Stalactites. Types of stalactites

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Cave stalactites have always been of interest to people. Among the nalectic stalactite formations there are gravitational (thin-tubular, cone-shaped, lamellar, curtain-shaped, etc.) and anomalous (mainly helictites).

Thin-tubular stalactites

Especially interesting are thin-tube stalactites, which sometimes form entire calcite thickets. Their formation is associated with the release of calcium carbonate or halite from infiltration waters. Having seeped into the cave and having got into new thermodynamic conditions, infiltration waters lose part of carbon dioxide.

This leads to the release of colloidal calcium carbonate from the saturated solution, which is deposited along the perimeter of the drop falling from the ceiling in the form of a thin roll. Gradually building up, the rolls turn into a cylinder, forming thin-tubular, often transparent stalactites.

The inner diameter of tubular stalactites is 3-4 mm, the wall thickness usually does not exceed 1-2 mm. In some cases they reach 2-3 and even 4.5 meters in length.

Cone-shaped stalactites

Among the stalactites , cone-shaped stalactites are the most common ones Their growth is determined by water flowing down a thin cavity located inside the stalactite, as well as by the flow of calcite material on the surface of the overflow. Often the inner cavity is located eccentrically. Clear water drips from the opening of these tubes every 2-3 minutes.

The sizes of cone-shaped stalactites, located mainly along the cracks and well indicating them, are determined by the conditions of calcium carbonate intake and the size of the underground cavity.

Usually stalactites do not exceed 0.1-0.5 m in length and 0.05 m in diameter. Sometimes they can reach 2-3, even 10 m in length (Novoafon cave) and 0.5 m in diameter. Interesting are spherical (bulbous) stalactites formed as a result of blockage of the tube opening.

Aberrational thickenings and patterned growths appear on the surface of the stalactite. Spherical stalactites are often hollow due to secondary dissolution of calcium by the water entering the cave.

Anemolites are curved stalactites

In some caves, where there is significant air movement, there are curved stalactites - anemolites, the axis of which is deviated from the vertical. The formation of anemolites is determined by the evaporation of hanging water droplets on the leeward side of the stalactite, which causes it to bend in the direction of air flow. The angle of bending in some stalactites can reach 45°.

If the direction of air movement periodically changes, zigzag anemolites are formed. Similar origin with stalactites are curtains and draperies hanging from the ceiling of caves.

They are associated with infiltration water seeping along a long fissure. Some curtains, consisting of pure crystalline calcite, are completely transparent. In their lower parts there are often stalactites with thin tubes with water droplets hanging from their ends.

Calcite deposits may look like petrified waterfalls. One of such waterfalls was noted in the grotto of the Novoafon (Anakopi) cave in Tbilisi. It is about 20 m high and 15 m wide.

Helictites

Helictites are complexly constructed eccentric stalactites that are part of the subgroup of anomalous stalactite formations. They occur in various parts of karst caves (on the ceiling, walls, curtains, stalactites) and have the most diverse, often fantastic shape: in the form of a curved needle, complex spiral, twisted ellipse, circle, triangle, etc.

Needle-shaped helictites reach 30 mm in length and 2- 3 mm in diameter. They represent a single crystal, which as a result of uneven growth changes orientation in space. There are also polycrystals, grown one into another.

In the section of needle-shaped helictites, growing mainly on the walls and ceiling of caves, the central cavity is not traceable. They are colorless or transparent and their end is pointed. Spiral-shaped helictites develop mainly on stalactites, especially thin-tubular ones.

They are composed of many crystals. A thin capillary is found inside these helictites, through which the solution reaches the outer edge of the aggregate. Water droplets formed at the ends of the helictites, unlike tubular and conical stalactites, do not come off for a long time (many hours).

This determines extremely slow growth of helictites. Most of them belong to the type of complex formations with intricate shapes. The complex mechanism of helictites is currently still insufficiently studied. Many researchers (N.I. Krieger, B. Jezet, G. Trimmel) the formation of helictites associated with the blockage of the growth channel of fine-tubular and other stalactites.

Water entering inside the stalactite penetrates into cracks between crystals and comes to the surface. This is how helictites begin to grow, due to the predominance of capillary and crystallization forces over gravity.

Capillarity is apparently the main factor in the formation of complex and spiral-shaped helictites, the direction of growth of which initially depends largely on the direction of intercrystalline cracks. F. Chera and L. Mucha (1961) proved by experimental physicochemical studies the possibility of calcite precipitation from cave air, which causes the formation of helictites.

Air with relative humidity of 90-95%, oversaturated with tiny water droplets with calcium bicarbonate, turns out to be an aerosol. Water droplets falling on the ledges of walls and calcite formations quickly evaporate and calcium carbonate precipitates.

The highest rate of calcite crystal growth is along the main axis, causing the formation of needle-shaped helictites. Consequently, under conditions where the dispersion medium is a substance in the gaseous state, helictites can grow due to diffusion of dissolved matter from the surrounding aerosol.

Helictites created in this way ("aerosol effect") have been called "cave frost". Along with the colmatage of the feeding channel of individual thin-tubular stalactites and the "aerosol effect", according to some researchers, the formation of helictites is also influenced by the hydrostatic pressure of karst waters (L. Yakuch), the peculiarities of air circulation (A. Vikhman) and microorganisms.

These positions, however, are insufficiently argued and, as studies of recent years have shown, are largely debatable.

Thus, morphological and crystallographic features of eccentric natellite forms can be explained either by capillarity or aerosol influence, as well as by a combination of these two factors.

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