Introduction
The hydration forms in shape of dome or tepee structure create at the bottom of the quarry in Dingwall contain an empty space, i.e. a rock chamber. The observations, drawings and measurements made with a laser rangefinder or geological compass show the diversity of rock chambers in many respects. The first important aspect is the internal dimensions in the form of length, width and height. Moreover, the detached thickness of the rock layer changes depending on the dimensions of the chamber and the presence at the bottom of the quarry. It is also crucial to determine the accessibility of the rock chamber to humans, because at first glance many chambers are penetrable by an adult human meeting the definition of a proper cave (Carl 1964). However, not all documented rock voids have this property. Moreover, the rock chambers have variable elongation orientations, a different shape of the interior or it is at different stages of development, which is directly influenced by the stage of evolution of the whole form.
Types of rock voids
In view of the fact that the rock chamber is an empty space, and that an integral part in their classification are the surrounding rock walls, the 5 types of rock chamber listed below have been created (fig. 1).
No entry cave.
Under the surface of the detached layer of gypsum-anhydrite rock, on the basis of observations and measurements in the field or during observations in the office, the presence of a rock chamber capable or probably able to accommodate an average human height can be found, however, the entrance is too small or has been obstructed by rock blocks, making the interior inaccessible or difficult to access. The minimum dimension for the height of the chamber is 30 cm in each direction. There are so-called caves with no entrance (fig. 2).
Chamber or cave impossible to measure.
In a situation where the rock chamber under the surface of the detached layer of gypsum-anhydrite rock cannot be examined on the basis of observations, field and chamber measurements. That does not make it possible to say whether there is a potential cave or rock shelter inside the form (fig. 3).
The chamber smaller than the cave.
It is a rock void, where, on the basis of field and chamber observations and measurements, the existence of a rock void under the surface of the detached layer of gypsum-anhydrite rock with an entrance enabling its partial or complete penetration however, of dimensions unable to accommodate the average height of an adult human (fig. 4).
Rock shelter.
It is a rock void where, on the basis of field and chamber observations and measurements, the existence of a rock void under the surface of the detached layer of gypsum-anhydrite rock was found. This rock void has dimensions able to accommodate the averaged height adult human and with an entrance allowing entry to the center with a minimum size of 30 cm measured in any direction (it is allowed for some size of the entrance to be shorter than 30 cm in a situation where a human can enter inside). The sunlight reaches most of the inner void (Urban 1996), and the structure of the cave consists of side walls and a ceiling part, but there is no back wall lying in front of the entrance, creating a tunnel-like shape. Moreover, the length of the cave is smaller than the dimensions of the entrance (fig. 5).
Cave.
It is a rock void where, on the basis of field and chamber observations and measurements, the existence of a rock void under the surface of the detached layer of gypsum-anhydrite rock was found. The rock void has a size that can accommodate the averaged height adult human and the entrance to the center with a minimum size of 30 cm measured in any direction (it is allowed for some size of the entrance to be shorter than 30 cm in a situation where a human can crawl inside). Sunlight does not reach every part of the inner void, and the structure of the cave consists of side walls, a ceiling part, and a back wall (Urban 1996). The length of the cave is longer, of similar dimensions or not much shorter than the entrance. There may be a situation where the entrance is greater than the length of the cave, and in some parts of the rock void it is dark (fig. 6).
