Cave interior - physical notes and invented extension
Working notes for the interior of the cave. The entrance is Nenápadná diera; the interior is borrowed from Alabastrová jaskyňa. The first half is sourced and reasoned. The second half is invention and is marked as such.
The sourced interior #
Alabastrová is at 1,390 m on the south-east slope of Bujačí vrch, in the Belianske Tatry. Registered, closed to the public, protected since 1961 for its dripstone. Discovered 1830. Sealed since 1981. The register gives a name and a range, not a description.
Its classification is fluvio-krasová-rútivá, so stálym priesakom zrážkových vôd - fluvio-karst collapse, with permanent seepage of precipitation water. In it are sinter coatings and secondary gypsum. Length is given as 400 m by Wikipedia and 300 m by Encyclopaedia Beliana; treat the extent as approximate. The main passage holds a karst pool and a waterfall.
Acoustics, corrected #
An earlier note called the cave loud. That was too broad. The noise belongs to one stretch, the fall.
The fall is not a tributary. It is the pool’s spillway. The pool is upstream of it and the passage below the lip is the drain. Water goes over the lip only when inflow outruns what the pool can hold and pass.
That makes the fall a gauge, not a fixture. Running fall means the pool is at or above the lip and the water table is high. A dry fall means the pool sits below the lip and the cave is quiet. So the noise is a wet-weather state, and the sound tells you which.
The pool itself is fed from below, by the water table rising through the floor. There is no inflow jet at the surface, so it sits glassy. The only disturbance is a faint boil or ring directly over the feeder, spreading from a point rather than an edge.
The loud and the quiet are different water in the same passage.
The pool surface #
In still air a cave pool is two hard surfaces.
It goes to a mirror. No wind means no capillary ripple, so it reflects the ceiling inverted, brighter than the rock it reflects. That is what makes still water read as a hole rather than a floor. The reflection shows depth where there is none and a reflected passage mouth looks like a passage mouth. People step in for that reason.
It is also the most reflective thing in the cave acoustically, unlike damp sinter which absorbs. A flat pool under a low ceiling gives a flutter echo. A voice carries further across water than along rock. The fall masks, the pool amplifies.
Chemically the surface is the active face: it is where carbon dioxide leaves the water, so it is where calcite drops out. A mineral film can skin over, sometimes as floating rafts. The margins build their own rimstone lip. Touching it breaks a crust that took weeks.
A broken surface takes minutes to settle, and each ring flashes light across the ceiling, visible from well down the passage.
Temperature and humidity #
The water regulates the cave more than the rock does. Rock is a poor short-term regulator - high mass, low conductivity. Water moves heat far better, and flowing water holds the passage near its own temperature. A stream cave therefore has a narrower, steadier band than a dry one at the same altitude.
The cave will not freeze in the body of it. Flowing water does not freeze and sinter does not deposit on a frozen surface.
The benchmark is Belianska jaskyňa in the same limestone, which holds 5.0-6.3 degrees C year round at 90-97 per cent relative humidity. Expect Alabastrová at or somewhat above that. It is reported to run warmer than the other caves of the massif, which are mostly static or ice-bearing - Ľadová pivnica next door is named for ice and has no decoration at all. Read “warmer” as relative to a cold set: seven or eight degrees, not comfort.
The entrance zone is not the cave. A downhill entrance drains cold air in winter and holds it, which is why the neighbouring feature is an ice cellar. Alabastrová’s threshold will be colder than its interior and can carry ice. A frozen threshold looks unused, which is useful.
The real risk is wet cold, not cold. At 5-8 degrees and near saturation, wet clothing loses almost all insulation. Plus five and soaked is worse than minus five and dry. The interior is survivable; getting to it strips the heat out of you.
A water-table pool is not a fixed level. It rises with melt and after rain. In a hard thaw it can fill the low passage. Late summer is the safe window; spring melt is the wrong time to be in there.
The invented extension #
A passage leaves the pool cavern above the spillway lip - above it, not at pool level, so the chamber is immune to the pool rising. It climbs away from the table into the vadose zone, which is dry by definition.
It reaches a small chamber, roughly four by three metres. Floor of clay and rubble, sloping gently back out toward the entry so spill runs off. Sleeping bench at the high end on a rubble plinth.
The warmth is modest and comes from the pond air drifting up, not from the rock. One to three degrees over the pond cavern. Six to nine rather than five to seven. The gain is dryness and draught, not temperature.
The flue #
The flue rises at a shallow angle into an adjacent void, probably a deeper inaccessible part of the cave. It does not reach the surface.
The geometry is the whole point. Water only enters a passage it can run downhill into, so a flue rising away from the chamber has no downhill path back to it. Anything arriving in the far void falls down that void’s own walls and goes to the lake. The inner opening stays dry by geometry, not by a seal.
Three requirements:
- Throat at the highest point of the roof, as a slot. Not a wall hole with a sill - a sill is a lip water can run back over. The roof rises to the throat so the chamber ends in a small bell. The bell gathers warm air and smoke and spills them only once full, and the trapped pocket resists cold cascade.
- Shallow angle, narrow bore. Both work against downdraught. The far void must vent somewhere and in winter cold air will want to sink the path. Shallow and narrow plus the bell keeps the draught weak and one-way enough for a small fire.
- Rodable from below. The void is inaccessible, so a blockage cannot be cleared from the far side. The throat must be reachable from the chamber roof with a stick, which caps chamber height at about a standing reach plus the rod.
Smoke works its way out through the jointing of the void and seeps from the hillside above as faint haze on a cold still morning, with a band of moss or lichen that stays green when everything else is frosted. On a cold morning a wisp above the slope is what gets a hidden camp found.
The flue and the near wall of the void soot up within days. That blackening is a permanent record and survives after the fire, the bedding and the people are gone.
Fire and the chamber #
Fire goes at the throat, low, directly under the flue. A small flame at the throat to establish draught, because a small closed space smokes until it does.
Efficiency measures, in order of value:
- Bell and hood - concentrates hot gas at the throat, cuts smoke in the room.
- Controlled low inlet opposite, with a stone to part-block it. Without an inlet you get a smoulder or a race. This is the difference between tar and heat.
- Low baffle wall in front of the fire so gases travel over it before the throat. Longer path, better burn.
- Flat hearth slabs and an angled back reflector.
- Modest thermal mass behind the hearth, enough to re-radiate after the fire dies and not so much it never warms.
- Raised bench with a stone kerb in front - warm air is at bench height, the draught is along the floor.
- Part-screen at the entrance of stones and brush, which must still pass combustion air.
Fuel #
A 35 cm spruce carries 0.6-0.9 cubic metres of stem, 270-400 kg air-dry, which is 30-50 nights at 8-10 kg. Two well-scattered trees is a season’s fuel and worth the axe work.
Fell across the slope, not downhill - a stem lying downslope runs away and rolls. Choose trees under standing canopy so the gap is broken from above, and put the two at least a hundred metres apart so no sightline shows both. Cut the stump low and chop it out; a dressed stump fills with needles and reads old. Take the top and branches, which are the best small-fire fuel, and scatter the brash. Sweep the sawdust.
Bow saw for felling and sectioning, axe for splitting only. Split on site into forearm lengths - it halves the carry and it is the only thing that makes green wood burn.
Drying is the bottleneck and the cave is the worst place for it. Fresh spruce is over half water and yields about half its heat while throwing tar. Split small it is usable in six to eight weeks in dry moving air. Wood dries against the flue on the rack, over the fire, and the first weeks are poor regardless.
Furnishings #
Function first. Limestone is soft, splits flat along bedding, is good in compression - so it carries. Spruce is weak, rots fast - so it spans and wears, but does not touch the floor.
The governing rule: no wood in permanent floor contact. Wet floor plus rot plus calcification eats a post foot in a season. Every timber stands on a slab. Every joint is wedged, not fitted, because green wood shrinks and a tight joint is a loose one in a fortnight.
Order of work: hearth, bench, rack, table, niches, pegs, screen. Incremental, not a fit-out.
Slabs split along bedding with wedges, edges dressed with the axe poll. Wet the stone before dressing or the dust settles over the bedding. Work stone outside and haul slabs in.
Anything under an active drip is encrusted within weeks - site clear of the drip line and shield what cannot move. Anything within a metre of the hearth chars - stand it on stone. Boughs go flat and must be renewed every two to three weeks, a standing obligation.
Latrine #
An alcove off the approach passage, not in the chamber. The approach is the draught path, so a latrine there is upstream and its smell is drawn in. Four fixes, none of which is moving it back:
- Dog-leg the alcove - air exchange in a pocket you must turn into is slow by geometry.
- Step it down - puts the seat in the sluggish cold layer.
- Slab lid - the most effective control regardless of siting.
- Ash and earth after use.
Lidded bucket rather than a pit, emptied to a rubble slope below on a long interval. Keep it on the far side of the passage from the water line so nothing runs toward the pond.
Consumables and resupply #
Modern items change the shape of the stay more than any cave modification, and they cut both ways.
Light is the big one - a lamp or candles let the fire be banked low and burned less. But every litre of paraffin burned puts about a litre of water vapour into the air, which comes back as condensation. Paraffin also smells, and the smell gets into clothing.
Keep the lamp in the niche, never under the rack or the boughs, and trim it - a bad flame soots the ceiling as surely as the fire.
The rest of the list is unglamorous: bucket, trowel, saw, axe and wedge, grindstone, cordage, tarp, water containers, pot and kettle, tin plates, first aid, repair kit, sewing kit, spare laces, desiccant, thermometer and hygrometer.
All of it is consumable, so each running-out is a trip out. The modern items do not reduce exposure, they convert it into a calendar. The stay acquires a resupply rhythm, and the rhythm is what a watcher would eventually notice. Vary the interval, buy in Poprad rather than the village, buy small for cash.
Salamanders #
Salamandra salamandra is at or above the top of its band at 1,390 m, and the forest there is spruce, the wrong litter. It wants damp mixed and beech wood with rotting hardwood and a brook for the larvae - below roughly 1,000-1,100 m in the Tatras.
Reliable ground is the beech belt, three to four kilometres down and 500 to 850 m below. A half-day round trip.
Their fuelwood comes from 1,300-1,400 m, above the band, so logs are mostly clean. A salamander in the fire is likelier after a foray lower down, in wood gathered in the beech belt.
They are surface-active in spring and autumn in wet weather, mostly at night. Autumn is the better and wetter trip. Summer they are deep in rotting wood and under stones.
Tatras populations are larviparous - larvae are deposited in the brook. Terrestrial birth belongs to the Iberian subspecies and, fully, to the Alpine salamander over the ridge, not to the local animals.
The folklore is sound: the fire lizard, Feuersalamander, Pliny before that. The log is the mechanism. They exude a milky toxin, so are handled little, which adds to the impression of something unbothered by flame. Protected in Slovakia.
Settled - do not reopen #
- Entrance Nenápadná diera, interior Alabastrová, valley Dolina siedmich prameňov. No booth.
- The fall is the spillway, downstream of the pool. The pool is spring-fed and still.
- Chamber above the spillway lip, not at pool level.
- Flue is blind, into a void, shallow, narrow, with a roof bell. Not to daylight.
- Water is carried up from the pond. No drain or sump in the chamber.
- Latrine in the approach alcove, dog-legged and stepped down.
- Discovery is accepted. Function outranks concealment inside the cave.
Prompts for a fresh agent #
- What does the smoke do in the first ten minutes after lighting, and what does that tell the characters about the flue?
- How often does the throat need scraping before it visibly narrows?
- What does a hard autumn thaw do to the low passage, and what is the retreat?
- How much wood is a night, measured rather than guessed?
- Which of the consumables runs out first, and what does the trip for it look like?