Aer Canyon Pit

Geography

The Aer Canyon Pit is a vast and utterly abyssal system of canyons and ravines plunging thousands of miles below the continental plateau of the Twilight Age world. In direct opposition to the exposure, wind-blasted peaks of the Aeni Mountains or the burning sun-scoured deserts of the Adisay Outback, the pit is about depth-absolute, crushing depth, and the total suffocating intimacy of subterranean collapse. This region is an overwhelming, impossible, layered structure of abyssal terraces and vertical sink walls that descends thousands of miles into the earth to create an entirely isolated underground world where climate and air pressure-and indeed, much geology-are wildly different from those of the surface above.

Topography & Geology

The gigantic rift was formed by the convergence of ancient faulting of tectonic origin and massive, localized subsidence of the continental crust. Over vast geological time scale portions of the plateau dropped in and around these faults, creating a nested maze of gigantic sink holes and vast abyssal terraced levels connected by vertical shaft like sink-holes and great erosion chasms caused by ancient underground rivers. The canyon's topography is highly vertical and intensely unstable; the rimlands are comprised of jagged, disintegrating stone shelves that offer dizzying views of the black, sheer void.

Below this broken and fractured perimeter rim, the canyon extends through successive layers of tiered terraces of loose, crumbling rock ledges, shattered cavern roofs and delicate, natural rock bridges of stone. Beneath each tier are immense talus slopes of broken rock and collapsing scree fields that are the constant, direct result of the violent and unending cascade of rock falling from the terraces high above. Geologically, the pit is an immensely vertical slice through the entirety of the continental crust, laying bare and exposed billions of years of stratified history hidden away deep within the earth.

Each vertical cliff face presents distinct, multi-age layers of sedimentary rock interspersed with seams of incredibly dense, igneous basalt intrusions and gleaming, sparkling mineral deposits. Bright, rich iron oxide streaks paint vivid rust red bands across many layers that are dramatically at odds with layers of pale limestone, bright crystalline deposits, and vast sheets of glassy, pitch black basalt. The very bottom of the pit moves away from being a true canyon floor and into the world of the subterranean.

A maze of immense, spherical sink caves, deep cavern networks and profoundly deep, dark fissures delving into the yet uncharted continent below.

Climate & Hydrography

The climate inside the Aer Canyon Pit is a dramatic reversal of what one finds on the surface and is determined almost entirely by the vertical location and relative confinement of the pit. Although the upper rimlands above are subject to intense wind storms and are extremely arid with wide daily temperature extremes, the abyssal chambers of the canyon are relatively insulated. The overwhelming bulk of the canyon walls completely shield the depths of the pit from solar radiation and keep it locked at a cool, extremely humid, hyper-stable thermal temperature.

The density and extreme heaviness of the atmosphere trap it below the high walls, acting as a sponge: thick, dark, pervasive fog saturates the abyssal tiers and makes visibility only a matter of meters. Hydrologically the pit is the source of a huge, subterranean drainage system preserving the remnant of a massive underground river system from a bygone era. While the upper terraces are virtually arid, the seepage of water from mineral-rich rock increases dramatically at higher depths.

This weeping moisture nourishes clinging moss gardens and forms deep cold condensation pools. The floor of the pit is traversed by slow-moving, underground rivers and geothermally heated mineral springs, and the bottom-most caverns contain enormous subterranean lakes. While the subterranean hydrology remains surprisingly constant throughout most of the year it is also susceptible to dramatic changes: during heavy surface storms flash floodwaters course into the canyon through the numerous peripheral ravines and vertical drop shafts, creating a raging and destructive river of mud, rock and water.

Traversability

Traversing the Aer Canyon Pit is exceptionally exhausting and perilous task which can be accomplished only through specialized, extreme mountaineering tactics. The terrain is inherently unfriendly and is characterized by shifting, wet rock, crumbling limestone ledges, and frequent and imminent structural failures caused by falling rock from higher levels. The verticality and structure of the canyon make overland travel impossible, and exploration must rely on techniques designed to traverse thousands of feet vertically rather than miles horizontally.

Visibility at lower levels is almost zero without external light sources, due to perpetual fog and utter blackness, and navigation of the impossibly convoluted maze of caves can quickly become impossible without highly advanced equipment or innate navigational skill. Many of the deeper sink holes are completely unreachable for practical reasons: access is limited by massive, impassable walls of collapsed rock debris, plunging waterfalls or entire submerged cave systems that have never seen the light of day.

Plants

Rimland Flora (Upper Canyon Xerophytes)

The Aer Canyon Pit's flora is completely dictated by the brutal vertical stratification. Depth, diminished light and geology create completely different life forms in the canyon pit as one continues to fall. The high-angled, barren slopes of the rimlands are dominated by sparse and extremely exposed xerophytic (arid-loving) vegetation in the form of low scrub, grasses and woody shrubs. In order to combat the high levels of solar radiation and winds these rimland plants exhibit narrow, needle-like foliage and possess high waxy cuticles to reflect thermal energy.

Without topsoil for these plants, deep roots that burrow down into the cracks in the rocky cliffs seek out tiny veins of groundwater deep within the rock in order to survive the intense wind.

Cliff-Wall Flora (Lithophytes and Hanging Gardens)

As one falls over the edge, the high, vertical cliff walls are home to gravity-defying populations of lithophytic (rock-dwelling) vegetation that colonize small fissures, erosion shelves and drip-holes and that possess the characteristics of having shallow, wide-reaching roots that stick tightly to the bare rock walls. In the middle levels where condensation trapped by the cliff walls is constantly falling down, the flora becomes thick with trailing roots and vines that absorb water right out of the damp fog, hanging down the faces of the cliffs.

But these high walls also have numerous extreme microclimates; a sun-soaked cliff face will have none of these organisms, whereas a shaded overhang a few meters away from it could be teeming with moss and pale ferns that depend on water. These ecosystems are routinely cleared from the cliff faces by falling debris and so their survival depends on the rate at which they grow vegetation once more on the newly barren rock face.

Abyssal Basin Flora (Sciophytes and Subterranean Fungi)

The final layers of the Aer canyon pit are not traditional plant ecosystems. In the absolute dark of the deep, the abyssal pits are filled with the dark, damp, humid air that creates a completely alien, separated ecosystem. The bottom is covered with sciophytes (shade-loving flora) such as delicate thin grasses, and large-leaved low growing plants that spread their surfaces widely out to catch any light that might filter down to them from many kilometers away.

Where light completely vanishes within the abyssal caverns, the entire environment shifts completely to subterranean fungus, as well as pale underground flora, living exclusively off of the dripping mineral water, underground upwellings, and decomposition of organic material that fell down from the upper levels of the canyon over millennia.

Seasonal Adaptations (Vertical Stratification)

While not truly seasonal, plants within the Aer Canyon Pit exist based on static vertical stratigraphy rather than cyclic changes as in the rest of the world during the Twilight Age. The vertical gradient of this world is entirely controlled by depth; the outer rimlands call for defense from heat and sun while the abyss calls for extremely efficient growth for plants struggling to gain light and a reliance on fungi and chemisynthesis for those living in absolute darkness.

Every ecosystem of the Aer Canyon Pit exists based on being constantly devastated by natural disasters such as rockfalls and flood and that the only thing that allows these organisms to survive is the ability to immediately creep back up the freshly barren walls.

Animals

Rimland Fauna (Upper Canyon Edge-Dwellers)

The animals that inhabit the Aer Canyon Pit are adapted to life on a knife's edge of extreme vertical isolation, fragmentation, and an impossibly dizzying fall into the abyss. They are completely different from the plains-roaming, cursorial animals of Adisay. The creatures of the rimlands are hard, agile, and suited to broken rock and crumbly ledges. Their survival from the dizzying height depends upon highly developed spatial perception, acute sense of balance, and strong, light frames with hooked claws and wide, gripping pads.

Predators along the rim use the environment to their advantage.Apex predatorsclaim territories around natural choke points-narrow stone bridges, fallen ledges, ravines. They never chase down prey, and are strictly ambush hunters that use the poor visibility and vertical complexity of the canyon rim to corner their victims against the drop. Since water is cripplingly scarce on the rimlands, the resident animal populations are highly migratory and undertake perilous, vertical migrations down to the deep weep-holes and seeps of the abyss during harsh droughts.

Cliff-Wall Fauna (Lithic Ecosystems)

Further down, past the rim, the sheer canyon walls support entirely vertical communities of saxicolous animals: creatures that are well adapted to life on vertical rock. They have dorso-ventrally flattened (pancake-like) bodies, and heavily articulated, reinforced gripping appendages that allow them to grip to the naked stone surface and climb even narrow fissures. Cryptic coloration is crucial on the wall; many animals can camouflage seamlessly with the rocky surface. Irregular bands, muddled color patterns that mimic the local rock strata and shifting shadows.

Many of these cliff-dwellers spend their entire lives wedged deep within cracks, shielded from falling rock and rimland predators. Fungal grazers and scavengers can be seen tightly aggregated around individual seep-fed ledges; they migrate up and down the vertical wall as temperature and humidity fluctuate during the year.

Abyssal Fauna (Troglobitic and Deep-Basin Species)

In the crushing, everlasting dark of the deep abyssal basins, an alien world can be found. These deep-Basin creatures, totally isolated by kilometers of rock from the upper world, are adapted for the extremely humid, low-energy conditions. These deep-Basin environments are dominated by true troglobitic creatures (cave-dwelling organisms). There are no eyes; all the species possess either reduced, non-functional eyes or no eyes at all. Vision is replaced by vastly enlarged chemosensory organs, super-sensitive vibration detectors, and biological echolocation.

Without the presence of the sun, the creatures of the abyss cannot exist on primary producers. Thus, they live on organic material that washes down from the world above: "detrital snow", bacterial mats fueled by chemical seepage, and the bodies of dead surface dwellers. Detritivores, scavengers, and blind, slow-moving predators dominate the abyssal ecology. These creatures exhibit vastly slower metabolisms and exceptionally longer lifespans than surface-dwellers do, thanks to the stable thermal environment of the abyssal basins.

Behavioral Cycles (Vertical Migration and Geohazards)

The rhythms of behavioral cycles are not tied to the seasons of surface life, but to those of vertical migration, the weather and to the sheer randomness of geology. Due to the extreme depth of the abyss, an extremely stratified, "layer-cake" ecosystem exists within the canyon where different populations on different terraces might remain totally separate for centuries at a time. When conditions get dire on the surface, these separate layers are often forced together. Extremely hot surface droughts can cause surface-dwelling animals to migrate deep into the hot canyon to find stable water, and major floods on the surface can sweep light-sensitive animals from the abyssal basins into the sun-lit surface zones.

Rockslides and cliff collapses will cause an inevitable ecosystem "reset," and a new population of organisms will slowly, painstakingly colonize the newly exposed rock over a period of centuries.

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