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Coasts Geography

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Coasts Geography

The coast is a strip of land bordering the sea. It's ever-changing and diverse because constant wave action means that nothing can stay the same for long. Breakers erode cliff faces while the sand is continually being moved up and down the beach. Even on a calm, quiet day, the smallest ripple across a beach will change the coastline.

Waves crashing

Waves

The coastline is shaped by the interaction between the wind and waves. The wind builds up energy in waves far out at sea, and this energy then breaks on the shore, with two types of waves sculpting the coastline in new ways. The two types are constructive and destructive waves. A constructive wave is a strong upward rush of water, known as a swash, which delivers sand and gravel up the beach. A destructive wave is a wave that has a weak swash but a strong backward rush, known as a backwash, which carries the sand and gravel out to sea. Waves hit the beach from one side or the other and return at a right angle to the beach, creating a zigzag motion that moves sand and gravel along the shore.

Deposition and transportation

The ebb and flow of the tides create depositional landforms, such as narrow spits, offshore bars and tombolos, cuspate forelands, and sand dunes. Sediment from muddy rivers and streams maintains the process of coastal construction. There are four main processes involved in the transportation of the sediment:

  • Solution – Substances are dissolved and carried along in the water.
  • Saltation – Larger particles are too heavy to be carried, so they are bounced along the sea bed.
  • Suspension – This is where very fine material is carried along in the water.
  • TractionVery large particles are pushed along the sea bed by the force of the water.

The transportation of sediment along the shore is known as longshore drift or littoral drift.

Erosion

The constant pounding of waves wears away at the base of cliffs, forging platforms and making chunks of rock crumble into the sea. This is known as mass movement. The solid rock eventually breaks away, and the waves scoop out the weaker clays left behind, creating a bay or cove. Headlands are formed where the coastline gives way on either side. This leaves stacks and stumps.

The waves erode the coast in a number of ways, through:

  • Hydraulic Action – Air in cracks in the cliff is compressed when waves crash in. The pressure caused by this action breaks off pieces of rocks.
  • Attrition – Pieces of rock in the water bash against each other and break into smaller bits.
  • Abrasion – Rock and sediment is transported by the waves, smashing and grinding against rocks and cliffs. This breaks bits off and smoothes the surface.
  • Corrosion – Soluble rocks get gradually dissolved by seawater.

Weathering

Along with the marine forces, sub-aerial processes (land-based) help to alter the coast. These can be broken down into weathering, the gradual breaking down of rocks in situ, to mass movement, which is the movement of material downslope through gravity.

Coastal systems

The steady supply of building material via what is known as the coastal system (it has inputs, outputs, stores, and transfers) to the littoral zone (the area of shoreline from the sea to the land) is how this ever-changing coastal landscape is achieved. The coastline can be classified according to its formation process (primary and secondary) as a result of sea-level changes (submergent and emergent) or as a result of plate activity (primary and secondary).

The coast can be steep cliffed (rocky coastline) to relatively flat (coastal plain) depending on if the waves are high or low energy. The geological structure has a massive influence on the morphology (for example, strata, the different layering of rocks) and erosion rates of a coast.

Structure

Rapid coastal erosion is caused by geological factors such as lithology (soft rock type, weak cohesive bonds, and porous rocks) and geological structure combined with marine factors that quickly remove collapsed sediment, allowing erosion to restart.

Long term sea-level changes occur as a result of a complex interplay of eustatic (the rise and fall of the sea levels which are influenced by the ice age), tectonic (where the land sinks or rises because of changes at tectonic plates boundaries), and isostatic changes (these refer to changes in the level of the land which is also influenced by the ice age).

Coastal Management and Engineering

Coastal management (such as hard and soft engineering) disrupts the sediment cells. Human activity, such as the construction of major dams or dredging along the coastline, interrupts the operation of the sediment cell. This can increase rates of coastal recession. Economic and social issues arise where the coast has eroded (on the U.K. Holderness coastline, a holiday park lost over 400-holiday homes through coastal retreat).

Coastal flooding

Coastal flooding is largely a natural event. However, human influences on the coastal environment can exacerbate this. Engineered protection structures along the coast, such as a seawall, alter the natural processes of the beach, often leading to erosion on an adjacent stretch of the coast which also increases the risk of flooding. Sea level changes and the extreme weather caused by climate change have increased the intensity and occurrences of coastal flooding.

Coasts Geography Flood Gate StudySmarterFlood gate

Coasts - Key takeaways

  • Coasts are an ever-changing, diverse place.
  • Waves are the busiest sculptors on the coastline.
  • The three marine processes that affect the coast are erosion, transportation, and deposition.
  • There are four processes by which eroded material is moved, solution, saltation, suspension, and traction.
  • There are four processes by which waves erode the coast, hydraulic action, attrition, abrasion, and corrosion.
  • Rapid coastal erosion is caused by geological factors such as lithology and geological structure combined with marine factors.
  • Long-term sea-level changes occur as a result of a complex interplay of eustatic, tectonic and isostatic changes.

Frequently Asked Questions about Coasts Geography

The coast is a narrow strip of land which borders the sea, it's an ever-changing diverse place.

The coastline is changing due to a number of factors. Waves are the busiest marine sculptor of a coastline. There are two types: constructive and destructive. Depending on which has the greatest influence will determine if depositional features such as a spit or tombolos occur or if the coast is being eroded to produce features such as a cave, stack, or stump. At the same time, there are land-based factors at play such as weathering and mass movement, that affect the coastline and features that are produced.

Geological factors such as lithology (soft rock type, weak cohesive bonds, and porous rocks) and geological structure (jointed rocks, rocks with seaward dipping beds, and heavily faulted rocks) combined with marine factors (longwave fetch promoting large, destructive waves, strong longshore drift) that quickly removes collapsed sediment allowing erosion to restart, along with weather conditions (freezing temperatures and heavy rain increase weathering and the rate of erosion) all affect coastal change

Humans change coasts through the introduction of coastal management, either hard and soft engineering structure, this causes a disruption to the sediment cells. Also through their activity, the construction of major dams or dredging along the coastline, which can increase rates of coastal recession by interrupting the operation of the sediment cell.

It is a section of coastline which has a range of features dependent on where erosion or depositional factors are at play. It will be different from a neighbouring coastline as the dominant factors will have changed.

Final Coasts Geography Quiz

Question

There are two types of waves, what are they?

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Answer

Constructive waves - which has a strong upward rush of water, swash, delivers sand and gravel up the beach, and destructive waves - which has a weak swash but a strong backward rush, backwash.

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Question

Give an example of depositional landforms forms?

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Answer

Narrow spits, offshore bars and tombolos, cuspate forelands, and sand dunes.

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Give an example of coastal features formed as a result of erosion?

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Headland, bays, caves, stack, stumps, and wave cut-platform.

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Question

There are four main processes involved in the transportation of the sediment, what are they?


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Answer

Solution - Substance that is dissolved and carried along in the water.

Saltation - This is where larger particles are too heavy to be carried so are bounced along the sea bed. 

Suspension - This is where very fine material is carried along in the water.

Traction - Very large particles are pushed along the sea bed by the force of the water.


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Question

What are the two types of waves?

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Answer

  1. Destructive
  2. Constructive

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Question

True or False: The presence of a reef offshore is likely a reason for a low-energy coastline.

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Answer

True

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Question

What region has the world’s longest fjord?


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Greenland

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Question

Which type of action is NOT involved in the erosion of sea cliffs?


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Answer

Attention

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Question

Name some types of depositional landforms.

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Answer

  • Simple/compound spits
  • Tombolos
  • Barrier islands
  • Barrier beaches
  • Offshore bars
  • Sand dunes

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Question

True or False: Estuaries form along emergent coastlines

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Answer

False

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Question

Which one of the following is NOT a type of submergent coastline?

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Raised platform

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True or False: Active coasts occur far away from a plate boundary.

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False

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Question

What is it called when the land rises after being compressed by glaciers?

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Answer

Isostatic rebound


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Question

Do longshore currents run parallel or perpendicular to the coast?

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Answer

Parallel

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Question

What process creates round sand particles?


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Attrition

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How many kilometres of coastline are there in the world?


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620,000 km

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Which of the following factors does NOT affect the action of waves on coastlines?


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Cavitation

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What three general types of area contribute material to coasts?


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  1. Inland
  2. Local areas
  3. Plate tectonics 

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What two main activities influence primary coastlines in the long term?


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  1. Climate  change
  2. Plate  tectonics 

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 Steep cliffs are generally found in what type of environment?

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Steep cliffs are generally found in high energy environments.

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Gently, cliffs are generally found in what type of environment?

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They are generally found in a low-energy environment.

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There are two main types of cliffs: what are they?


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They are marine erosion and sub-aerial processes dominated.

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Explain what a Marine erosion-dominated cliff is.


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These cliffs tend to be steep, unvegetated and there is little in the way or rock debris at the base of the cliff; this is because it is quickly broken up by the waves and carried away. Cliffs that are not actively eroded at their bottom by waves will have shallower, curved profiles and low relief.

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Explain what a sub-aerial dominated cliff is.


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On these cliffs, the sub-aerial processes of surface runoff erosion and mass movement (landslides) slowly move rock and sediment downslope; the limited amount of marine erosion means that it will not be removed.

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Question

What features can be found on a rocky coastline?


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Headlands, Cliffs, Wave cut platform (Shoreline platform).

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There are two types of beaches. What are they?


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Swash Aligned Coasts and Drift aligned coasts.

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Question

Names some of the features associated with a sandy coastline.


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Spits and tombolos, Bars and barrier beaches, Offshore bars, and Sand dunes.

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Complete the following sentence. Offshore bars are where deposits of sand and shingle have situated some distance from a coastline; these usually lie ……… sea level, becoming visible only at …...... tide.


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Offshore bars are where deposits of sand and shingle have situated some distance from a coastline; these usually lie below sea level, becoming visible only at low tide.

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Describe what a spit and tombolos are.


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 Spits and tombolos are long, narrow stretches of sand or shingle that protrude into the sea or across an estuary.

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Name three critical elements of geological structure.

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Strata, deformation, and faulting.

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Strata refer to what?

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The different layers of rocks within an area and how they relate to each other.


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Add the missing words. Deformation is the degree to which rock units have been deformed, either by _____ or folding, by _____ activity.


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Deformation is the degree to which rock units have been deformed, either by tilting or folding, by tectonic activity.

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Geological structure types produce two dominant types of coasts. What are they?


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Answer

Concordant and discordant coasts.

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Complete the sentence. Concordant coasts form if the rock layers are running _____ to the coast.


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Answer

Concordant coasts form if the rock layers are running parallel to the coast.

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A concordant coast is also known as what?


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Answer

Pacific coast.

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Question

What is a haff coast?

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Answer

Haff coasts are another type of concordant coast, e.g., the southern fringes of the Baltic Sea. Long sediment ridges topped by sand dunes run parallel to the coast just offshore, creating lagoons (haff) between the ridge and the shore.

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Question

Complete the sentence. Where bands of different rock types run _____, you will see a discordant coastline.


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Answer

Where bands of different rock types run perpendicular to the coast, you will see a discordant coastline.

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What is another name for a discordant coast?


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Answer

Atlantic coast.

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Question

What is a prominent feature of a discordant coastline, and why?


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Headlands and bays. This is due to the rocks’ differing resistance to erosion. A hard rock type, which is resistant to erosion, will create a point of land that extends out into the sea, a promontory. A softer rock type is easily eroded, creating a bay.

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What does dip mean when referring to a cliff profile?

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Answer

When referring to a cliff profile, dip means the angle of the rock strata in relation to the horizontal. For example, sedimentary rocks are formed in horizontal layers but can be tilted by tectonic forces.

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What are joints? 


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Fractures in rocks created without displacement. They occur in most rocks, often in regular patterns, dividing rock strata into blocks with a normal shape.

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Explain what faults are.

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Major fractures in the rock caused by tectonic forces; the rocks on both sides of the fault line will be shifted due to tectonic forces. They represent a significant weakness within the rock layer. 

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Question

Waves are responsible for shaping the coastline. There are two types: what are they?

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Answer

Constructive and destructive waves.

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What are the characteristics of a constructive wave?

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Answer

They have a low frequency and a weak backwash.

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What are the characteristic of a destructive wave?

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They are high and deep, have a high frequency and they have a strong backwash and a weak swash.

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Question

Erosional coastal formations include what?

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Headlands and bays, Cliffs and wave-cut platforms, Stacks and stumps, and Shoreline platforms

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Depositional coastal formations include what? 


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Spits, beaches, offshore bars and tombolos, cuspate forelands, salt marshes, estuarine mudflats, and sand dunes.

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Question

There are four processes whereby the waves transport material; what are they?


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Answer

Solution, saltation, suspension, and traction.

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Question

Add the missing words to the following sentences.  

Solution  - Substance that is ……….. and ………... along in the water.

Saltation  - Larger particles are ………. to be carried, so they are ……….. along the sea bed. 

Suspension  - This is where very ……….. is ……….. along in the water.

Traction  - …………. particles are ………… ... the sea bed by the force of the water.


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Answer

Solution - Substance that is dissolved and carried along in the water.

Saltation - Larger particles are too heavy to be carried, so they are bounced along the sea bed. 

Suspension - This is where very fine material is carried along in the water.

Traction - Enormous particles are pushed along the sea bed by the force of the water.

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Question

What are the main sub-aerial processes?

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Answer

The main sub-aerial processes are weathering and mass movement.


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