On the Dynamics of “Almost Equilibrium” Beaches in Semi-sheltered Bays Along the Southern Coast of the Gulf of Finland - The Baltic Sea Basin - page 259

factors (Granö and Roto 1989 ) . The coast largely consists of extremely stable and
very irregular bedrock formations that are mostly stripped of finer sediment. The
presence of such formations gives rise to highly irregular bathymetry, extensive
archipelago areas, and extremely complex geometry of the coastline.
In contrast, the eastern and southern coasts of this gulf were formed and devel-
oped predominantly under the effect of wave action (Orviku and Granö 1992 ) . The
coasts obtained their contemporary shape only a few millennia ago (Raukas and
Hyvärinen 1992 ) . The volume of sediment and the magnitude of littoral drift are
modest. The most common type of coasts here are the embayed coasts which are
straightening with sediment accumulation. The most stable beaches are located in
deeply indented bays.
Most of the sandy beaches along the North Estonian coast overlie ancient dunes
and river deltas. An overview of geology and geological history of the entire Gulf
of Finland area is presented in the collection by Raukas and Hyvärinen ( 1992 ) . The
descriptions of general properties of the beaches at its southern coast are mostly
published in Russian (Orviku 1974 , Orviku and Granö 1992 ) . A shorter review of
the relevant knowledge is given by Soomere et al. ( 2007 ) .
Two distinctive subsections can be distinguished along the North Estonian
coast. Deeply embayed beaches along the northern coast of Estonia (including
Pirita Beach) westwards from the longitude 27 ◦ E reveal many properties of bay
beaches for which waves are generated under the effective fetch distances <50 km
(Nordstrom 2005 ) . They are mostly geometrically sheltered from high waves com-
ing from a large part of the potential directions of strong winds (Soomere 2005 ) .
As a consequence, their local wave climate is relatively mild compared with that in
the open part of the Gulf of Finland or in the adjacent sea areas. For example, the
annual mean significant wave height is as low as 0.29-0.32 m in different sections
of Pirita Beach (Soomere et al. 2007 ) . On the other hand, wave fields at widely open
sections of the coast eastwards from the longitude 27 ◦ E are almost totally governed
by the properties of wind in the open parts of the Gulf of Finland (Laanearu et al.
2007 ) .
The western part of the North Estonian coast can be divided into many small sed-
imentary compartments and isolated beaches of length frequently <1 km (Soomere
et al. 2007 ) separated by rocky peninsulas and headlands. Viimsi Peninsula located
next to Tallinn (Fig. 13.3 ) divides the embayed beaches of the northern coast of
Estonia into two subsets. The features of the coast eastwards from this penin-
sula are mainly related to glacial and fluvioglacial formations and deposits of the
foreklint lowland while the bays westwards (including Tallinn Bay) are mostly
associated with structural blocks and ancient erosional valleys cut into the bedrock
(Orviku and Granö 1992 ) . This division is immaterial from the viewpoint of this
chapter.
The composition of the upper layers of the sand mass in several North Estonian
beaches reveals typical features of bay beaches formulated by Nordstrom ( 2005 ) .
Studies of drill cores extending to a depth of 2.1 m into the sea floor near Pirita
show that in deeper areas (down to depths of 15-20 m), the sampled layer con-
sists entirely of relatively well-sorted material. In contrast, several thin medium-