Karst of Romania

Romania is situated in the Eastern part of Europe, with an area of 237,500 km² (91,671 sq. miles) and consists of four regions: Walachia, Moldavia, Transylvania, and Dobruja. The topography of Romania is dominated by the Carpathian Mountains, which are divided into the Eastern Carpathians, the Southern Carpathians, and the Western Carpathians.

The Eastern Carpathians (Carpatii Orientali) extend from the Ukrainian border to the Prahova River, with maximum elevation in Rodna Mountains (Pietrosul Peak - 7,556 feet or 2,303 meters). The central core of these mountains is made of crystalline rocks and in part of limestones and conglomerates, through which Bicaz River has cut a narrow gorge (chei). On the eastern site is bounded by a flysch zone. For some 250 miles (400 km) on the western fringe are situated the volcanic ranges Oaș and Harghita (Muntii Oasului and Muntii Harghitei), with a concentration of volcanic necks and cones, some with craters still preserved. In one of these craters, the Saint Ana Lake (Lacul Sfinta Ana) is located (modified from Encyclopedia Britannica webpage, with additions).

The Southern Carpathians (Carpatii Meridionali) or Transylvanian Alps, lie between the Prahova River to the east, the Timiș and Cerna Rivers to the west, and Danube River to the South. They are composed mainly of crystalline and volcanic rocks. The highest points in Romania are reached in the peaks of Mounts Moldoveanu (8,346 feet or 2,544 meters) and Negoiu (8,317 feet or 2,535 meters), both in the Făgăraș Mountains, which, together with the Bucegi, Parâng, and Retezat-Godeanu massifs, form the major subdivision of the region (modified from Encyclopedia Britannica webpage, with additions).

The Western Carpathians (Muntii Banatului and Muntii Apuseni) extend for about 220 miles (350 km) between the Danube and Someș Rivers. They form a cluster of massifs around a north-south axis. To the north lie the Apuseni Mountains, centered on the Bihor Massif, from which emerge fingerlike protrusions of lower relief. On the east, the Bihor Mountains merge into the limestone plateau of Padis/Cetățile Ponorului. To the west lie the parallel mountain ranges of Zărand, Codru-Moma, and Pădurea Craiului; to the south, along the Mureș River, the Metaliferi and Trascău mountains (modified from Encyclopedia Britannica webpage, with additions).

The great arch of the Carpathians is accompanied by an outer fringe of rolling terrain known as the Subcarpathians and extending from the Moldova River in the north to the Motru River in the southwest. It is 2 to 19 miles (3 to 31 km) wide and reaches elevations ranging between 1,300 and 3,300 feet (400 and 1,000 meters) (modified from Encyclopedia Britannica webpage, with additions).

Inside the Carpathians arch, the Transylvanian Basin is placed and has an average elevation of 1,150 feet (350 meters). In the east, between the outer fringe of the Subcarpathians and the Prut River, lies the Moldavian Plateau, with an average elevation of 1,600 to 2,000 feet (500 to 600 meters). The Dobruja (Dobrogea) is an ancient, eroded rock mass in the southeast, has an average elevation of 820 feet (250 meters) and reaches a maximum elevation of 1,532 feet (467 meters) in the Pricopan Hills.

Plains cover about one-third of Romania. In the southern part of Romania is the Walachian/Romanian Plain (Cimpia Romana), which can be divided into the Romanian Plain to the east of the Olt River and the Oltenian Plateau to the west. The whole region is covered by deposits of loess, on which rich black chernozem soils have developed, providing a strong base for agriculture. The Tisa (Western/Pannonian) plain developed along the Timis, Mures, Crisul Alb, Crisul Negru, and Crisul Repede Rivers, with its chernozem soil, is important economically (modified from Encyclopedia Britannica webpage, with additions).

On the northern edge of the Dobruja (Dobrogea) region, adjoining the Moldavian Plateau, the great swampy triangle of the Danube delta is a unique physiographic region covering some 2,000 square miles (5,180 square km), of which the majority is in Romania. The delta occupies the site of an ancient bay, which in prehistoric times became wholly or partially isolated from the sea by the Letea sandbanks (modified from Encyclopedia Britannica webpage, with additions).

Romania's climate is characteristic of the moderate temperate-continental zone, with an average annual temperature ranging from 4°C to 10°C and mean annual rainfall between 400 mm to 1200 mm. About 1.4 % of the land surface of Romania consists of karst. This low percentage is due to Pliocene and Quaternary deposits which overlie the limestone and dolomite, the predominant karst forming rocks. More than 12,000 caves are known, a part of these are well decorated with speleothems.

Romania's karst can be classified into three categories, characterized by the depth to the karst aquifers and the relationship between the karst aquifer and land surface (open karst hydrogeological system or confined).

1. Deep Karst type features occur in the carbonate rocks underlying non-soluble bedrock and overlain by aquicludes or aquitard deposits (consolidated deposits). These confined aquifers are typical of the Walachian Platform (geological name used for Romanian Plain). The carbonate deposits of Malm-Barremian Ages are 1,500 in thick and cover approx. 25,000 km² of the Walachian Platform.
2. Shallow Karst type features are formed in carbonate rocks overlain by unconsolidated sediments. The thickness of the overburden ranges between 10 to 50 m. This type of karst is found in all parts of Romania, but is most common in Dobruja (Dobrogea), where the overburden is mainly loess. The shallow type karst aquifer is mostly semi confined or unconfined. The average area covered by shallow karst type is approx. 3,500 km².
3. Bare (Exposed) karst occupies about 4,400 km² (Bleahu, 1965) of the Romanian territory (approx. 1.4% of Romania's land surface) and is formed in Paleozoic, Mesozoic, and Neogene deposits. The bare karst type takes into account the rocks on which the karst proper is developed as limestones, dolomites, crystalline limestones, salt and gypsum. The Paleozoic deposits are recrystallized and represent about 16% of the total bare karst area. The Mesozoic deposits belong to two sedimentary cycles (Triassic- 17.8% and Jurassic - Cretaceous 47.3%) and the Neogene deposits to a third cycle (Eocene, Tortonian and Sarmatian - 16.8%) (Bleahu, 1965).

REFERENCES

• Bleahu, M. (1964) Karst of Rumania; Important Karst Regions of the Northern Hemisphere. Elsevier Publishing Company, Amsterdam, Netherlands.
• Bleahu, M. and Rusu, T. (1965) Carstul din Romania. O scurta privire de ansamblu; Lucrarile Institutului de Speologie "Emil Racovită" Tom.IV.
• Bleahu, M., et al. (1976) Pesteri din Romania. Bucuresti: Ed. Stiintifica si Enciclopedica.
• Bleahu, M., et al. (1985) Harta geologica Pietroasa, sc.1:50,000, IGG Bucuresti.
• Encyclopedia Britannica Website
• Sencu, V., et al. (1973) Carstul. Atlasul Republicii Socialiste Romania.