Unit 8 Exam Questions Flashcards
(20 cards)
Explain two factors influencing wave height. (6 marks)
Wave height is influenced by multiple factors, with the two most significant being:
Fetch Length
Fetch refers to the distance over which the wind blows uninterrupted across the surface of the sea. The longer the fetch, the more energy is transferred from the wind to the water, leading to larger waves. In open ocean environments with extensive fetch, such as the Atlantic Ocean, waves tend to be higher and more powerful compared to those in enclosed seas, like the Mediterranean, where the fetch is shorter.
Wind Speed and Duration
Stronger winds generate more powerful waves by exerting greater frictional force on the water’s surface. Additionally, the longer the wind blows in a consistent direction (duration), the more energy is transferred, further increasing wave height. For example, during storms or hurricanes, where wind speeds exceed 100 km/h, massive waves with heights of over 10 meters can form.
Suggest reasons for the differences in beach profile between the summer and winter (6 marks)
Wave Energy and Seasonal Variation
In winter, stronger winds generate high-energy waves (destructive waves) that erode the beach, carrying sediment offshore. The steep upper beach profile in winter is due to this erosional action.
In summer, weaker winds produce low-energy waves (constructive waves) that deposit sediment, building up the beach. This results in a wider and more gently sloping profile.
Impact of Wave Type
Winter: Destructive Waves
These waves have a stronger backwash than swash, meaning more sediment is pulled away from the beach than is deposited.
This leads to beach lowering and offshore deposition, forming offshore sandbars.
Summer: Constructive Waves
These waves have a stronger swash than backwash, meaning more sediment is deposited than removed.
As a result, the beach profile is built up and extended.
Sediment Transport and Deposition Patterns
Winter: Strong waves remove material from the beach, leading to offshore sandbars. The profile just offshore becomes less steep as sand accumulates on the seabed.
Summer: Sand that was deposited offshore is returned to the beach, rebuilding the berm (ridge of sediment along the shore).
Effect of Beach Material
Coarse materials such as pebbles or shingle tend to remain on the upper beach, leading to steeper winter profiles.
Finer sand is more easily transported offshore in winter, contributing to a flatter offshore profile.
Suggest two reasons for variations in rates of marine deposition. (6 marks)
Wave Energy and the Shape of the Coast – Simple Explanation
The type of wave affects how much sediment is deposited on the coast.
Constructive waves (low energy):
These have a strong swash (water moving up the beach) and a weak backwash (water going back down).
They push sand and pebbles onto the beach, helping to build it up.
Destructive waves (high energy):
These have a strong backwash, which pulls sediment away from the beach.
They cause more erosion and less deposition.
Sheltered areas (like bays):
Waves lose energy due to wave refraction, so more sediment is deposited.
Exposed areas (like headlands):
Stronger waves hit directly, carrying sediment away, so less deposition happens.
Sediment Supply and Longshore Drift – Simple Explanation
More sediment = more deposition.
Sediment comes from:
Rivers bringing material to the sea
Cliffs being eroded
Offshore sources like sandbars
Longshore drift moves sediment along the coast, carried by the zigzag motion of waves.
What happens when longshore drift is blocked?
Structures like groynes stop sediment from moving.
On the updrift side, more sediment builds up.
On the downdrift side, less sediment arrives, so erosion increases.
Suggest reasons why the type of hard engineering solutions varies along a stretch of coastline. (7 marks)
- Wave Energy and Coastal Exposure – Simple Explanation
Strong waves = strong defences.In places with big, powerful waves, like open coastlines, you need strong structures (e.g. sea walls, rock armour) to stop erosion.
Gentle waves = softer methods.In calm, sheltered areas, you can use things like groynes or adding sand to beaches (beach nourishment) to protect the coast. - Coastal Shape and Sediment Movement – Simple Explanation
Headlands and cliffs get hit hard by waves and need strong protection like sea walls and rock barriers.
Bays and estuaries are more sheltered, so softer defences like breakwaters or planting sand dunes can be used to stop erosion naturally. - Longshore Drift – Simple Explanation
Longshore drift moves sand along the coast.To stop beaches from washing away, groynes (wooden or stone barriers) are built to trap the sand.
If something blocks longshore drift (like a harbour), it can cause erosion further along, so extra sand might need to be added to keep beaches stable. - Land Use and How Important the Area Is – Simple Explanation
Busy or built-up areas (like cities, ports, or tourist beaches) need strong and expensive defences like sea walls to protect people and buildings.
Less developed areas (like farmland or nature areas) may use cheaper options like letting the sea flood some areas (managed retreat) or adding sand to keep the coastline stable. - Cost and Upkeep – Simple Explanation
Expensive defences (like sea walls and offshore breakwaters) are used where the land is valuable and needs long-term protection.
Cheaper defences (like groynes or beach nourishment) are used in less risky areas, but they need regular upkeep to stay effective.
Explain how wave refraction affects the distribution of wave energy. (6 marks)
Wave Refraction at Headlands (Bending of Waves)
When waves move toward the coast, they slow down in shallow water because of friction with the seabed.
Around headlands (rocky areas that stick out into the sea), waves bend because the water is shallower on the sides.
This bending makes the waves concentrate (focus) their energy on the headlands.
As a result, there is more erosion (wearing away of rock) at these points.
Over time, this erosion can form features like cliffs, caves, arches, stacks, and stumps.
Wave Refraction in Bays
In contrast, when waves enter a bay (a curved part of the coast), they meet deeper water and keep more of their speed.
The waves spread out, so the energy is spread over a wider area.
This means there is less erosion and more deposition (dropping of sand and materials).
This builds up landforms like sandy beaches and spits.
Impact on the Coastline
Headlands: Get hit by strong waves, causing erosion. This forms cliffs and wave-cut notches (indentations at the base of cliffs).
Bays: Have weaker waves and more deposition, so beaches form.
Beach shapes: These change with the seasons, depending on the type of waves. Constructive waves build beaches, while destructive waves break them down.
Suggest how geology can influence the landscape of a coastline.
- How Rock Type Affects the Coast
Hard rocks like limestone, granite, and sandstone don’t wear away easily. They form steep cliffs and headlands (high land sticking out into the sea).
Soft rocks like clay, shale, and mudstone erode much faster. This creates bays and inlets (curved areas where the sea cuts into the land).
If the coastline has alternating layers of hard and soft rock (called a discordant coastline), the soft rock wears away first, forming bays, and the hard rock stays behind as headlands.
Example: Swanage Bay in the UK is a great example of this. - How Rock Structure Affects the Coast
Cracks (called joints and faults) in rocks are weak points. Waves can attack these using hydraulic action (water forcing air into cracks) and abrasion (pebbles grinding the rock).
This leads to the creation of caves, arches, stacks, and eventually stumps.
If rock layers are horizontal, they create wave-cut platforms as cliffs slowly erode back.
If the layers are vertical or tilted, the cliffs are usually steep.
Folded rocks make cliffs that look uneven or irregular.
Example: Durdle Door in the UK was formed when waves eroded a line of weakness in the limestone, creating a natural arch. - How Weathering and Mass Movement Shape the Coast
Weathering is the breakdown of rocks by natural processes like:
Freeze-thaw: Water gets into cracks, freezes, and breaks the rock.
Salt crystallisation: Salt left behind by seawater breaks the rock apart.
Biological weathering: Roots from plants or burrowing animals weaken rocks.
These processes make the rocks weaker, so waves can erode them more easily.
Mass movement is when large amounts of rock or soil move downhill. This happens more often in soft rocks and includes:
Rockfalls (chunks of rock break off)
Landslides (whole sections of cliff collapse)
These movements cause the cliffs to retreat over time.
Explain why rates of erosion vary along coastlines. (6 marks)
- Wave Energy and Exposure to the Sea
Destructive waves are strong and have a powerful backwash (when water flows back to the sea), which pulls sand and rocks away. This causes more erosion.
Constructive waves are gentler and bring sediment onto the shore. They help build up beaches and reduce erosion.
If a coastline has a long fetch (a long stretch of open sea where wind blows), waves will be more powerful.
Example: The Atlantic coast gets stronger waves than the Mediterranean coast, so it erodes faster. - Rock Type and Structure
Hard rocks like granite, basalt, and limestone don’t erode easily. They form cliffs and headlands.
Soft rocks like clay, shale, and sandstone erode quickly and form bays or inlets.
Example: The Holderness Coast in the UK erodes 2 metres per year because of its weak boulder clay.
Cracks and layers in rocks (called faults, joints, and bedding planes) are weak points where waves can attack, speeding up erosion. - Coastal Shape and Sediment Supply
Headlands stick out into the sea and get hit by focused wave energy, causing high erosion.
Bays are more sheltered. Waves spread out and lose energy, leading to deposition (building up of sand and material).
Longshore drift moves sand along the coast.
If something blocks it (like groynes), sand builds up on one side, but erosion gets worse further down the coast.
Beaches help protect cliffs by absorbing wave energy, acting like a cushion. - Human Impacts and Management
People build hard engineering structures like:
Sea walls to block waves,
Groynes to trap sand,
Breakwaters to reduce wave energy.
These can help in one area but cause problems in another.
Example: At Mappleton (Holderness Coast), groynes protect the village, but erosion got worse further down the coast.
Dredging (removing sand from the seabed for building or ships) removes natural protection and leads to more erosion.
Explain two reasons why the level of risk to coral reefs varies. (6 marks)
- Climate Change and Warmer Seas
Coral reefs need water temperatures between 23°C and 29°C to stay healthy.
When the sea gets too warm due to global warming, corals become stressed.
They lose the tiny algae (called zooxanthellae) that live inside them and give them food and color.
This is called coral bleaching – the coral turns white and becomes weak.
Some areas, like the Great Barrier Reef in Australia, have had serious bleaching in 2016, 2017, and 2020 due to record high temperatures.
Other areas, like near the Galápagos Islands, sometimes stay cooler because of upwelling (cold water rising to the surface), which protects the coral a bit more. - Human Activities and Pollution
People building along the coast, farming, and tourism bring dirt, chemicals, and waste into the ocean.
This causes eutrophication, where too many nutrients cause algae to grow too fast and block sunlight from the corals.
Fishing practices like using cyanide or explosives (common in parts of Southeast Asia) break the reef and hurt sea life.
Some countries have created Marine Protected Areas (MPAs) – these are safe zones where damaging activities are not allowed.
Examples: MPAs in Belize and the Maldives help protect coral reefs by limiting fishing and pollution.
In places with lots of people, like near Jamaica, reefs often get damaged by pollution.
But reefs in protected places, like the Bahamas, stay much healthier.
Suggest how a spit forms. (6 marks)
- Longshore Drift Moves Sediment Along the Coast
Waves usually hit the beach at an angle because of the prevailing wind direction.
The swash (water going up the beach) moves at an angle, but the backwash (water going back down) moves straight down due to gravity.
This creates a zig-zag movement of sand and pebbles along the coast – called longshore drift.
Over time, this moves sediment sideways, forming a long, narrow feature that sticks out from the land. - Deposition Happens in Sheltered Areas
When the coastline bends or enters a sheltered zone like a bay or river estuary, the waves lose energy.
With less energy, waves can’t carry as much sediment, so they drop it (deposition).
This deposited material builds up over time to form a spit – a narrow strip of land extending out into the water. - Curved Ends Form from Changing Winds and Tides
The end of the spit often becomes curved like a hook.
This happens because:
Winds or waves from different directions push the tip inland.
Tidal currents or seasonal wind changes can also change the way waves hit the spit.
Example: Spurn Head on the Holderness Coast in the UK shows this classic recurved shape. - Plants Grow and Create Salt Marshes
Over time, plants can grow on the spit.
These plants trap more sand and mud, helping to stabilize the spit.
In the calm, sheltered water behind the spit, fine sediments settle.
This can create salt marshes or lagoons, which are important habitats for wildlife.
Suggest reasons for variations of salt weathering. (6 marks)
- Temperature and Evaporation Affect Weathering
Salt weathering happens when salty water gets into the rock. As the water evaporates, it leaves behind salt crystals.
These crystals grow and push against the rock, causing it to crack and break.
In summer, it’s hotter, so more evaporation happens, and more crystals form – this means more weathering.
In winter, it’s cooler, so less evaporation happens, and there’s less weathering.
That’s why the graph (Fig. 4.1) shows higher weathering rates in summer than in winter. - Wave Action Adds More Salt to the Rock
Waves splash salty water onto the rocks all the time, especially at the coast.
Big waves (like during storms) deposit more salt, which leads to more weathering.
In years with more storms, there will be more salt and stronger weathering, especially in summer.
Example: In 1983, the graph shows very high summer weathering – probably because of more intense wave action that year. - Rock Type Affects How Easily It Weathers
Some rocks, like sandstone and limestone, have lots of tiny holes (they are porous), so they absorb more salty water.
These rocks are easily broken by salt crystals.
Other rocks, like granite and basalt, are not porous, so they resist salt weathering better.
If the coast has different rock types, that could explain why weathering changes from year to year. - Humidity and Rainfall Also Matter
In humid (moist) air, especially in winter, there’s less evaporation, so fewer salt crystals grow.
If it rains a lot, the rain can wash the salt away before it turns into crystals.
So, in wet winters, weathering is usually lower than in dry winters.
This helps explain why some years on the graph show lower winter weathering than others.
Explain two factors that account for the loss of coral cover on reefs. (6 marks)
- Climate Change and Coral Bleaching
When the ocean gets too warm, corals become stressed and go through coral bleaching.
This happens when corals push out the tiny algae (zooxanthellae) that live inside them.
These algae give corals their bright color and food through photosynthesis.
Without the algae, corals turn white and become weak.
If the water stays hot for too long, corals can die and the reef will break down.
Ocean acidification (from more CO₂ in the water) also weakens coral skeletons, making them easier to break or erode.
Example: The Great Barrier Reef in Australia suffered major bleaching in 2016, 2017, and 2020, damaging over 60% of the reef. - Human Activities and Pollution
Overfishing and harmful fishing methods like dynamite or cyanide fishing can destroy coral reefs and harm sea life.
Building near the coast and farming cause mud and dirt (sediment) to wash into the sea.
This blocks sunlight, stopping the coral’s algae from making food through photosynthesis.
Fertilizers from farms lead to nutrient pollution, causing too much algae to grow (eutrophication).
The thick algae blocks sunlight and uses up oxygen, suffocating the coral.
Tourism can also harm reefs – boats drop anchors on coral, and people may collect coral or touch it, causing damage.
Example: In Jamaica, coral reefs near busy coastlines have been badly damaged by pollution and unsustainable fishing.
In contrast, protected areas often have healthier reefs.
Explain the formation of coastal saltmarshes. (6 marks)
- Sheltered Areas Help Mud Settle
Saltmarshes form in sheltered coastal areas where waves are weak.
This calm environment lets fine sediment like silt and clay settle out of the water.
Tides move this sediment into low-lying areas, creating mudflats (flat, muddy land).
A process called flocculation helps too — in saltwater, tiny clay particles stick together, making them heavier, so they settle faster. - Plants Help Build the Saltmarsh
When mudflats are in place, pioneer plants like eelgrass and cordgrass (Spartina) start to grow.
These plants trap more mud, which slowly raises the ground level.
As the land gets higher, it’s flooded by the sea less often.
Dead plants break down and add nutrients to the soil, helping more types of plants grow later on. - Creeks and Channels Form Naturally
As the saltmarsh grows, small tidal creeks and runnels (shallow channels) form.
These drain water in and out with the tide.
The creeks also help spread nutrients and sediment, which keeps the saltmarsh healthy and stable over time.
Explain why the rates of erosion and deposition vary along a stretch of coastline. (6 marks)
- Wave Energy Affects Erosion and Deposition
Strong waves (called destructive waves) have a powerful backwash that pulls sand away, causing erosion.
Gentle waves (called constructive waves) have a stronger swash that brings in sand, helping build beaches.
Example: Coastlines facing the Atlantic Ocean have high-energy waves and more erosion, while sheltered bays are calmer and allow sediment to build up. - Rock Type Affects Erosion Rates
Hard rocks like granite or basalt erode slowly and form headlands.
Soft rocks like clay or sandstone wear away faster and form bays.
On discordant coastlines (where hard and soft rocks alternate), the soft rock erodes quickly, leaving headlands and bays.
Example: The Jurassic Coast in the UK shows this clearly with limestone cliffs and clay bays. - Longshore Drift Moves Sediment
Longshore drift is the zig-zag movement of sand along the shore, caused by angled waves.
It can build landforms like spits and bars where sand collects.
Man-made barriers like groynes block this movement, causing sand to build up on one side and erosion on the other.
Example: On the Holderness Coast, groynes trap sand, but areas further along the coast lose sediment and erode faster. - Tides and Sea Level Play a Role
Strong tidal currents can carry sand away, reducing beach growth.
When sea levels rise, low-lying areas suffer more flooding and erosion.
Example: The Mississippi Delta is losing land because of rising seas and the ground sinking (subsidence). - Humans Affect Coastal Processes
Sea walls stop erosion in one place but reflect wave energy, which can cause more erosion nearby.
Beach nourishment means adding sand to the beach to help fight erosion.
Example: Miami Beach in the USA regularly adds sand to protect its coastline from washing away.
Explain the changes to a wave as it approaches the shore. (6 marks)
- Waves Slow Down Near the Shore
In deep water, waves move in smooth circles and don’t touch the seabed.
As waves move into shallow water, the bottom part of the wave drags against the seabed.
This friction slows down the bottom of the wave, but the top keeps moving, making the wave steeper. - Waves Get Taller and Closer Together
As the wave slows down at the base, the top bunches up, making the wave height increase.
At the same time, the waves get closer together – this means the wavelength gets shorter. - Waves Become Unstable and Tip Forward
The top of the wave moves faster than the base, so the wave gets steeper and steeper.
When the wave becomes too steep (height is more than 1/7 of its length), it becomes unstable. - The Wave Breaks and Releases Energy
Eventually, the top of the wave falls forward and the wave breaks.
The way a wave breaks depends on how steep the beach is:
Spilling waves: On gentle slopes, the wave breaks slowly and gently rolls forward.
Plunging waves: On medium slopes, the wave curls over and crashes down.
Surging waves: On steep slopes, the wave doesn’t break fully, but rushes up the beach quickly. - Swash and Backwash Move Sediment
After breaking, the water moves up the beach as swash, and back down as backwash.
This movement carries sand and pebbles, shaping the beach.
Constructive waves (with strong swash) build up beaches.
Destructive waves (with strong backwash) erode them.
Explain two factors that might influence rates of erosion along coastlines. (6 marks)
- Coastal Geology and Rock Resistance
Hard rocks (e.g., granite, basalt, limestone) resist erosion, forming cliffs, headlands, and wave-cut platforms.
Soft rocks (e.g., clay, shale, sandstone) erode quickly, forming bays, inlets, and retreating shorelines.
Geological structure, such as joints, bedding planes, and faults, also affects erosion rates.
Example: The Holderness Coast (UK), composed mainly of soft boulder clay, experiences one of the highest erosion rates in Europe (~2m per year), while the limestone cliffs of Dorset erode much more slowly. - Wave Energy and Fetch
Wave energy depends on fetch (the distance wind travels over open water)—a longer fetch results in stronger waves and increased erosion.
Destructive waves (high-energy waves) have a strong backwash, removing sediment from the shore and promoting erosion.
Constructive waves (low-energy waves) have a stronger swash, allowing sediment deposition and reducing erosion rates.
Example: The Cornish coastline (UK) experiences strong wave action due to its long fetch from the Atlantic Ocean, leading to severe cliff erosion.
Suggest two reasons why coastlines lose or gain land. (6 marks)
- Erosion vs. Deposition Balance
Erosion removes land when waves, currents, and tides carry sediment away. This happens in high-energy environments where destructive waves dominate.
Deposition increases land when sediment accumulates in low-energy environments, where constructive waves allow material to settle.
Example: The Holderness Coast (UK) experiences severe erosion (~2m per year) due to its soft boulder clay, while Spurn Head (a spit) is formed by deposition of sediment carried by longshore drift. - Sea-Level Change and Human Activities
Rising sea levels cause land loss, particularly in low-lying coastal areas, by increasing coastal flooding and submersion.
Coastal engineering (e.g., groynes, seawalls, beach nourishment) affects sediment movement—some areas gain land, while others experience erosion.
Example: Miami Beach (USA) undergoes beach nourishment, increasing land area, while the Maldives loses land due to rising sea levels.
Suggest two reasons for variations of erosion rates along a barrier island
- Wave Energy, Longshore Drift, and Coastal Morphology
Higher erosion rates are typically found in exposed areas where wave energy is strong, particularly in regions facing a long fetch.
Longshore drift moves sediment along the coastline, leading to variations in erosion and deposition—some areas gain sediment, while others lose it.
Coastal configuration (e.g., headlands, bays) affects wave refraction, influencing where erosion or deposition occurs.
Example: The Holderness Coast (UK) experiences rapid erosion due to longshore drift, while sediment deposition occurs at Spurn Head spit. - Human Activities and Coastal Management
Sea walls, groynes, and breakwaters alter natural sediment movement, reducing erosion in protected areas while increasing it in unprotected zones.
Harbor developments and dredging may disrupt sediment supply, contributing to localized erosion.
Vegetation loss (e.g., mangroves, dune plants) reduces coastal stability, making erosion more severe.
Example: In Lagos, Nigeria, coastal defenses have altered natural sediment transport, leading to uneven erosion rates along the shoreline.
Explain the formation of a tombolo
- Wave Refraction and Reduced Energy Behind the Island
When waves approach an island, they bend (refract) around it due to the shallower water near the island.
This wave refraction creates a zone of reduced wave energy behind the island, leading to low-energy conditions where sediment can settle. - Longshore Drift and Sediment Deposition
Longshore drift transports sediment along the coastline, moving sand and shingle parallel to the shore.
In areas where wave energy decreases (e.g., behind an island), the transported sediment is deposited, forming a narrow spit extending towards the island. - Formation of a Fully Developed Tombolo
If sediment deposition continues, the spit eventually connects the island to the mainland, forming a permanent or semi-permanent tombolo.
Some tombolos remain permanently above sea level, while others may be submerged at high tide (submerged tombolo).
Explain why sand dunes occur on some coastlines. (6 marks)
- Availability of Dry Sand
A wide, sandy beach is essential for dune formation, providing a source of sand.
Tidal action and wave movement expose sand to the sun, allowing it to dry.
Example: The Oregon Dunes (USA) formed due to continuous sand deposition and wind transport inland. - Strong and Consistent Onshore Winds
Prevailing onshore winds move dry sand inland, initiating dune formation.
The strength of the wind determines how much sand is transported and deposited.
Example: The Namib Desert coastal dunes are shaped by strong trade winds from the Atlantic Ocean. - Obstacles for Sand Deposition
Sand needs an obstacle (e.g., vegetation, rocks, driftwood) to reduce wind speed and encourage deposition.
Over time, sand accumulates around these obstacles, leading to the growth of dunes.
Example: In Studland Bay, UK, marram grass helps stabilize dunes by trapping windblown sand.
Explain the variation between summer and winter beach profiles
- Summer Beach Profile (Constructive Waves)
Constructive waves dominate during summer, characterized by low wave energy and a strong swash.
These waves push sand up the beach, forming berms (ridge-like features of deposited sand) at the high tide mark.
The gentle slope of the summer beach is due to deposition exceeding erosion.
Example: The beaches of the Mediterranean expand in summer due to low-energy waves depositing material. - Winter Beach Profile (Destructive Waves)
Destructive waves dominate in winter, characterized by high wave energy and a strong backwash.
These waves erode the upper beach, dragging sediment offshore and forming offshore sandbars.
The beach profile is steeper near the waterline but lower overall, with limited sand above the high tide mark.
Example: The North Sea coastline (UK) experiences significant winter erosion due to storm activity.
