Geological Suitability Maps

GEOLOGICAL SURVEY DEPARTMENT MINISTRY OF AGRICULTURE What are the karstic phenomena NATURAL RESOURCES AND ENVIRONMENT (features) - sinkholes? REPUBLIC OF

Ground cracks at due to karstic processes With the term karst, which originates from the G in the substratum OLO IC karst region of the Dalmatian Alps in Croatia and RAL R A E ATU ES , N O L E U G R R Slovenia, we describe concisely the processes C U E T S L S

U S A U

C and features associated with chemical N

I D

R

U R

E G

N

A weathering - dissolution of rock by the action of R V V

F

I

R O

P E O

Y

N

R

M T

Y

Y water. Initially, this term was used to refer to S

E

I

N N I T M

C carbonate rocks (limestone, dolomite and 19 50 marble), afterwards it included sulphate rocks (gypsum and anhydrites). Eventually the term expanded to also include the halite (salt) sediments.

Karstic processes result in the creation of surface Sinkhole at Aradippou and underground cavities. Each cavity may have a different shape (circular or linear), size (small or large), depth (shallow or deep) and, of course, genesis type. The most common structures are KARSTIC sinkholes, usually of spherical shape, accompanied by ground subsidence (due to PHENOMENA - stress, earthquake, rainfall etc). Other forms of PROBLEMS IN cavities are dolines, crucibles etc. Generally, karstic features are considered to be GYPSUM ROCKS one of the most hazardous geological phenomena, as they often threaten the built OF CYPRUS Karstic cavity appearing during the construction environment and, furthermore they are not easily of - Dekeleia road detected. The threataffects mainly residences - settlements, roads and bridges, water works (dams and canals) and various other engineering works. Due to all of the above, particular attention is required from both geologists and engineers in order to deal with such phenomena prior to construction. This provision, done properly, will save money. Address: Mailing address: 1 Lefkonos street, , Lefkosia, CYPRUS Geological Survey Department Tel. : +357- 22409213, Fax : + 357- 22316873 1415, Lefkosia E-mail : [email protected] CYPRUS Webpage : www.moa.gov.cy/gsd

Prepared by Kleopas Hadjicharalambous, Geological Officer Director of Geological Survey Department: Dr P. Michaelides

Sinkhole in Maroni river bed Sinkhole at Maroni In cases where sinkholes appear in or near built up Causes of the development The main targets of this study were: The proposals of the study are summarised in the areas, the study proceeds to the development of of karstic features hazard area maps (suitability maps). These maps following: a) The geological mapping and the thorough study of show various zones in relevance to the degree of all the relative phenomena - problems from every The most common causes for the formation of karstic ground hazard due to the presence of sinkholes or any 1. To avoid constructing water works, e.g. dams, reservoirs aspect, features, e.g. sinkholes, are changes in the water other relative features. etc, on gypsum rocks, level and, generally, in the hydrological regime. Most b) The investigation on the causes and the sinkholes are often created after floods which mechanisms of their development / appearance, 2. To avoid any building development on chemically increase river flow. They can also appear after c) The proposal of solutions on those that already weathered gypsum, pumping of underground water and the drop of the influence unfavourably the structured environment, water level, assuming that the water, in such case, is and 3. To implement detailed geological / drilling exploration in to be chemically capable of dissolving the d) The creation of Geological Hazard Maps, in order to case of substratum composed by chemically- surrounding layer, e.g. gypsum. Moreover, seismic be used as a basis for future urban development and geotechnically vulnerable gypsum before the construction movements can also contribute in the appearance of planning. Karstic cavity appeared during the construction of any engineering work, if such work is mandatory, and sinkholes, in cases when roofs collapse due to of Agios Athanasios roundabout adoption of the most suitable foundation type, and seismic shaking. This study had obviously a multi - discipline approach and, consequently, included detailed geological Generally, karstic structures do not have a specific mapping of all the potential karstic areas, 4. In the case of structures already been built on gypsum: arrangement or shape / pattern and that is why they stratigraphic, tectonic and hydrogeologic evaluation are so difficult to be detected, especially at greater of the conditions, geophysical, geochemical and Avoid changing the water level, e.g. by pumping depths. This fact alone indicates the greatest severity hydrochemical investigation of the substratum and ground water, of the hazard in engineering works' foundations and, geotechnical - engineering assesment of the hazard Divert, where possible, the river flow away from eventually, in their stability and safety. Sinkhole at Nisou to the built environment. structures, Make impermeable, where possible, the river's bed The methods used were drilling, geophysical survey, in case its substratum consists of weathered Do sinkholes exist in Cyprus? sampling of underground water, laboratory and in situ gypsum, and tests, evaluation of air photos and satellite images, re - Fill, as soon as possible, any karstic cavity that There are sinkholes in Cyprus and their existence is appraisal of previous studies and observations and appears close to the foundation of any technical always related to the presence of gypsum. Nisou - finally, digital organisation, elaboration and work, especially residences, with suitable concrete, Pera Chorio, , Aradippou, Maroni, , presentation of the results with a geographic and make impermeable, preventively, its Pergamos and Mouttagiaka are the areas in Cyprus Filling with concrete an underground cavity information system (G.I.S.). substratum. where sinkholes (underground caverns) were discovered. In most cases, the sinkholes were located The findings of the study are recorded in seven (7) inside or close to the river bed and appeared after specialised volumes, altogether exceeding 600 pages The presentation of the results of the study took intense rainfall events causing an increased river flow. Studies/projects of the including a large number of maps, diagrams, tables place on December 2007 during a Pancyprian 1-day Geological Survey Department etc. This study resulted in the formulation of two (2) seminar in attended by more than 150 scientists Karstic features can also be observed in carbonate karst genesis models related to the gypsum rocks of (civil engineers, geologists, city planners, architects) from rocks. Characteristic big karstic structures in Cyprus: The Geological Survey Department was, government services, town and village councils, ETEK (the carbonate rocks have developed in the Pentadaktylos Sinkhole at Pergamos Sinkhole at Nisou diachronically, dealing with the appearance of karstic Technical Chamber) and various other scientific mountains. These structures are often accompanied features in the gypsum rocks of Cyprus, and a) The model of Nisou - Pera Chorio and Tochni, organisations. by big springs (kefalaria), which (for now) are all dried especially, their effects on the built environment. which is considered to be in a “mature” (old) phase up. because of its numerous, large - sized karstic Originally, the G.S.D.'s studies were concentrated in structures, and local minor cases where the appearance of karstic b) The model of Aradippou, which is considered to be Methodology in studying the phenomenon features caused danger to the built environment (e.g. in an “immature” (young) phase because of its limited, residences, roads, bridges, canals, farms) in the small - sized karstic structures. The study of karstic features and their effect on the areas of Nisou - Pera Chorio, Tochni, Aradippou, built environment require an interdisciplinary Mouttagiaka, Kalavasos, Maroni etc. The products of the study are various maps, such as approach, in which the expert knowledge of an geological, geotechnical, hydrogeological etc. The engineering geologist, geotechnical engineer, most important of them are the geological suitability Eventually, in 2004 - 2007, the Department proceeded hydrogeologist, geophysicist and geochemist is maps, concerning the areas of Nisou - Pera Chorio, - in collaboration with the Institute of Geological and essential. This study includes detailed geological Tochni, Mouttagiaka, Aradippou, Maroni and Agios Mining Research of Greece and its Collaborators - to a mapping, drill holes, geophysical research, Athanasios () - displaying the high risk areas detailed, documented study titled “Karstic hydrogeological research, geotechnical investigation in relevance to the presence of karstic structures and phenomena - problems in gypsum rocks of Cyprus” relevant to the built environment, water and soil consequently the management of town planning. which covered the whole island. sampling for chemical analysis. Sinkhole at Tochni Photograph from the Pancyprian 1-day seminar (1.12.2007)