back, Outlander, for Part 2 of a 3 Part cheatsheet overview of my larger 16 entry Mythic Ecology Series, a series on how learning real-world landscape features can enrich fantasy worldbuilding and storytelling for Dungeon Masters, Game Masters, and fiction writers. This post covers landforms: forests, mountains, valleys, plains, deserts, and caves. Part 3 will cover ambience. Enjoy!
How do you use this stuff in practice? Check out the tools and tips in the “Worldbuilding” and “Mapping Tools & Guides” sections of my free D&D 5e resources compilation. These tips help flesh out details for Dice Drop Maps really well too, a popular method of rolling worlds.
What else? I also highly recommend using DonJon’s free D&D 5e Bestiary, which has all the 5e Monster Manual, Volo’s, and Mordenkainen’s monsters sortable by environment; the ones relevant to this entry include the “Desert”, “Forest”, “Grassland”, “Hill”, “Jungle”, “Mountain”, and “Underdark” habitats.
Special thanks to my Patron Adam Roder for helping make this post possible.
PART 1: FOREST WORLDBUILDING SUMMARY
NOTE: All terms covered in depth with visuals and narrative functions in my Forest Worldbuilding post.
1. Forest development mainly depends on variations of precipitation, elevation, temperature, and sunlight, as well as animal migrations, and decomposition.
Forest Formation & Ecological Succession
1. Primary succession for forests starts with grasses, herbs, ferns, and fungi (or lichens then mosses beforehand), from which shrublands develop, followed by young and small trees and vines, and then mature and large trees, eventually forming old growth with a closed canopy climax, shading out seedlings.
2. Secondary succession can occur following wildfires, floods, landslides, or blights. Some of these can create snag forests with standing limbless trees but abundant biodiversity, which contrasts against a more limited secondary growth after deforestation.
3. Forests can also shift toward swamp or savanna or desert states.
1. Trees develop hard bark exteriors, forming as annual rings of earlywood and latewood. Their main trunk (bole) supports both big branches (boughs) and twigs, plus foliage and blossoms, sometimes catkin flower clusters.
2. Trees reach into the ground with roots, the crowns of which can sometimes form lignotuber protrusions. They transport sap within themselves, and may self-repair using pitch. Hard knots can form where branches once grew, and hollow cavities form as well.
1. Fungi like yeasts, mildews, molds, and mushrooms decompose detritus in woodlands, sometimes in fairy ring formations, or as polypores fruiting on trees.
2. Vines climb, whereas underground stems like bulbs, corms, rhizomes, and tubers burrow.
3. Forbs, herbs other than grasses, sedges, and rushes, flesh out the ground layers of forests.
Basic Tree Categories
1. Deciduous trees shed their leaves annually, whereas evergreen shed theirs gradually or stay green year-round. Deciduous most often appear as hard wood with broad leaves, whereas evergreen most often appear as conifers: soft wood with needles or scales and cone-like fruit. Rare deciduous conifers also exist.
1. The Forest Floor contains decomposing leaves and needles, animal droppings, and fallen trees, and this decay becomes soil. Dense canopies above can reduce sunlight and thus vegetation here, unless near water or clearings. Above this, young trees, bushes, shrubs, snags, and leafy herbs comprise the Understory Layer, relatively open but dark. Waterways or clearings can become thickets.
3. The majority of biodiversity resides in the Canopy Layer, marked by tall tees and overlapping treetop connected by ranches, twigs, leaves, vines, mosses, and lichens. Above this, the Emergent Layer features giant crowned trees in higher sunlight, temperature, and winds.
Tree Group Terms
1. Groups of similar trees appear as stands. Hammocks refer to islands of trees contrasting with nearby ecosystems, whereas dense stands become thickets.
2. Without much undergrowth, groves form, and trees cut down to stools then regrown create multiple, smaller shoots (copses).
1. Tropical forests have wet and dry seasons, with overall consistent sunlight and temperature, and abundant rainfall, including through monsoon seasons. Little fertile soil but high biodiversity.
2. Year-round rain shape tropical evergreen rainforests, whereas short dry seasons shape tropical and subtropical moist broadleaf forests, and longer dry seasons shape tropical and subtropical dry broadleaf and coniferous forests.
3. Montane and laurel forests get water mostly from mist or fog at high elevation, whereas flooded forests arise as submerged swamp.
1. Temperate Forests have Spring, Summer, Fall, and Winter seasons.
2. Mild wet winters and dry summers shape moist coniferous and evergreen broadleaf forests. At higher elevations, dry coniferous forests form.
3. Temperate broadleaf rainforest have mild winters and consistent rain, whereas Mediterranean forests have dry summers and rainy winters; both evergreen.
1. Boreal forests (taiga) have a mild Summer and a long Winter season.
2. Southernmost taiga have dense trees with mossy groundcover, whereas northernmost taiga have sparse and stunted trees with lichen groundcover.
1. Low-density forests with much open habitat and sunlight manifest as woodlands, which can mix with grasslands to become savanna.
2. Dry transitional forests can appear as heat-tolerant, hard-leaved sclerophyllous, or as thorn forests, which can turn into savanna or desert. Wet ones can arise as mangroves: coastal swamps.
1. Rarer forests can manifest with massive swollen trunks (baobob) or tall skinny trunks (bamboo), or with upturned crowns (dragon’s blood). And they can even have thorny bark (kapok), or fruiting bark (grapetree), or colorful bark (rainbow eucalyptus).
2. They can also have dense overgrowth (jungle) or overruns (spider trees). Finally, they can have massive size (redwood and tetrameles).
Deformation & Damages
1. Trees can have abnormal growths like burls or galls or witch’s brooms above, or geoxyles at root. Dead and dying trees become snags.
2. Frost heaving can cause tilted or crooked trees. Wind can cause windsnap at trunk or windthrow uprooting.
1. Earlywood in Spring has lighter color, more softness and porosity, whereas latewood in Summer has the opposite.
2. The central heartwood of trees has a darker, dense, and dead core providing strength, whereas the outer sapwood has a lighter, looser, living bands transporting nutrients.
PART 2: MOUNTAIN WOLRDBUILDING SUMMARY
1. Mountains evolve through tectonic forces or volcanism raising surfaces, or else rivers, weather, and glaciers eroding surfaces. These can create both isolated summits and whole mountain ranges. Typically, upland regions hold cooler and drier climates.
Mountain Formation & Ecological Succession
1. Primary ecological succession on mountains requires species tolerant of higher elevation, and often heavy winds. Due to precipitation, humidity, and soil development patterns here, vegetation zones on mountains can appear somewhat upside-down compared to normal forest succession, with bands of tall trees residing at the lower elevation, shrublands at the middle elevation, and grasslands, mosses, forbs, and lichens above, with caps of barren rock. By exception, for mountainous tropical rainforests, higher elevation often supports more biodiversity.
2. Mountains’ stark altitudinal contrasts can create localized and isolated “sky island” habitats, with little upward migration. Climaxes however often lead to montane forests of conifers, up to the tree line, above which trees cannot thrive, and alpine habitats of grasslands instead form.
3. Secondary succession can occur after rockfalls, avalanches, mudslides, and the like, once sunny groves emerge.
1. “Mountain” denotes a large landform rising steeply above surrounding land, bigger than a hill.
2. Crust faults from lifting or tilting form block mountains; more severe action, from tectonic plates, can form fold mountains. In contrast, volcanic action can create domes or volcanos. And erosion can create plateau mountains.
Special Mountain Terrain
1. In dry regions, steep, bare slopes can manifest as badlands; flash floods in their basins can create fan-shaped sediment deposits (bajada).
2. Mountain ranges refer to clusters of similar mountains, whereas sky islands refer to isolated mountains contrasting with their surroundings.
3. Shield volcanoes denote low profile volcanoes, whereas stratovolcanoes refer to tall, conical ones, tuya to flat-topped, steep-sided volcanoes, and somma volcanos to partially filled calderas with a central cone.
Ridges & Terraces
1. Ridges refer to chains of mountains or hills forming a continuous elevated crest. This includes from converging glacial erosion – ridges atop valleys (arete); from frost and wind tear – steep, rocky, rough, and bare slopes (bratschen); gentle slopes beside steep slopes (cuesta and fault scarp and homoclinal ridges); from erosion – steep, triangular flatirons and prominent hills of windblown sediment (paha ridges); steep and symmetrical hogbacks; and ones descending toward valley floors or coastlines, cut short (truncated spurs).
2. Terraces refer to flat or gently-sloping, step-like landforms bounded by a steeper slope, usually in series. This includes the step-like monoclines; arch-like folds (anticlines); downward folds (synclines); from soil waterlogging and drying – terracettes.
Peaks & Passes
1. Mountain tops and ledges can bear cliffs, with steep drop-offs.
2. Mountain tops can also have towering pinnacle shafts. Divergent glacial erosion can create pyramidal peaks. Their highest points form summits, sometimes double summits.
2. Difficult low points (cols) and drainage ridges (saddles) separate mountain peaks, sometimes forming navigable passes.
3. Lava can form protrusive monoliths like lava spines and batholiths.
1. A “hill” denotes a landform extending above surrounding terrain, but smaller than a mountain. Includes smaller “hillocks”. Hills have hillsides, some of which can become transitional foothills between lowlands and highlands (and more rarely, thrustfold belts). “Rolling hills” refer to groups of low hills.
2. Erosion in arid regions can create specific hill forms, including steep residual hills (mogote) and gentler residual hills (nubbins). A butte refers to a hill taller than its width, with steep sides and flattish tops. Mesas refer to larger ones wider than tall, and plateaus to even larger ones, arising from tectonics, volcanism, or erosion.
3. Volcanism can create many hill forms: conical pyroclastic fragments around volcanic vents (cinder cones, splatter cones, tuff cones), conical hills (including overgrown puy), circular lava protrusions (cryptodomes, lava domes, hornitos), and hardened magma objects within an active vent (volcanic plugs).
4. Isolated hills include inselbergs arising abruptly from flattish surrounding plains, and bornhardt dome outcroppings. Glacial or ice sheet motion over hard rock can create isolated, rocky hills (crags), often with a fan, ridge, or ramp as a tail. Glacial action can also create elongated hills (drumlin), or pingo mounds where earth covers ice.
5. Large, freestanding rock outcrops (tor) sit on smooth and gentle slopes of rounded hills like kuppe.
1. High and barren landscapes can manifest as fell, either mountain ranges or moor hills.
2. Mesas and plateaus may have some vegetation. Where tundra retreats, upland flatlands with more vegetation can support grasslands, savannas, and shrublands, as well as low-lying wetlands.
3. Erosion creates dissected plateaus with sharp reliefs; this can include potrero, where a long mesa slopes up to highlands, like a mountain flank. In contrast, sandstone specifically can isolate away a tabletop highlands (tepui).
1. Frost weathering can create blockfields of overgrown boulders. Along alpine or tundra slopes, freeze and thaw cycles combining with wind can support fellfield rock deposit habitats.
2. Hillslope washes move unconsolidated sediment of silt and rock fragments (colluvium) downhill. Similarly, glacial melt can accumulate sand, gravel, and till into mounds within depressions in retreating glaciers (kame).
3. From steep rockfaces, pebble to plate-sized rockfall can accumulate downhill as scree.
NOTE: All terms covered in depth with visuals and narrative functions in my Mountain Worldbuilding post.
PART 3: VALLEY WORLDBUILDING SUMMARY
1. As lowlands, valleys develop in tandem with their neighboring highlands: mountains and hills. The latter may direct water flow toward or away, creating rivers or lakes or deserts among the valleys. River erosion creates many valley features. Glacial and tectonic action also play key roles in shaping them.
Valley Formation & Ecological Succession
1. Valleys typically stay at a relative equilibrium in a grassland and partial shrubland stage, punctuated by some tree cover, but overall emphasizing short, annual plants like wildflowers, as seen in plains. Frequent flooding and brush fires reset the progression.
1. Linear lowlands between highlands or mountain ranges can manifest as ramp valleys with steep, ramp-like sides with flat, debris-covered floors, or as rift valleys, created by tectonic rifts or faults.
1. Valley head refers to the uppermost part of a valley. Crystalline rock valleys can also sustain bogs or alpine meadows, while limestone valleys bear rock and gravel, and previously glacial ones may develop lakes. High valley more broadly refers to a valley in the upper third of a mountain range.
1. Hanging valleys function as tributaries between a higher and lower valley. Similarly, side valleys hold tributary brooks or rivers to a larger river.
1. Streams of flowing ice confined within steep-walled valleys, or outlets of ice fields or sheets, can create valley glaciers.
2. Glacial action can lead to asymmetric valleys with steeper slopes on the sun-facing side, or bowl-shaped cirque glacier valleys on mountainsides. Valley sides display trimlines showing the recent glacial high.
3. Glacial action can also create broad meltwater valleys flowing parallel to ice margins after an Ice Age, or U-shaped tunnel valleys cut by water under glacial ice near ice sheet margins, sometimes with waterfalls. U-shaped valleys often have steps, with abrupt slope changes.
4. Erosion from glacial outflow can create box canyons, with steep walls on three sides. In valleys on permeable rock like limestone, chalk, or sandy terrain, this water sinks into bedrock, forming dry valleys.
1. Gradual erosion from rivers can create small but deep valleys called ravines, bounded by steep slopes and cliffs and often featuring steams. Broader ones become canyons (gorges), which can form defile as they create mountain passes. Dry but floodable riverbeds appear as wadi.
2. Where the river flows to the sea, steep coastal gorges (chines) can form through soft cliffs of sandstone or clay. Other permeable rock landscapes can form deep, narrow, and flat-bottomed steephead valleys, with abrupt ends. Flat-bottomed valleys can also manifest as low areas between hills (vales) or as strath, both wide and shallow.
3. Small ditches can form dell, secluded hollows in grassy or woody valleys. Large ditches or small valleys carrying water on hillsides become gullies, and larger ones become v-shaped gulches. Ones more narrow and steep, on mountains, become couloir, and teardrop-shaped hillside ones become lavaka.
4. Narrow and deep valleys with gentle slopes on concave sides manifest as glens; deep enough valleys can form draws, with parallel ridges or spurs overlooking. Longitudinal valleys refer to elongated valleys between parallel mountain chains, whereas transverse valleys refer to ones which cut at right angles across a ridge, or roughly right angles to a mountain chain or crest.
NOTE: All terms covered in depth with visuals and narrative functions in my Valley Worldbuilding post.
PART 4: PLAINS WORLDBUILDING SUMMARY
1. Plains cycles largely revolve around migratory grazing animals, flooding and drought and wildfires. Similar to valleys (which largely feature plains habitat), water flow can shift plains toward forming river or lake or desert habitats.
Plains Formation & Ecological Succession
1. Plains often arise as river floodplains or wetlands or lakes dry out and grazing animals move in, as forests die down, or as deserts grow wetter. Similar to valleys, plains stay at a relative equilibrium in a grassland and partial shrubland stage, punctuated by some tree cover, but overall emphasizing short, annual plants like wildflowers.
2. Frequent flooding and brush fires reset the progression, and grazing animals keep things from progressing toward thicker woodlands. Instead, prairies may develop deep roots.
Temperate Grasslands, Savannas, and Shrublands / Prairie / Pampas / Veld
1. Temperate grasslands includes regional terms like prairie, pampas, veld, and sometimes steppe. The primary divisions include the dry shortgrass prairie in semi-arid environments, mesic prairies with mainly forbs like wildflowers in areas with moderate rainfall, and tallgrass prairies in areas with higher rainfall and rich soils.
Tropical and Subtropical Grassland, Savannas, and Shrublands
1. In tropical climates, where semi-arid to semi-humid conditions predominate, grasslands featuring grasses and herbaceous plants, savannas featuring mixed grasslands and sparse woodlands, as well as shrublands featuring woody and herbaceous shrubs can all exist.
1. In Mediterranean climates, where dry summers and rainy winters occur, the lowland locations have mild to cool winters but inland and highland spots have colder ones.
2. This can manifest as shrubland or heathland featuring hard-leafed evergreens (chaparral). It can also appear with low, creeping dwarf-shrubs, whether as low, soft-leaved scrubland with limestone soils (garrigue) or as shrubland with dense evergreen shrubs (macchia). Or finally, as a plain of shrubland, thicket, and bushes (matorral).
1. In semi-arid or continental climates featuring grasslands and shrublands, extreme temperature variations across both season and time of day can occur. Sometimes these manifest as transition zones between Mediterranean climates and true deserts, or under the rain shadow effect of mountains.
2. Steppe can appear in specific forms. Dry grasslands in alpine regions have year-round frost despite high sunshine. Shrub-steppes have low rainfall and serve as a patchwork for perennial grasses or shrubs adapted to wildfire. The driest Mediterranean areas become subtropical steppe, whereas the more humid continental climates sustain temperate steppe.
Desert & Xeric Shrublands
1. In arid regions with extreme temperature swings across both season and time of day, desert shrublands with year-round heat, as well as divergent desert shrublands with both harsh heat and harsh winter cold can exist.
1. Dry meadows manifest as open fields with grass or other non-woody plants. This includes tundra grasslands at high elevations above the treeline (alpine meadows), coastal prairies, and desert meadows such as with desert wildflower blooms.
Wet Meadows + Flooded Grasslands & Savannas
1. Wet meadows manifest as expanses or complexes of flooded grasslands, or as grassy wetlands.
2. This includes seasonally-flooded grasslands in river floodplains (callows and floodmeadows). Floodplains exist beside periodically flooding streams or rivers enclosed by valley walls.
3. Marshes fluctuating between brief inundation and longer saturation become wet-meadows with sedges, rushes, and grasses, such as wet prairie, wet savanna, and cienega.
1. In highlands, special shrubland habitats around free-draining infertile, acidic soils (heath) can form, with open, low-growing woody vegetation. The highland form manifests as moorlands, with cooler and damper climates.
2. Highland grasslands and shrublands can also exist in montane regions. Another form includes potrero, a long, overgrown mesa sloping upward at a mountain flank.
1. In lowlands, fertile grassy plains manifest as machair. At the linear conjunctions of highlands or mountain ranges and lowlands, grassy rift valleys can form.
1. Some other variations of plains include coastal shrublands, as well as shrub swamps as transitions between swamps and wet meadows or fen.
2. Mammoth steppe refers to specific Ice Age climates along grasslands and shrublands featuring grazing megafauna. Over time, glacial action can dissolve soluble rock like limestone on flat plains until underground sinkhole and cave systems form (polje).
NOTE: All terms covered in depth with visuals and narrative functions in my Plains Worldbuilding post.
PART 5: DESERT WORLDBUILDING SUMMARY
1. Desert behavior can vary by latitude: trade wind deserts at the equator have dry winds dissipating cloud cover, mid-latitude deserts arise along interior drainage basins far from oceans, montane deserts form in arid regions of high latitude, and polar deserts remain ice-free from strong downhill mountain winds.
2. The tall mountains of rain shadow deserts prevent cloud moisture from reaching adjacent lowlands. Slightly more moisture may reach coastal deserts in the tropics, mainly in the form of winter fog.
3. Deserts can also vary by time: monsoon deserts have seasonally reversing wind and rain patterns; the inland areas may receive little of the monsoon’s precipitation, but some does collect in seasonal lakes. Finally, paleodeserts refer to former desert areas currently in non-arid states.
1. Desert cycles largely center around water scarcity, with seasonal rains and winds affecting availability. Weathering from daytime and nighttime temperature swings over time, as well as rain on hot stone, shapes many rock surfaces into broken down mosaics. Deserts may arise from denudation, with previously thick vegetation stripped away. Due to temperature, in many deserts animals only come out at dawn and dusk, or at night.
Desert Formation & Ecological Succession
1. Ecological succession in desert habitats displays dryland progression traits, including either primarily rock-based or sand-based pathways. Starting from bare rock, algal or fungal spores or bugs invade the rocks and eventually lichen can develop. The specialized lichens retain water in harsh environments and accumulate dust, forming a proto-soil. From this foundation, moss and herbs and shrubs and trees can all arise, sometimes anchoring dunes.
2. Sand-based progressions works similarly, but with more salt-tolerant species and dune microhabitats along the way.
1. Wind action on sand can create many stable dune structures of sand, silt, clay, or gypsum. Crescent- and U-shaped ones include barchans with horns pointing away from the wind and anchored by shrubs or rock (and by contrast, parabolic dunes with horns pointing into the wind), as well as lunettes deposited on the convex side of a dune. Shrubs can also serve as anchors for coppice dunes, which arise around desert vegetation.
2. At a sand sea’s far upwind margins, some dunes form as ovalar or circular dome mounds. By contrast, along seacoasts or where similar crosswinds converge, can form long, straight or slightly wave line-shaped dunes, sometimes in parallel.
3. Dunes can relate to wind in complicated ways: transverse dunes lay perpendicular to wind direction, and reversing dunes with faces temporarily in opposing directions from periodically switching winds.
4. Dunes can also aggregate: stacked ones of differing types (complex dunes), and stacked ones of similar types (compound dunes). Lithified dunes arise as sandstone compacts and hardens from sand dunes, sometimes piling into cross-hatching patterned stacks. The largest and highest form as star dunes, with crests approaching a central point.
Larger Desert Landforms
1. Rocky desert landscapes can manifest as steep badlands, colorful but barren, or as coalescing alluvial fans along a mountain front (bajada) forming as deposits of sediment from flash floods in dry basins and playa lakes. They can also arise as high, rocky, barren plateaus where wind has removed all the sand (hamada), leaving behind stony plains and depressions of interlocking gravel (desert pavement) or desert varnish rock surfaces.
2. Sandy desert landscapes can manifest as vast, dune-topped sand seas (erg) with shifting sands, as flatter sand sheets with winds too weak to form dunes, or as frequently burning sandhills.
Watersources, Extant & Extinct
1. Many possible desert water courses and basins fill only after rains, potentially causing flash floods. These include such landforms as aboveground arroyos and shallow vlei lakes and wadi river valleys, or underground dryland channels.
2. Other ephemeral water sources include dew puddles from nighttime dew, and playa lakes wet in especially wet years only. Water sources may become extinct dry lakes, such as alkali or salt flats and pans.
3. Slightly more enduring desert water courses and basins include guelta drainage channels, isolated oasis, and watering holes. Often these serve as gathering points for animals.
1. Deserts can have special holes, such as sandy depressions (blowouts) caused by wind removing sediment or soil, or decomposition chimneys forming where trees rot away after being covered by sand dunes.
2. Deserts may display unusual visual or auditory phenomena, such as mirage optical illusions, singing sands, or sailing stones.
3. Deserts sometimes bear special storms, such as sandstorms, dust storms, or the more severe haboob.
NOTE: All terms covered in depth with visuals and narrative functions in my Desert Worldbuilding post.
PART 6: CAVES WORLDBUILDING SUMMARY
1. “Cave” refers to a natural underground space large enough for a person to enter, and caverns their cave chambers. “Grotto” refers specifically to an inhabitable one, near water.
Cave Formation & Ecological Succession
1. Caves develop largely via gradual erosion by water, and bedrock collapses, such as from chemical, tectonic, or volcanic action. Gradual processes can create passages, obstructions, or crystalline structures.
2. Caves typically reach much more stable equilibrium than other habitats, due to isolation from most disturbances and temperature swings, as well as the high rate of primary producers, including those subsisting off of chemical and mineral interactions instead of sunlight.
3. Nevertheless, cave moisture sustains a foundation of mosses, ferns, liverworts, and fungi, as well as migratory and colonizing fauna. Succession can center around different states arising based on the accumulation of nitrogen via guano, by water flooding, and by air chemical composition changes.
1. Caves have distinct sections: the Entrance Zone interacts with surface soils through cracks and rock seems, groundwater seepage, and root protrusions, which extends toward the Twilight Zone, a threshold portion near cave mouths which reaches the last penetration of sunlight. The progression goes from cool, shaded, and lit, to cool, damp, and dim, then dark.
2. Beyond this exists the Dark Zone, which can still have regular contact with the surface via wind and underground streams or animal migration, or be almost entirely isolated. The farthest reaches become the Underdark Zone, with unique ecologies where primary energy comes from chemicals harvested by bacteria from minerals, rather than from sunlight.
3. Unique cave species adaptations include features like loss of pigment or eyes, elongation of limbs, and certain enhanced senses.
Cave Form Categories
1. Caves can come in simple forms, such as small and shallow rock shelters wider than deep, produced by bedrock erosion in insoluble rock, or as openings among random heaps of large fallen boulders (talus caves) at the base of cliffs.
2. In coastal mixtures of freshwater and saline, underwater (anchialine) caves can form. Wave action can also create sea caves along active or remnant coasts.
3. Water and wind erosion can create corrasional caves, where streamflow carries rock and sediment along a fault or joint. These can expand small openings from solutional processes, processes which can form solutional caves where in soluble rocks, natural groundwater acids seep through and dissolve open cracks. And where soluble minerals dissolve away, fractures and collapses of stone blocks can create fracture caves.
4. Primary caves form from the same surrounding rock type, including lava, blister, tufa, and reef cave types. Similarly, glacial caves arise as hollows within glaciers.
Cave Passage Patterns I
1. Cave passages have varying functional patterns. Along one bed or structure, braided anastomotic passages can form. Other convergences, branchwork passages, meet downstream as tributaries.
2. Pit cave passages function as vertical shafts. The more complex angular network passages appear as sequences of straight and narrow lines persisting in widespread loops.
3. The most complex and three-dimensional passages manifest through chemical action as randomized rooms formed as rising water chemically erodes rock (ramiform caves), or in a sponge-like pattern arising from solution cavities.
Cave Passage Patterns II
1. Cave passages work differently near underground water, where features like submerged passages (sumps) exist. As water swirls under extreme pressures, it can create vertical tubes in cave ceilings (avens). This water can also dissolve rock to create wide and low spaces with smooth ceilings and floors (soluble beds).
2. Cave drain complexes form from free-flowing water, creating channels like narrow keyhole passages and drain shafts, sometimes collapsing ceilings to create vault-like breakout chambers.
3. Transitional floodwater zones in caves have times of higher water and lower water; these sequences can create intertidal passages.
4. Seismic activity, pressure, and slow erosion can create passages with large stretches of hanging walls of split rock (fault-formed passages), or the straight, narrow, and deep fissure or rift passages, where rock splits or cracks widen along a joint.
1. Gradual mineral development into deposits can form whitish or translucent speleothem structures. Dripstone forms include descending stalactites, ascending stalagmites, and stalagnate columns, which form when stalactites and stalagmites meet to form pillars, or stalactites reach the cave floor.
2. Stalactites appear as conical pendants growing down from cave ceilings. These can sometimes manifest in a manner resembling chandeliers, various spirals and ribbons and curls (helictites), or elongated cylinders (soda straws).
3. Stalagmites appear as the upward protrusion counterparts to stalactites, often blunt mounds. These can sometimes manifest as tall and spindly broomstick shapes, forms resembling fried eggs, or even totem pole shapes.
1. Cave floors and walls can feature sheet-like structures called flowstones. These can manifest as wavy sheets of hanging rods resembling curtains (draperies), as mineral barriers occuring at stream ripples (rimstone dams), or even as stone waterfall formations.
1. Caves can also feature crystalline structures. This can appear as flower-like clusters (anthrodites), as loose grains of crystal (cryogenic calcite), as large crystals near seasonal pools (dogtooth spar), as needle-like growths (frostwork), or as a white, creamy substance (moonmilk).
Speleogens & Exotics
1. As cave bedrock erodes, colorful structures called speleogens can form. This can manifest as intricate mazes full of holes (boneyard), as preferentially-eroded calcite veins (boxwork), as soft rock pillars, or as small, asymmetrical, scoop-like depressions (scallops).
2. More rare variations include thin accumulations of calcite on cave pool surfaces (calcite rafts), and small cave pearl spheres arising as water drops high above. And also, small, knobby clusters (cave popcorn), submerged bell-shapes (hells bells), or even sulfur-oxidizing bacteria colonies resembling rusty snot (snottites).
Pits & Shafts
1. Caves can have many depressions, hollows, and shafts, particularly from water interactions. Along sea cliffs or coastal terraces, these can manifest as blowholes spraying jets of water from rock crevices. Along glaciers or ice sheets, surface water can flow into circular and vertical well-like shafts (moulin).
2. Bedrock collapses can also give rise to various forms: pits of exposed groundwater (cenote), deep sinkholes above a void (foiba), or depressions or holes in the ground (sinkholes).
3. Simple instances include the unroofed portions of caverns revealing subterranean rivers (karst fenster), or shallow depressions eroded into flat or gently sloping rock (panholes). More sophisticated networks of pits and shafts include the deep vertical shafts in karst terrain (abime), and features ranging from amorphous shallow pits to irregular labyrinthine hollows (scowle).
Special Cave Features
1. Caves can have special obstacles. This includes collections of large rocks or rubble obstructing cave passages (boulder chokes), partial or total collapses of cave structures creating blockages (cave ins).
2. By contrast, caves can also let in the outside, whether holes in a cave roof letting in sunlight and air (sunholes), subterranean tunnels acting as passageways, or subterranean waterfalls along vertical drop-offs.
- NOTE: All terms covered in depth with visuals and narrative functions in my Caves Worldbuilding Post.
I look forward to continuing this summary series, and I have some greater ambitions for developing Mythic Ecology into worldbuilding web tools. Give this a share if you liked it, and let me know in the comments if you have any feedback. I publish new posts on alternating Tuesdays. In the meantime, I post D&D memes and writing updates over on my site’s Facebook Page. Also, if you want to keep up-to-date on all my posts, check out my Newsletter Sign-Up to receive email notifications when I release new posts. A big thanks as always to my Patrons on Patreon, helping keep this project going: Adam, Alexander, Benjamin, Chris, Eric & Jones, Evan, Geoff, Jason, KRR, Rudy, and Tom. Thanks for your support!