## 6 Discussion
The legend presents the signatures used on the map and their numerical designations. Their meaning is as follows: 1—boundary of the area under study; 2—workings of the shallow mines from the beginning of the twentieth century; 3—sinkholes that existed before 1861, according to [18]; 4—sinkholes that occurred after 1861, according to [18]; 5—boundary of the salt dome at the depth of 470 m; 6—historic, currently non-existent railway lines; 7—abandoned mine shafts; 8—boreholes. the number of the changes in which the values are above the error value increased during the longer time interval and the changes in positive values became more frequent. The same conclusion can be drawn from an examination of the height change maps (Figure 6). As shown in the figure, only minor zones in the area under study showed negative height changes (subsidence) at a significant value. Zones of the height changes which were determined for the 1978-2018 time interval are clearly noticeable: the southern part of the area represents uplifts, whereas in the northern area, a large variability was recorded. Both positive (uplift) and negative (subsidence) height changes can also be distinguished. The zone of uplifts in the northern part of the area under study is placed in its central part, while on the western and eastern sides, subsidence has been found. While the areal distribution of the height changes seems complicated, the profile line distributions are more understandable, especially if the distributions of these changes are related to the profile of the salt roof surface. Four profile lines that run through characteristic zones in the area under study were selected for analysis. Three of them (W1, W2, W4 profiles) pass latitudinally through the area and the other one of them passes it nearly longitudinally. The W4 could be considered an essential profile line because of the fact that it runs just above the workings of shallow mining and their catastrophic flooding and collapse in 1907. The profile lines were also as follows in light of the means of the characteristics of the elevation of the salt layer of the dome, as well as the characteristics of the terrain surface in the years 1978, 1998, 2018:  
* The W1 profile line runs over flooded workings in the area of the Solno 1 shaft, and this part of the area in recent decades was not significantly affected by mining, and all mining works were stopped there in the 1960s [18]. Furthermore, as in this part of the area, no sinkhole has been documented as having appeared, this zone can be defined as being non-hazardous from the point of view of this particular risk. As can be seen in the W1 profile, in the first period (1978-1998) the changes in height were relatively insignificant (Figure 9). Only in the central part of the profile were there uplifts on the edges and subsidence, which in the eastern part of the profile showed significant values, i.e., values twice as large as the error in determining the height change. The topographic profile reflects the morphology of the top of the salt rocks of  
Figure 8: Histogram of height changes of points (in meters) for the assumed time intervals and the location of reference points (from 1978) on the right. the diapir, but a certain horizontal shift in the characteristics of the profiles is visible. The ten-meter relative heights of the roof surface of salt correspond to the one-meter differences in the terrain profile. As shown, the height changes which occurred in the first short period (1978-1998) mostly amounted to negative values, although at a value close to zero, which made them not significant. In the next short period, the characteristics of the changes are more clearly defined and uplifts dominate, especially in the eastern part of the profile. Finally, in the longer time interval (1978-2018), only positive changes can be found, usually producing results well above the error value.