Abrasion coasts

The character of the coastal zone defines the morphology and type of the coasts. In mountainous areas, abrasive coasts dominate. In many cases, they are complicated owing to the development of intensive landslide and caving processes and thus may be referred to as the abrasive-denudational type. In plain and low areas, the coasts are mostly accumulative. Lagoonal and deltaic coasts are confined to the areas near river mouths. 

Abrasive coasts are mostly composed of clayey deposits, poorly-cemented rocks, or limestones. The cliff heights range from 15 to 35 m. The abrasion rate is controlled by the composition of the coastal rocks and the cliff heights. The recession of the cliffs is also caused by the development of landslide and caving processes, especially under the conditions of strong storms. The length of individual sliding blocks reaches 500 m at a width of up to 15 m. Deep surf niches are formed in the lower parts of the cliffs. 

The Tarkhankut Peninsula features abrasive coasts composed of coquina-limestone rocks with high (20-40 m) cliffs, surf niches, and deepened bench. Numerous grottos, abrasive niches, and underwater rocks are attractive for submarine excursions and diving [2]. 

Fig. 5 Coastal and bottom topography of the Aral Sea (according to [2, 24, 25]). Types of coasts (1) abrasion-denudation coasts (2) abrasion coasts with slumps (3) graded abrasion coasts (4) embayed coasts with accumulative landforms (5) graded complex coasts (6) embayed ingression coasts (7) graded accumulative coasts (8) deltaic coasts (9) reed coasts (10) nearshore shallow (0-20 m) (11) central depression (20 0 m) (12) central deep (40-68 m) (13) submarine ridge (ArkhangeTskii Ridge)...

Genetically, the Aralian coasts may be classified into three types, namely, abrasion coasts (modeled by marine erosion), depositional and abrasion-deposition-al ones [25]. Coasts of the first type (abrasion) are most common at the western, northern and part of the southern margins of the sea. They are built of compact calcareous marls and sandy-clayey Paleogene and Neogene rocks. Typically, they form high (up to 200 m) abrasion cliffs with wave-cut notches and a narrow strip of sandy beach. In areas where loose rocks occur, coasts are rather low, with a shallow notch and broader beach. There exist varieties of abrasion coasts, such as abrasion-denudation ones and abrasion coasts with slumps, with material from screes, rockfalls, and slumps present in the nearshore zone in abundance. 

Fig. 1 Topography of the coasts and floor of the Black Sea. Bottom relief 1 shelf a accumulative, b abrasive 2 continental slope a accumulative, b stepwise 3 floor of the basin 4 continental footstep 5 underwater canyons 6 bars a sandy, b marginal 7 morphological boundaries a distinct, b fuzzy. Coast types 1 landslide 2 abrasive 3 abrasive-accumulative 4 accumulative 5 lagoonal 6 deltaic...

The coasts of Odessa Bay represent an abrasive-accumulative arc with beaches in its top part and abrasive areas of capes North Odessa and Langeron at its edges. 

The Turkish coasts of the Black Sea are mountainous and steep over almost their entire extension, they are referred to as the abrasive type. The East and West Pontian mountains, which approach the Black Sea from the south, feature maximum marks of 3937 m (Kachkar Dag), 3439 m (Karchkhal Dag), and 3711 m (Verchennik Tepe). On relatively smooth rectilinear coasts, one can observe an alternation of rocky capes and wide bays that do not penetrate deeply into land. 

In the west, the coasts of Bulgaria are mountainous in their southern part, while in the north, closer to the Rumanian boundary, they give place to the lowlands of the Danube Plain. Nevertheless, the abrasive type dominates over the coasts of this region. The height of the cliff increases up to 60 m near Cape Kaliakra and to 220 m north of the Batov River. The abrasive coastal slopes feature numerous landslides the abrasion rate of these coasts is up to 0.5 m/year [4]. 

In the southeast, the delta of the Kuban River with vast flooded plains and numerous channels extends over about 100 km. The Kuban River enters the top part of the open Temryuk Bay. Low seacoasts gradually descend to a flat sandy bottom. The depths smoothly increase with the distance from the coast. The largest depths are observed in the central part of the sea in Taganrog Bay, they range from 2 to 9 m. In Temryuk Bay, mud volcanoes are known. The main sources for the supply of the terrigenous matter that forms the bottom sediments of the Sea of Azov are represented by the products of coastal abrasion and the riverine alluvium. The bottom sediments are mostly represented by clayey and silty oozes and sands. 

In the last 30-35 years, delta coast has experienced abrasion. The retreat of the delta coastline has consisted of 3-5 myear-1. The main reasons of this process are reduction of the river sediment load after reservoir construction and sea level rise. Slight progradation of the delta is observed only near the mouths of the main branches. 

Significant decrease of the river sediment input to the seas together with the sea level rise and wave action can disturb the sediment balance in the coastal zone and intensify the abrasion and retreat of the sea coasts. 

I recognized right away that I was already a West Coast person because of living for eight years in Vancouver. The abrasive nature of New York and the awful climate in the summer and the somewhat isolated nature... 

Abrasion-depositional coasts form a transitional type they are widely distributed at the northern and south-eastern margins of the sea. They are distinct... 

Erosion is a constant feature of a beachfront. Unconsolidated beach sand can be shifted readily, sometimes spectacularly through great distances over short periods of time, by wave action. Sand, pebbles, and rock in the form of roimded cobbles constantly wear against the coast by wave action, exerting a constant abrasive action called milling. This action is augmented by the chemical weathering effects of seawater, in which the salt content may play a role. 

Paleoseismology of Rocky Coasts, Fig. 6 Abrasion coastal platform uplifted in 1923 at Miura Peninsula. Water level (at Aburatsubo tidal station) is at -76 cm. Spring tidal amplitude is 54 cm (Photo P.A.P. 592, May 1974)... 

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