Select your language

Suggested languages for you:
Log In Start studying!
StudySmarter - The all-in-one study app.
4.8 • +11k Ratings
More than 3 Million Downloads
Free
|
|

All-in-one learning app

  • Flashcards
  • NotesNotes
  • ExplanationsExplanations
  • Study Planner
  • Textbook solutions
Start studying

Coastlines

Save Save
Print Print
Edit Edit
Sign up to use all features for free. Sign up now
Coastlines

Have you ever gone for a stroll on a beach? Swam in the ocean? Gone surfing? Or built a sand castle next to the waves? If you have, then you've been to a coast and walked along a coastline. The Earth has approximately 620,000 kilometres (390,000mi) of coastlines and they are not just a barrier between land and water; they are also important natural ecosystems. Let's take a look at some of the different types of coastlines and their role in our geopolitics and global climate.

Coastline definition in geography

Within geography, the definition of a coastline is the area where land meets water. The water, with an endless supply of waves, whether pounding or gentle ripples, is constantly changing coastlines around the globe.

How coastlines are made and shaped

The extent to which the shape of a beach or coast is created or altered depends mainly on the action of waves upon it. Waves can be gentle and infrequent or more significant, more frequent, and more powerful.

Waves interact with land through three major marine processes: erosion, transportation, and deposition. Over time, waves beating against the shore will wear it down (or erode it). Transportation is the movement of material from a coastline--such as sand and gravel--while deposition is the addition of material to a coastline. These processes are happening constantly and usually work in conjunction to produce coastal features.

Types of coastlines

There are four major different types of coastlines:

  1. Emergent coastlines
  2. Submergent coastlines
  3. Concordant coastlines
  4. Discordant coastlines

Below, we will go into more detail on all of these different types of coastlines.

Emergent coastlines

Emergent coastlines happen when either the water level has fallen or the land has risen. Either way, there is now a (bit of) coastline that is no longer submerged under water. Emergent coastlines can pop up after tectonic activity, where the land is being pushed up by the tectonic plates.

Many emergent coastlines have existed since the glacial phases of the Pleistocene Epoch, which lasted from about 2,580,000 and 11,700 years ago because the sea levels were much lower than they are today.

Emergent coastlines can have features such as marine terraces, relict sea cliffs, sea stacks, and raised beaches. They are, for the time being, out of reach of the current wave action and will therefore not be affected by them.

Submergent coastlines

In contrast with emergent coastlines, submergent coastlines are coastlines submerged under water due to rising sea levels. Many of these types of coastlines were actually formed toward the end of the Last Glacial Period (LGP). The LGP encompasses the period of c. 115,000 to c. 11,700 years ago. During this time, glaciers and ice sheets were retreating, causing a rise in global sea levels and localised changes in land height.

Coastlines are constantly changing, with sea levels rising or falling, and it is no different with submergent coastlines. The rise in sea level can be the result of an increase in water volume or the sinking of the land's surface. The latter can happen when tectonic forces lowered the land level or when river deposits and compaction of alluvial (river) sediments occur.

There are two special types of submerged coastlines: ria coasts and fjord coasts.

Ria coasts

A ria is a drowned river valley that leads out to the sea. Where once there was a simple river with well-defined banks, now there is a sprawling river that has submerged most of the terrain around it. A ria coast hosts multiple rias. There are rias throughout the world, including Poole Harbour in Dorset.

Fjord coasts

Fjords are created when glaciers cut through valleys and are submerged. The results are deep, lengthy, thin inlets surrounded by high cliff faces. A fjord coast hosts multiple fjords. While there are fjords all over the world, the most renowned fjord coasts are in Norway--and in fact, "fjord" is a Norwegian word.

Discordant coastlines

Discordant coastlines occur when bands of different types of rocks run perpendicular (at 90 degrees) to the coast. These bands of rocks alternate between soft rock and hard rock, all eroding at different rates and in varying ways. Because of this difference in erosion resistance, discordant coastlines are home to headlands, due to eroding hard rock, and bays, due to eroding soft rock.

The coastline between Durlston Head and Studland Bay in Dorset, UK, is a great example of a discordant coastline (figure 1). There are different bands of rock that have shaped this discordant coastline, namely:

AreaType of rock
Durlston Headlimestone (hard rock)
Swanage Bayclay and sand (soft rock)
Ballard Point chalk (hard rock)
Studland Bay (and beyond)clay and sand (soft rock)

Coastlines, Approx. locations on the coastline between Durlston Head and Studland Bay, StudySmarter

Figure 1: Approx. locations on the coastline between Durlston Head and Studland Bay, map data: © 2022 Google

The image below (figure 2) is taken at Durlston Head, which shows the bay (yellow) and the headland (red).

Coastlines Durlston Head with its bay (yellow) and headland (red), Dorset, UK StudySmarter

Figure 2: Durlston Head with its bay (yellow) and headland (red), Dorset, UK, Champion/Wikipedia, CC BY-SA 3.0

Fun Fact: if you are interested in dinosaurs and dinosaur fossils, Durlston Bay is a renowned site for Early Cretaceous fossils. The Early Cretaceous, sometimes known as Lower Cretaceous, is the period stretching from 145 million years ago to 100.5 million years ago.

Concordant coastlines

While discordant coastlines have bands of different rock types running perpendicular to the coast, concordant coastlines have bands of similar rock types running parallel (alongside) to the coast. The difference in rock types between discordant and concordant coastlines means that there are differences in erosion. As mentioned earlier, discordant coastlines form headlands and bays; on the other hand, concordant coastlines form coves. These coves are formed by waves breaking through an outer layer of hard rock, such as limestone, and then, over time, the waves sweep away the soft rock further inland, like sand and clay, creating a cove.

A concordant coastline can take one of the following two landform types:

Landform typeExplanation
Dalmatian typeNamed after the Dalmatia region on the Adriatic Sea. Long offshore islands and coastal inlets are running parallel to the coastline.
Haff type These are found in Haffs, also known as lagoons, on the Baltic Sea's southern shores. Long spits of sands run parallel to the low coast, enclosing the coast.

An example of a concordant coastline is Lulworth Cove, again, in Dorset, UK (figure 3). This cove is located near the village of West Lulworth and is one of the best examples of a concordant coastline.

Coastlines, Location of Lulworth Cove, Dorset, UK, StudySmarter

Figure 3: Location of Lulworth Cove, Dorset, UK, map data: © 2022 Google

The outer layers of the coastline, those directly on the waterline, are Portland and Purbeck limestone, and they have been eroded away over many years. After the waves broke through, creating an opening, the softer clay after the limestone started to erode away as well, creating a cove (figure 4). The shape of the cove is the result of wave diffraction.

Wave diffraction happens when the narrow opening to the cove causes the waves to bend, creating an arc shape wave.

Coastlines the process of forming Lulworth Cove, Dorset, UK StudySmarter

Figure 4: the process of forming Lulworth Cove, Dorset, UK, Red/Wikimedia Commons, CC-BY-SA-3.0

The image below (figure 5) shows the narrow opening created in the limestone and the cove that formed afterwards.

Coastlines Lulworth Cove in Dorset, UK StudySmarterFigure 5: Lulworth Cove in Dorset, UK, map data: © 2022 Google


Fun Fact: Lulworth Cove is a World Heritage Site and attracts approximately 500,000 visitors a year. Lulworth Cove is located on the so-called Jurassic Coast, spanning 185 million years of geological history, from the Triassic (252 - 201 million years ago), Jurassic (199.6 - 145.5 million years ago), and Cretaceous (145 - 66 million years ago) periods. The Jurassic Coast is a world-renowned site where you can find geological (natural) features, and different types of fossils, such as dinosaurs and a fossil forest.

Did you know? Concordant coastlines are also called 'concordant longitudinal' or 'Pacific type' coastlines.

Facts about coastlines

Okay, now we know what coastlines are. But do they serve as anything more than a place to go for a hike or a tan? Besides hosting a multitude of specialised plants and animals, coastlines are also critical to our economic and political infrastructures, providing people with sources of food and livelihoods and allowing us to determine where our borders actually end.

Coastal ecosystems

Numerous plants and animals have adapted to live along coastlines. If you've been to the beach, you've probably seen some of them: mangrove trees and hermit crabs, penguins and sea oats- organisms that can neither fully survive way out at sea, nor venture too far inland. Large colonies of sea lions and seals sleep and breed along coastlines, entering the seas to hunt. Sea turtles return to coasts to lay their eggs, and birds like gulls and pelicans do much of their hunting near the shore.

Coastal populations

Humans, too, could almost be classified as a coastal species! Approximately 40% of all people live within 100km of a coastline. Many of our major cities have developed along oceanic coasts as well: think of New York City, Tokyo, Istanbul, Dubai, Hong Kong, and Copenhagen, just to name a few! Even London is built along the River Thames, which flows into the North Sea. This is because access to the coast offers the opportunity for harvesting marine resources, especially fish, as well as the ability to conduct international trade via the sea.

Coastlines as national boundaries

Coastlines also help us demarcate international boundaries. This is important in delineating who has legal, economic, and military jurisdiction in areas along the coast.

In 1982, the United Nations held a Convention on the Law of the Sea (UNCLAS), where maritime (sea) boundaries were established. While not every UN member has ratified UNCLAS, most nations abide by it anyway.

The coastline determines everything. Taking the low-water line along the coast (or, the baseline), UNCLAS put forth the following:

ZoneDistance from baselineNational rights
Territorial waters12 nautical miles (∼22.2km)This is considered sovereign national territory, the same as boundaries on land.
Contiguous zone24 nautical miles (44.4km)Limited law enforcement jurisdiction to prevent crimes related to customs or trafficking.
Exclusive economic zone200 nautical miles (∼370.4km)Unique access to harvest all resources within the EEZ, including fishing and fracking.

Special exceptions apply to areas like straits, where ships can't help but pass through territorial waters. However, overall, access to a coastline can grant a country food supplies and economic resources that land-locked countries cannot acquire without trade.

Coastlines and climate change

As our Earth warms, glaciers melt, causing the sea level to rise. As we mentioned earlier, this tends to shift the coastline further inland. The shifting coastlines can impact freshwater resources near the coasts by creating brackish mixtures, and can also pose an obvious danger to infrastructure built directly along the coast. Many of the major cities built directly along coastlines, such as New York City and Tokyo, will be forced to develop solutions that counter rising sea levels or else abandon waterfront infrastructures and construct further inland.

Additionally, hotter temperatures enable extreme weather events like hurricanes to occur more frequently. As these systems develop at sea, communities along coastlines are the most vulnerable to any potential destruction.

Coastlines - Key takeaways

  • There are four major types of coastlines: emergent, submergent, discordant, and concordant.
  • Emergent coastlines have emerged from the water; submergent coastlines have submerged below the water.
  • Discordant coastlines have bands of different rock types running perpendicular to the coast; concordant coastlines have bands of similar rock types running parallel to the coast.
  • The United Nations uses coastlines to help determine international boundaries at sea.
  • Coastlines will expand as climate change continues.

Sources:

Frequently Asked Questions about Coastlines

The three marine processes that shape the coastline are erosion, transportation, and deposition.

Coastlines are formed through the processes of erosion, transportation, and deposition. Each process can produce several coastal features; however, they often work together to sculpt the coastlines.

The four major types of coastlines are emergent coastlines; submergent coastlines; concordant coastlines; and discordant coastlines. 

A coastline is anywhere where the land meets the water. A unique coastline within the UK is Lulworth Cove in Dorset. 

A coastline is an area where land meets the water. If you've been to the beach, you've been to a coastline!

Final Coastlines Quiz

Question

How are waves produced?

Show answer

Answer

Waves are produced by friction between the wind and water, resulting in an energy transfer from the wind to the sea. Ripples are created; these ripples will become waves if the wind is sustained.

Show question

Question

When do waves move forward?

Show answer

Answer

Waves move up and down – there is no horizontal movement. It is only when the water enters shallower areas that the water itself moves forward.

Show question

Question

What is the highest point of a wave called?


Show answer

Answer

wave crest

Show question

Question

What is the distance between trough and crest called?

Show answer

Answer

The wave height.

Show question

Question

Explain wave refraction.

Show answer

Answer

As a result of the coastal feature, the depth of water around a coast varies. As the wave approaches a coast, its progress is modified due to friction from the seabed, halting the motion of waves. In addition, as waves approach a coast, they are refracted so that their energy is concentrated around headlands but reduced around bays.

Show question

Question

What are the two types of waves?


Show answer

Answer

Constructive and destructive waves.

Show question

Question

Describe a constructive wave.


Show answer

Answer

They are also called spilling or surging waves. They are gentle, flat waves with a strong swash and a weak backwash; as a result, constructive waves build beaches. As the wave breaks, it carries material up the beach in its swash. Beach material is deposited as a bridge of sediment (berm) at the top of the beach. The relatively gentle profile of the beach with a steep ridge at the top of the beach means that the backwash soaks into the sand or slowly drains away. When the following wave breaks, its swash will deposit more material without it being 'captured' by the backwash of the preceding wave.

Show question

Question

Describe a destructive wave.

Show answer

Answer

These waves are also known as plunging waves. Not surprisingly, destructive waves destroy beaches. As the wave approaches the coast, it gains height and drops onto a steep beach. As a result, it does not travel far up it. The swash of a destructive wave is much weaker than its backwash. This means that these waves transport beach material back into the sea, lowering the height of a beach. The more the waves crash onto the beach, the more sediment is washed out to sea. Because the waves are so frequent, the backwash has less time to soak into the sand. During a storm, the most common waves are destructive.

Show question

Question

The following are facts about constructive waves. Add in the missing words

Their wavelength is …….and a….. frequency (8-10 waves per minute).

They have a….... gradient, typically under ………. in height.

They have low ……. and an …... orbit.

Have a larger ……. than ………..

Show answer

Answer

Their wavelength is long and a low frequency (8-10 waves per minute).

They have a low gradient, typically under one meter in height.

They have low energy and an elliptical orbit.

Have a larger swash than backwash

Show question

Question

The following are facts about destructive waves. Add in the missing words.

Destructive waves are usually ……. over 1m.

They have a more ……… .cross profile.

They are most common where …… .. is short.

They have a mainly circular orbit, a …… .. gradient, 

These act as agents of erosion because their ………. is greater than their .......

They are more common in ……. than in summer

Show answer

Answer

Destructive waves are usually very high, over 1m.

They have a more circular cross profile.

They are most common where fetch is short.

They have a mainly circular orbit, a steep gradient.

These act as agents of erosion because their backwash is greater than their swah.

They are more common in winter than in the summer

Show question

Question

There are four processes involved in the eroding coastlines. What are they?

Show answer

Answer

Hydraulic action, attrition, abrasion, and corrosion.

Show question

Question

What is hydraulic action?

Show answer

Answer

This is where waves approach the cliff; air may become trapped and compressed in joints and cracks along a cliff face. Then when the wave retreats, the compressed air expands again. This continual process can weaken the joints and cracks in the cliff, causing pieces of rock to break off.

Show question

Question

What is abrasion?


Show answer

Answer

Bits of rock and sand that the waves have picked up are thrown against the cliff face. The sediment acts as a tool on the cliff, chiselling away at the surface and gradually wearing it down by removing small particles.

Show question

Question

What is attrition?


Show answer

Answer

When a wave breaks upon the shore, rocks and pebbles that are being carried collide with each other breaking them and eventually making them smaller and smoother. The net result is that the sediment gets smaller and smaller over time.

Show question

Question

What is corrosion?


Show answer

Answer

Corrosion is also known as solution. It is where salts and acids within the seawater will gradually dissolve some types of rock found along the coast. This process happens over thousands of years.

Show question

Question

What is a coastline?

Show answer

Answer

An area where land meets water.

Show question

Question

Which of the following is NOT a major process through which waves shape the coast?

Show answer

Answer

Runoff

Show question

Question

Which of the following are major types of coastlines? Select all that apply. 

Show answer

Answer

Concurrent Coastlines

Show question

Question

What is an emergent coastline?

Show answer

Answer

An emergent coastline that "emerges" from the water--either the land has risen, or the water level has fallen. 

Show question

Question

What is a submergent coastline? 

Show answer

Answer

A submergent coastline is a coastline that has submerged below the water.

Show question

Question

True or False: Ria coastlines and Dalmatian landforms are both associated with submergent coastlines.

Show answer

Answer

False! Ria coastlines are a type of submergent coastline, but Dalmation landforms are associated with concordant coastlines.

Show question

Question

What is a discordant coastline?

Show answer

Answer

Discordant coastlines are characterised by different bands of rocks running perpendicular to the coast.

Show question

Question

What are concordant coastlines?

Show answer

Answer

Concordant coastlines are characterised by bands of similar types of rocks running parallel to the coast.

Show question

Question

True or False: Concordant coastlines form coves. 

Show answer

Answer

True!

Show question

Question

Which of the following are associated with discordant coastlines? Select all that apply.

Show answer

Answer

Headlands

Show question

Question

What percent of the global population lives within 100km of a coastline? 

Show answer

Answer

About 40% of the global population lives within 100km of a coastline. 

Show question

Question

True or False: In 1982, the United Nations Convention on the Law of the Sea created international maritime boundaries based on relative naval power.

Show answer

Answer

False! UNCLAS implemented a universal system for maritime boundaries based on baselines, which are measured from the low-water line at the coast. 

Show question

Question

How far out to territorial waters extend from the coast (or baseline)? 

Show answer

Answer

In accordance with UNCLAS, territorial waters extend 12 nautical miles from the baseline. 

Show question

Question

Which of the following is NOT typically found in a coastal ecosystem? 

Show answer

Answer

Mangrove

Show question

Question

​​​​​True or False: As sea levels rise, coastlines are likely to expand. 


Show answer

Answer

True!

Show question

60%

of the users don't pass the Coastlines quiz! Will you pass the quiz?

Start Quiz

Discover the right content for your subjects

No need to cheat if you have everything you need to succeed! Packed into one app!

Study Plan

Be perfectly prepared on time with an individual plan.

Quizzes

Test your knowledge with gamified quizzes.

Flashcards

Create and find flashcards in record time.

Notes

Create beautiful notes faster than ever before.

Study Sets

Have all your study materials in one place.

Documents

Upload unlimited documents and save them online.

Study Analytics

Identify your study strength and weaknesses.

Weekly Goals

Set individual study goals and earn points reaching them.

Smart Reminders

Stop procrastinating with our study reminders.

Rewards

Earn points, unlock badges and level up while studying.

Magic Marker

Create flashcards in notes completely automatically.

Smart Formatting

Create the most beautiful study materials using our templates.

Just Signed up?

Yes
No, I'll do it now

Sign up to highlight and take notes. It’s 100% free.