*2.2.3.1 Mineral transformations*

These transformations constitute an important environmental problem for deformations resulting from volume expansion and especially for settlement areas (such as structural damage) and agricultural-water areas. In addition to gypsum (CaSO42H2O), which is one of the minerals of the evaporite group, anhydride (CaSO4) and other minerals of the evaporite group are easily soluble when they contact with water (**Figure 5a–c**).

In the event of the loss of water in the environment, these minerals may be recrystallized, new minerals may be formed by the displacement of ions, or minerals may transform into each other. For example, as gypsum (CaSO42H2O) absorbs heat (as temperature increases) depending on climate conditions, it loses water and may transform into gesso (CaSO4½H2O) and anhydride (CaSO4) units, respectively [3]. On the other hand, the melting temperature of gypsum is very high (about >100°C or about 700–1500°C), the dissolution temperature of gypsum

*Natural Hazards - Risk, Exposure, Response, and Resilience*

the building (**Figures 2–5b, c**).

**Figure 3.**

*Sivas.*

sion of the environmental problem.

*2.2.3 Health and living environment of living beings*

doline, erosion, corrosion, rockfall, etc.) arise and are observed in the structures of

*Gypsum-based karst deformations in Sivas (Turkey) (photos: Sevda Özel 2013, 2015). (a) The collapse area, sinkholes, and the gypsum clastic soils in the east and northeast of Sivas. (b) The rockfalls in the northeast of* 

Vegetation losses also occur with soil salinization occurring with leachate waters containing the high amounts of dissolved ions mixing into the water from gypsum as a result of the contact of gypsum with water in cover units on the edges or on gypsum. In this case, erosion may occur in these regions over time (**Figures 4a** and **5b, c**). Therefore, all living beings including humans, and their living environments are damaged by these losses. Hence, low water-soil quality decreases and destroys the nutritional sources of living beings; soil-water pollution, as well as inadequate nutrition conditions, affect the health of living beings, and plant species may become extinct or decreased due to erosion (**Figure 4a, b**). Similarly, living beings may have to migrate to living environments where healthier and better opportunities exist. The health and living environments of living beings are impaired with these exposures in the dimen-

While discussing the dimensions of environmental impacts in terms of the settlement by reviewing the detailed characteristics of the environment, hydrogeological and hydrogeophysical investigations are important in this regard. In particular, it is necessary to perform well-planned field studies that determine shallow and deep geological/geophysical, hydrogeological and environmental impact characteristics of the gypsum karst region. Whether the Environmental Impact Assessment (EIA)/Strategic Environmental Impact Assessment (SEIA)

*(a) The erosions in the east of Hafik-Sivas (Turkey) (photo: Sevda Özel, 2013). (b) The gypsum clastic agricultural soils in the east and northeast of Sivas city (Turkey) (approximately 1–2 km away from the city)* 

**116**

**Figure 4.**

*(photo: Sevda Özel, 2013).*

#### **Figure 5.**

*(a) Gypsum samples collected from the northeast and south-southeast of Sivas (Turkey) (photo: Sevda Özel, 2005, 2007, and 2010). (b) Surfaced gypsum in the northeast of Sivas (Turkey) (photos: Sevda Özel, 2015) (c) Gypsum karstic deformation structures (cave, fracture, crack, collapse) from Hafik Formation in Sivas (Turkey) (photo: Sevda Özel, 2017).*

is very low (about 0–50°C) [33–35]. For example, the solubility of gypsum in pure water at 20°C is 2.531 g/L [34, 36]. Gypsum is about 10–30 times more soluble than limestone, and it commonly has a lower mechanical strength [3, 15, 23, 33, 34]. However, between 0 and 30°C, the range encompassing most natural waters, the solubility of gypsum increases by 20%, reaching a maximum (about 2.66 g/L) at 43°C [34]. Therefore, sudden collapses in gypsum areas are a great danger for both life and property [3]. Therefore, the quality of water in the basins where the rock types formed by these minerals dominate is easily impaired, and surface and underground waters in which evaporite group minerals are dissolved are naturally polluted [4, 6, 38]. These polluted waters also pollute fertile soils if they leak into the soil.

Evaporite units tend to expand and swell depending on their origin, and these unites may also involve areas where underground waters are collected, and the sources where underground waters rise to the surface [3]. Upon examining **Figure 1** it is observed that, a shallow or deeper ground cover may develop or soil development may not occur at all in these areas. If the karstic area is surfaced, these areas are open to external factors (e.g. precipitation, wind, temperature) and processes (e.g. dissolution, erosion, deterioration). In this case, cracks in various directions, dense joint systems, melting areas, and various karstic structures begin to occur in gypsum areas. Moreover, larger fractures or new faults may occur as a result of seismic activity and collapse events. Furthermore, rock (block) fall events may also occur in rocks where slopes are perpendicular [12]. According to all these geological characteristics, significant ground problems are encountered in the existing buildings in the area or during and after new construction with the use or selection of gypsum areas as settlement areas (**Figure 1a,b**). These areas should be included in the class of areas with risky areas, especially if such areas continue to be selected as new settlement areas.

#### *2.2.3.2 Pollution*

There is always a risk of pollution in soil and underground/surface waters in gypsum areas. This pollution problem takes place as a result of salinization. Gypsum units may lead to salinization by ion decomposition resulting from the contact with water. Waters with the intense ion content formed during salinization threaten underground waters, surface waters, soil quality, and the life of plants, animals, and humans in the places of their passage, as leachate waters. In other words, leachates are the waters containing inorganic pollutants, and they also interact with other materials. This also reduces the existing underground/ surface water quality and decreases the soil fertility, plant diversity, and the

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*Identification and Assessment of Hazard of Development in Gypsum Karst Regions: Examples…*

acquisition of fertile product [5, 6, 24, 27, 29]. The pollutants mixed in the soil also affect living beings in the soil, plants that grow/are grown in the soil, or

Since gypsum units geologically have swelling-expansion characteristics due to their mineralogical structure, they cause swelling in the ground. Thus, ground and structure deformations caused by the swelling of gypsum grounds, and material

(**Figures 2a,b** and **5b**). In these situations that endanger the safety of buildings, the life of human and living beings will also be under risk due to the safety problem (**Figure 2**). On the other hand, gypsum units may also be covered with alluvial units in some places. In this case, similar ground swelling problems may occur if units with swelling properties like clay are found in the alluvial filling material. Therefore, it is necessary to control leachate and underground waters in the

Corrosion may occur on the grounds of gypsum areas and in the immediate vicinity of them, and in structures (**Figure 5b**). In particular, there is a corrosive effect on installation, building foundation, and substructures. It leads to rapid deterioration, and rusting and corrosion of materials in buildings and substructure pipe systems. Underground corrosion results from chloride (Cl) dissolved from the evaporite units in the caves in the soil, sulfate salts (SO4), and dissolved gaseous oxygen (O). As a result of the fact that these dissolved ions cause stress difference in metal and electrolyte, they are oxidized to the metal ion in the anode or realize the corrosion (on the micro- or macroscale) event by passing into the solution as a metal ion [39]. Therefore, corrosion is one of the environmental problems arising from the gypsum unit since it causes damage to structures,

They pose a threat to people and structures or to agriculture and water areas in and near settlement areas in places where karst-type structures such as fractures/cracks, dissolution caves, and dissolution channels develop [28, 40] (**Figures 2–5b,c**). In the regions with intense collapses, hazardous areas that cause a safety problem for human and other living things emerge. Furthermore, agricultural areas, water resources, road routes, as well as settlement areas are also damaged. Therefore, a safety problem exists not only in settlement areas and in the immediate vicinity of them but also outside of them, and it affects the lives of all living beings. Furthermore, these problems also pose risks to

It is also important to monitor seismic activity in and around these areas. In a region which is active in terms of seismicity, fractures, faults, and subsidence dissolution caves/areas in gypsum units, and changes in underground water levels should be monitored because new deformations may develop over time and new

dissolution caves/areas may also occur (**Figures 1a** and **5b, c**).

damages occur on superstructure grounds and in substructure systems

*DOI: http://dx.doi.org/10.5772/intechopen.83684*

living beings fed with these plants.

construction areas in both cases.

building systems, and soil.

*2.2.3.5 Karst structures*

national economies.

*2.2.3.6 Seismic activity*

*2.2.3.4 Corrosion*

*2.2.3.3 Ground damage*

acquisition of fertile product [5, 6, 24, 27, 29]. The pollutants mixed in the soil also affect living beings in the soil, plants that grow/are grown in the soil, or living beings fed with these plants.
