Artificial Structures and Shoreline of Estonian SSR

9. ESTONIAN SSR E. Martin and K. Orviku Institute of Geology Estonia Boulevard Academy of Sciences Tallinn 200101 Estonian SSR INTRODUCTION The Estonian coastal zone developed over the last 10,000 years by the progradation and accretion of sediments caused by various transgres-sions and regressions of the Baltic Sea. The length of the Estonian coastline is about 3,780 km, of which 1,240 km of the shoreline is continental, and 2,540 km is insular. Its boundaries include the West-Estonian Archipelago (Vainameri), and a number of islands in the Gulf of Finland and the Gulf of Riga. In all there are approximately 1,500 islands and islets near the shore and the whole coast is deeply indented with many bays, inlets, and straits. Since the late-glacial period the shoreline of Estonia has changed continuously because of eustatic changes in sea level and the neotectonic uplift of the earth's crust. Geomorhological data indicate that in the postglacial period northwest Estonia has risen about 100 m, and it continues to rise 2 to 3 mm/yr (Vallner et al. 1975). This has exercised a great influence on the structure and development of Estonian coasts. Although during the Pleistocene the territory of Estonia was covered several times by continental ice, in the coastal zone Quater-nary deposits are of insignificant thickness, and in places they have been completely washed away. Glacial landforms have been largely transformed by marine geological processes. Estonian coasts emerged from the sea gradually during the postglacial period and are charac-terized above all by a surface topography produced by the action of the sea: abrasional and accumulative plains, terraces, beach barriers, and spits, among others. High, longitudinal dune ridges near and at some distance from the present shoreline are coastal forms that also mark different stages of the Baltic Sea (Fig. 1). The Estonian coast can be classified as a straight abrasion-ac-cumulation-embayed type of coast, comprising the following subtypes: cliffs, scarps, rocky, and morainic coastal zones (all regarded as abrasional); and shingle sandy and silty coastal zones (regarded as aggradational) (Orviku 1974).