TRANSFORMATION OF ISLAND IN PENINSULA IN THE REGION OF THE TOWN OF POMORIE (E BULGARIA)

M. MATOVA Geological Institute, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria e-mail: [email protected]

The town of Pomorie is situated in the central also by the periodicaly occured strong sea erosion. part of the wide Bourgas bay. It is 21 km to NE The constant erosion is of limited influence. Its of the town Bourgas. Now the town is developed effects are located generally to the E and to the S of over the small Pomorie peninsula (3 km in length, the Pomorie lake. The strong erosion, going up to 1 km in width, 5-7m in height). It is correctly to the partial barrier’s destruction, is due to the every mark that the old town of Pomorie was placed only 4-5 years repeated sea storms. The barrier’s over a small island. The town has very rich destruction is realized mainly in the northern part of political, economic and cultural history. Later, the lake’s coast. The town Pomorie is transformed the island was connected with the coast by two sand into island during the cited periods. Several of the barriers (tombolo). The Pomorie lake-laguna (6 km secondary transformation of the peninsula in an in length, 0.8-1.8 km in width, 1.5 m in depth and island are marked in the historic documents. The with 60-80% salinity) is placed between the two summary effect of the sand barrier’s destruction is barriers (30-200 m in width). So the island was of value of 12 mm/a (Marinski, 1998). The negative transform in a peninsula as a result of the vertical epirogenic movements of value up to 2 development of the barriers. The recent town and mm/a are established in the Bourgas bay. The sea the railway were built over the island, the sand level is rising with barriers and the coast. The Pomorie lake is used for an average values of 3.0 mm/a (Marinski., 1998) in the salt production and the mud-curing. The town the second half of the the 20th century, despite has a famous balneological center. Its wines and sea the above mentioned epirogenic subsidence. Some salt production is reputed in their high quality. of the antique parts of the town are covered by The Sarmatian calcareous sands are represented the sea water now. The tectonic, including in the Pomorie island. Two Quaternary sand the seismic activity of the territory is not barriers are located mainly to the N and considerable. The local seismic events could be of a the NW of the island. The cited barriers had realize maximal magnitude value M<5.0 (Bune et al., the connection between the island and the coast. So 1982). the Pomorie peninsula was formed. It could be The recent geoenvironment conditions could be interpreted as a result of constructive tendencies characterized by a general constructive tendency of the development. The peninsula is a Quaternary and by several secondary destructive ones. structure. It is subjected mainly to the sediment The intensive sedimentation and the evolution accumulation. Now there are a permanent of the sand barriers (tombolo) are very important sedimentation over the sand barriers and the coast. for The quantity of the sand is very considerable. the development of the town in the past, now and in The Quaternary formed peninsula structure is not the future. The destruction of the sand barriers is well stabilized. of a relatively limited significance and of a The peninsula is subjected also to the destrucive temporal manifestations. The cited effects needs processes. The destructive processes are special attention and technogenic activity. represented by the sea erosion, the changes of the The long-term stability of the town and sea level, the epirogenic and the tectonic the peninsula in the future is problematic, if the rise movements. of the sea level will be prolonged. The protection The cited barriers are transformed and partially of the town of Pomorie and the Pomorie peninsula destroyed by the constant and small sea erosion, is of national and international significance.

REFERENCES

Bune, B.I., Vuchev, V.T., Gitis, V.G. & Mironov, Marinski, J. (Edit.-in-Chief). 1998. Protection and M.A. 1982. Application of the interval expert long-term stabilization of the slopes of the evaluation approximation method to Black Sea coasts. Acad. Publ. House “Prof. M. compilation of M max maps of Bulgarian Drinov”, Sofia , 199 p. earthquakes. - Geologica Balcanica, 12,2, p. 49- 70.

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