## 2 Geoenvironmental Setting
The fact that within the area, individual aquifers have been connected has led to the assumption that for the purpose of considering the problems of the risk of water inflow to the underground workings, and also the problem of surface protection, there is in practice one aquifer that covers both the salt dome and the rocks surrounding it. Because of this assumption, it was thought that it is only mining activity that has caused the creation of numerous underground channels, through which water from mainly Jurassic formations began to flow to the cap, and then cleared the caverns and fissures within it. Based on the observation of the distribution of sinkholes, it can be stated that there are certain directions, or more precisely, certain zones of tectonic disturbances. The most elevated part of the deposit is in the central-eastern part, in which there are clay salts. These salts are the most resistant to leaching by flowing waters. From this area, the dome surface descends in all directions, but definitely more towards the west, then towards the south and east. This is the result of the lithology of the rocks that make up  
Figure 2: Geological setting and tectonics of Inowroclaw salt dome (cross section after [16] modified). the interior of the dome, where the northern part is made up of older, pure salts with a minimum amount of anhydrite sand. They run south on the west side and pass to the east side in the middle of the southern part of the dome. Therefore, the runoff of underground waters on the diaphragm also runs from the north-west to the south. The flow of water thus refers to the topography of the roof part of the dome. The almost horizontal surface of the salt table in the central part turns with a gentle slope into the inclined side surface of the dome in the eastern part, initially under the gypsum cap, and then reaches greater depths under the Jurassic rocks [13; 14; 15]. The southern and western parts are more morphologically diversified, especially in the area analyzed here. In the southern part, the roof part of the salt structure arcs into the sloping side surface of the dome. It does so similarly in the northern part, while in the western part, it turns into a vertically collapsing side surface. Thus, it can be concluded that the topography of the dome's roof, its lithology, and hydrogeological conditions are interrelated and are determinants of both the terrain morphology and of the deformations in the area. Mining, Non-Mining and Post-Mining Displacements--A Brief History of the Development and Monitoring of Ground Deformation in Inowroclaw  
In the more than 100-year history of exploitation of the salt deposit in Inowroclaw, mining operations were carried out in different periods, using various methods of salt extraction [18]. The date of the beginning of the history of modern mining activity in the area of Inowroclaw is 1871, when the Ost borehole revealed salt at a depth of 129.64 m. Salt was found in most of the boreholes drilled in subsequent years. As a result, two competing enterprises developed, operating in separate mining plants (Kronprinz mining field, Inowroclaw Salt Mine, Kronprinz, years 1873-1888). This exploitation consisted of obtaining salt from brine pumped from boreholes [14; 18]. This pioneering period in the history of salt mining in Inowroclaw was short-lived, and its end was related to the existence of hydraulic connections between the wells exploiting brine and a significant reduction in the level of brine in the boreholes [13; 15]. This led to the state-owned company deciding to establish an underground mine. As a result, the I shaft and underground excavations were sunk, and the encountered brine sources were captured. At the same time, underground mining works were carried out by a private mining company. The exploitation carried out at that time covered the roof part of the deposit and was aimed at obtaining brines from natural sources that existed in the crevices encountered.