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Encyclopedia > Coastal geography

Coastal geography is the study of the dynamic interface between the ocean and the land, incorporating both the physical geography(i.e coastal geomorphology, geology and oceanography) and the human geography(sociology and history) of the coast. It involves an understanding of coastal weathering processes, particularly wave action, sediment movement and weather, and also the ways in which humans interact with the coast. True-color image of the Earths surface and atmosphere Physical geography (also know as geosystems or physiography) is a subfield of geography that focuses on the systematic study of patterns and processes within the hydrosphere, biosphere, atmosphere, and lithosphere. ... Population density by country, 2006 Human geography is a branch of geography that focuses on the study of patterns and processes that shape human interaction with the environment, with particular reference to the causes and consequences of the spatial distribution of human activity on the Earths surface. ...

Contents

Wave action and longshore drift

Port Campbell in southern Australia is a high energy shoreline.
Port Campbell in southern Australia is a high energy shoreline.

The waves of different strengths that constantly hit against the shoreline are the primary movers and shapers of the coastline. Despite the simplicity of this process, the differences between waves and the rocks they hit result in hugely varying shapes. Image File history File links Portcampbellcliffs. ... Image File history File links Portcampbellcliffs. ...


The effect that waves have depends on their strength. Strong, also called destructive waves occur on high energy beaches and are typical of Winter. They reduce the quantity of sediment present on the beach by carrying it out to bars under the sea. Constructive, weak waves are typical of low energy beaches and occur most during summer. They do the opposite to destructive waves and increase the size of the beach by piling sediment up onto the berm.


One of the most important transport mechanisms results from wave refraction. Since waves rarely break onto a shore at right angles, the upward movement of water onto the beach (swash) occurs at an oblique angle. However, the return of water (backwash) is at right angles to the beach, resulting in the net movement of beach material laterally. This movement is known as beach drift (Figure 3). The endless cycle of swash and backwash and resulting beach drift can be observed on all beaches. For other uses, see Beach (disambiguation). ...

Rhossili in Wales is a low energy shoreline.
Rhossili in Wales is a low energy shoreline.

Probably the most important effect is longshore drift (LSD), the process by which sediment is continuously moved along beaches by wave action. LSD occurs because waves hit the shore at an angle, pick up sediment (sand) on the shore and carry it down the beach at an angle (this is called swash). Due to gravity, the water then falls back perpendicular to the beach, dropping its sediment as it loses energy (this is called backwash). The sediment is then picked up by the next wave and pushed slightly further down the beach, resulting in a continual movement of sediment in one direction. This is the reason why long strips of coast are covered in sediment, not just the areas around river mouths, which are the main sources of beach sediment. LSD is reliant on a constant supply of sediment from rivers and if sediment supply is stopped or sediment falls into a submarine canals at any point along a beach, this can lead to bare beaches further along the shore. Image File history File links RhossiliBeach. ... Image File history File links RhossiliBeach. ... Longshore drift (sometimes known as shore drift, LSD or littoral drift) is a geological process by which sediments such as sand or other materials, move along a beach shore. ...


LSD helps create many landforms including barriers, bay beaches and spits. In general LSD action serves to straighten the coast because the creation of barriers cuts off bays from the sea while sediment usually builds up in bays because the waves there are weaker (due to wave refraction), while sediment is carried away from the exposed headlands. The lack of sediment on headlands removes the protection from waves them and makes them more vulnerable to weathering while the gathering of sediment in bays (where longshore drift is unable to remove it) protects the bays from further erosion and makes them pleasant recreational beaches. Barriers is a British television series made by Tyne Tees Television for ITV between 1981 and 1982. ... A spit is a deposition landform found off coasts. ... The bay at San Sebastián, Spain A headland is an area of land adjacent to water on three sides. ... The bay at San Sebastián, Spain A headland is an area of land adjacent to water on three sides. ...

See also: Beach evolution

This article or section does not adequately cite its references or sources. ...

Atmospheric processes

  • Onshore winds blowing "up" the beach, pick up sand and moves it up the beach to form sand dunes.
  • Rain hits the shore and erodes rocks and carries weathered material to the shoreline to form beaches.
  • Warm weather can encourage chemical and biological processes to occur. In tropical areas some plants and animals protect stones from weathering, while others actually eat away at the rocks.
  • Temperatures that vary from below to above freezing point result in freeze-thaw weathering, while weather more than a few degrees below freezing point creates sea ice.

This article is about the sand formations, for other meanings see Dune (disambiguation) Mesquite Flat Dunes in Death Valley National Park In physical geography, a dune is a hill of sand built by eolian (wind-related) processes. ... Weathering is the decomposing of rocks, soils and their minerals through direct contact with the air. ...

Biological processes

In tropical regions in particular, plants and animals not only affect the weathering of rocks but are a source of sediment themselves. The shells and skeletons of many organisms are of calcium carbonate and when this is broken down it forms sediment, limestone and clay. For other uses, see Limestone (disambiguation). ... For other uses, see Clay (disambiguation). ...


Physical processes

The main Physical Weathering process on beaches is salt-crystal growth. Wind carries salt spray onto rocks, where it is absorbed into small pores and cracks within the rocks. There the water evaporates and the salt crystallises, creating pressure and often breaking down the rock. In some beaches calcium carbonate is able to bind together other sediments to form beachrock and in warmer areas dunerock. Weathering is the decomposing of rocks, soils and their minerals through direct contact with the air. ... Beachrock along Réunion island seashore Detail showing fragments of coral and shells Beachrocks are created by the rapid cementation of beach sediments in the intertidal zone which leads to the formation of characteristic synsedimentary lithified structures. ...


Sea level changes

Because the sea level on earth regularly rises and falls due to climatic changes. During cold periods more of the Earth’s water is stored as ice in glaciers while during warm periods it is released and sea levels rise to cover more land. Sea levels are currently quite high, while just 18,000 years ago during the Pleistocene ice age they were quite low. Global warming may result in further rises in the future, which presents a risk to coastal cities as most would be flooded by only small rises. As sea levels rise fjords and rias form. Fjords are flooded glacial valleys and rias are flooded river valleys. Fjords typically have steep rocky sides, while rias have dendritic drainage patterns typical of drainage zones. As tectonic plates move about the Earth they can rise and fall due to changing pressures and the presence of glaciers. If a beach is moving upwards relative to other plates this is known as isostatic change and raised beaches can be formed. The Pleistocene epoch (IPA: ) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the worlds recent period of repeated glaciations. ... Global mean surface temperatures 1850 to 2006 Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming is the observed increase in the average temperature of the Earths atmosphere and oceans in recent decades and the projected... Lysefjorden in Norway A fjord (pronounced FEE-ord or fyord, SAMPA: [fi:3:d] or [faI3:d]; sometimes written fiord) is a glacially overdeepened valley, usually narrow and steep-sided, extending below sea level and filled with salt water. ... RIAS can stand for one of the following: Rias, the plural of Ria, a lower river valley submerged by the sea. ... A glaciated valley in the Mount Hood Wilderness showing the characteristic U-shape. ... The tectonic plates of the world were mapped in the second half of the 20th century. ...

See also: Beach evolution

This article or section does not adequately cite its references or sources. ...

Coastal landforms

Spits

Chesil Beach, an excellent example of a tombolo in Dorset, United Kingdom.

If the coast suddenly changes direction, especially around an estuary, spits are likely to form. LSD pushes sediment along the beach but when it reaches a turn as in the diagram, the LSD does not always easily turn with it, especially near an estuary where the outward flow from a river may push sediment away from the coast. The area may be also be shielded from wave action, preventing much LSD. On the side of the headland receiving weaker waves, shingle and other large sediments will build up under the water where waves are not strong enough to move them along. This provides a good place for smaller sediments to build up to sea level. The sediment, after passing the headland will accumulate on the other side and not continue down the beach, sheltered both by the headland and the shingle. Chesil Beach (left), Fortuneswell (foreground), Portland Harbour and Weymouth (background) from the Isle of Portland, Dorset. ... Chesil Beach (left), Fortuneswell (foreground), Portland Harbour and Weymouth (background) from the Isle of Portland, Dorset. ... Chesil Beach from Fortuneswell Looking west down Chesil Beach by Abbotsbury Satelite view of Chesil Beach (shown blue) and Portland Bill (Landsat image viewed using NASA World Wind software) Portland and Chesil Beach from Abbotsbury Castle A fossil from the far western end of Chesil Beach Chesil Beach (sometimes called... Tombolo at Stockton Island, Ashland County (Wisconsin). ... Dorset (pronounced DOR-sit or [dɔ.sət], and sometimes in the past called Dorsetshire) is a county in the south-west of England, on the English Channel coast. ...


Slowly over time sediment simply builds on this area, extending the spit outwards, forming a barrier of sand. Once in a while, the wind direction will change and come from the other direction. During this period the sediment will be pushed along in the other direction. The spit will start to grow backwards, forming a 'hook'. After this time the spit will grow again in the original direction. Eventually the spit will not be able to grow any further because it is no longer sufficiently sheltered from erosion by waves, or because the estuary current prevents sediment resting. Usually in the salty but calm waters behind the spit there will form a salt marshland. Spits often form around the breakwater of artificial harbours requiring dredging.


Occasionally, if there is no estuary then it is possible for the spit to grow across to the other side of the bay and form what is called a bar, or barrier. Barriers come in several varieties, but all form in a manner similar to spits. They usually enclose a bay to form a lagoon. They can join two headlands or join a headland to the mainland. When an island is joined to the mainland with a bar or barrier it is known as a tombolo. This usually occurs due to wave refraction, but can also be caused by isostatic change, a change in the level of the land (e.g. Chesil Beach). An example of this is along the Holderness coastline. Chesil Beach from Fortuneswell Looking west down Chesil Beach by Abbotsbury Satelite view of Chesil Beach (shown blue) and Portland Bill (Landsat image viewed using NASA World Wind software) Portland and Chesil Beach from Abbotsbury Castle A fossil from the far western end of Chesil Beach Chesil Beach (sometimes called... Holderness is an area of England on the coast of Yorkshire. ...


See also

Many stretches of the coastline of East Anglia, England, are prone to high rates of erosion, as illustrated by this collapsed section of the cliffs at Hunstanton, Norfolk. ... Weathering is the decomposing of rocks, soils and their minerals through direct contact with the air. ... This article or section does not adequately cite its references or sources. ...

References

  • Codrington, Stephen. Planet Geography 3rd Edition (02-Dec-2006) Chapter 8 [1]

  Results from FactBites:
 
Coastal geography - Wikipedia, the free encyclopedia (1320 words)
Coastal geography is the study of the dynamic interface between the ocean and the land, incorporating both the physical geography(i.e coastal geomorphology, geology and oceanography) and the human geography(sociology and history) of the coast.
It involves an understanding of coastal weathering processes, particularly wave action, sediment movement and weather, and also the ways in which humans interact with the coast.
Global warming may result in further rises in the future, which presents a risk to coastal cities as most would be flooded by only small rises.
  More results at FactBites »

 
 

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