Coast Types and Processes

The foundation for much of the Coast Formation and Processes Topic is Man and the Ocean, a CD-ROM produced by the Russian Head Department of Navigation and Oceanography (HDNO).

The World's shorelines are almost 500,000 km long. They comprise the natural boundary zone between the land and the Ocean. A variety of shores, the result of the action of various natural processes such as storms, tidal and wind waves and currents, thawing and destruction by ice, outflow of fragmental material by rivers and the work of plants and animals. The large value has The greatest effect depends upon the geological structure of a coastal region, which determines the type stability of rocky materials and their breakdown and removal.

 

Extensive glaciation of continents in the recent geological past have resulted in repeated changes in sea level. During the period of the last glacial maximum (17,000-18,000 years before the present), sea level was 100-120 m lower than it is today. The tongues of glaciers in motion carved out valleys in coastal areas in higher latitudes. The increase in sea level caused by the thawing of glaciers caused inundation of glacial valleys and the formation of deep bays (fjords) in polar regions. In non-glacial areas, the flooded valleys are called 'rias.' Such shorelines are widespread in regions where massive crystalline rocks were removed by erosion caused by tectonic uplift. Waves and swell, and to a lesser degree, currents, not only destroy folded and/or friable rocks on erosion-formed shorelines, but also transport material along them. The transported materials that are eventually deposited in shallow waters form shoals, gravel berms and other forms of deposition. On shallow bottom slopes, the eroded rocks are disintegrated, and are deposited along the coasts. Together, these processes result in an equalisation of the coastline. Biogenic shores are developed from the action of vegetation and animal activities. Such shores are widespread in temperate and tropical climates. Coral-built shorelines common in tropical latitudes, where they combine with the cemented remains of coral, calcareous seaweeds and mollusc shells. When conditions are right, there is a heavy growth of vegetation providing the environment to produce mangrove shores. Mangrove shores are low, swampy areas in tropical zones, where the intertwining of the air roots of mangrove trees trap suspended alluvium (particles of silt and sand) and prevent their moving out to create a depositional shoreline from forming.

 

Shoreline formation on the shores of polar seas occurs as a result of the thermal effect on the air and the water. Intensive mechanical weathering of frozen coastal rocks during formation of shores of the polar seas happens in an outcome of thermal effect of air and water. Intensive weathering of frozen coastal rocks in conditions of low temperatures of the air and water contributes to the productions of screes and slope collapses. As an result of downstream transport of rivers, fragmental materials occupy the shorelines, forming deltas. These are produced mainly in tidal areas and have fan-shaped patterns. Alternately, estuaries are created at river mouths, which are affected by tides but do not have associated deltas. The study of shoreline structure, formation processes and their development over time allows a prediction of coastline changes and depths to be determined. The results of these studies are useful for navigation, hydraulic engineering, construction of near-shore structures and for exploiting the resources in the coastal zones of the seas and Oceans.