Coastal Processes & Landforms (Cambridge (CIE) IGCSE Geography): Flashcards
Exam code: 0460 & 0976
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Define the coast.
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Define the coast.
The coast is the area where land and sea meet, shaped by marine and terrestrial processes.
How do soft and hard rocks influence coastal landscapes?
Coastlines of soft rocks (sands and clays) are easily eroded to form low, flat bays and beaches, while harder rocks erode slowly to form rugged headlands.
What is hydraulic action in marine erosion?
Hydraulic action is the sheer force of waves hitting the coast, compressing air in cracks and weakening the rock.
What is attrition and why does it not directly erode the coast?
Attrition is when material carried by waves collides and breaks into smaller, smoother pieces, creating sand and shingle rather than wearing away the coastline itself.
Distinguish between abrasion and corrosion in marine erosion.
Abrasion (corrasion) is when waves hurl rock fragments at cliffs, scraping them away, while corrosion (solution) is when slightly acidic seawater dissolves rock, especially limestone and chalk.
Explain how longshore drift moves material along a beach.
Waves approach at an angle due to the prevailing wind, so the swash moves material up the beach at that angle, while the backwash returns it at 90°, creating a zig-zag movement along the shore.
How can blocking longshore drift affect areas farther down the coast?
Blocking longshore drift deprives down-drift areas of sediment, leading to smaller beaches, loss of tourist income and reduced natural coastal protection.
How do constructive waves cause deposition on a beach?
Constructive waves have strong swash that carries sediment up the beach, where the largest material is deposited high on the shore as backwash loses water and energy, sometimes forming features like a berm of shingle.
What three factors affect the height and strength of a wave?
The fetch, the length of time the wind blows, and the strength of the wind. The greater each is, the larger the wave.
How are waves formed?
Waves are formed by winds blowing over the surface of the sea.
In a wave, what are the swash and the backwash?
The swash is the movement of water up the beach; the backwash is the return movement down the beach.
What are the two types of wave, and what does each do?
Constructive waves build beaches (beach builders), while destructive waves erode the beach.
State three characteristics of a constructive wave.
Any three of: a long wavelength with low height; a low frequency of 6-8 per minute; a shallow gradient; low energy; a strong swash that deposits a gently sloping, sandy beach.
State three characteristics of a destructive wave.
Any three of: a short wavelength with high height; a high frequency of 10-12 per minute; a steep gradient; high energy; a strong, abrasive backwash that forms steep, shingle beaches.
What is wave refraction?
As waves enter shallower water near the coast they slow and bend (refract) to fit the shape of the shoreline, focusing energy on headlands so they erode more than the bays.
Why does a constructive wave build up a beach?
Its strong swash carries material up the beach and deposits it, while its weak backwash removes little, so sediment builds up.
True or False?
Destructive waves have a low frequency of 6-8 waves per minute.
False.
Destructive waves have a high frequency of 10-12 waves per minute. It is constructive waves that have a low frequency of 6-8 per minute.
True or False?
A constructive wave has a stronger swash than backwash.
True.
A constructive wave has a strong swash that carries material up the beach and a weaker backwash, so it builds up the beach.
The height and strength of a wave depend on the strength of the wind, the length of time the wind blows, and the _.
The height and strength of a wave depend on the strength of the wind, the length of time the wind blows, and the fetch.
How does rock type affect how quickly a coastline erodes?
Softer rocks such as sands and clays are more easily eroded, while more resistant, harder rocks take longer to erode and produce rugged landscapes.
Contrast the cliff shape of hard rock and soft rock coastlines.
Hard rock cliffs are high and steep with a bare, rugged face; soft rock cliffs are generally lower and less steep with a smoother face showing slumping.
______ and faults expose rock to erosion and weathering along the coastline.
Joints and faults expose rock to erosion and weathering along the coastline.
How does geology determine the coastline vertically and horizontally?
Vertically through the height and profile of a cliff; horizontally through the formation of bays and headlands.
Define a concordant coastline.
A coastline made of the same rock type running parallel to the sea, causing even rates of erosion; it typically produces coves.
At Lulworth Cove in Dorset, which rock runs parallel to the sea, and what lies behind it?
More resistant Portland Limestone runs parallel to the sea, with less resistant Purbeck Limestone and Wealden Clay behind it.
How did the cove at Lulworth form?
Water broke through at weaker points in the resistant Portland Limestone, then eroded the less resistant rock behind.
Define a discordant coastline.
A coastline with alternating bands of rock perpendicular (90°) to the sea, causing uneven rates of erosion; it forms headlands and bays.
On a discordant coastline, alternating bands of rock are exposed ______ (90°) to the sea, causing uneven rates of erosion.
On a discordant coastline, alternating bands of rock are exposed perpendicular (90°) to the sea, causing uneven rates of erosion.
What landforms does a discordant coastline produce?
Headlands (in more resistant rock) and bays (in less resistant rock).
True or False?
A concordant coastline produces headlands and bays.
False.
A concordant coastline produces coves (even erosion); headlands and bays form on a discordant coastline.
Define a wave-cut platform.
A wide, gently sloped surface found at the foot of a cliff, left behind as the cliff retreats.
How is a wave-cut notch formed?
The sea attacks the base of a cliff between the high and low water mark, forming a notch.
Which three erosion processes extend the wave-cut notch into a cliff?
Abrasion, corrosion and hydraulic action.
On a discordant coastline, why does a bay form in softer rock?
Softer rock (e.g. clay) is eroded backward to form an inlet that curves inwards into a bay, usually with a beach, while harder rock is left protruding.
The harder rock (e.g. limestone) is left protruding out to sea as a ______.
The harder rock (e.g. limestone) is left protruding out to sea as a headland.
Define wave refraction.
As waves slow along the sea floor they turn so the crest becomes parallel to the coast, concentrating erosive action on all sides of a headland.
Describe the sequence in which caves, arches, stacks and stumps form on a headland.
A crack widens into a cave; the cave breaks through the headland to form an arch; the arch roof collapses leaving a stack; the stack is undercut until it collapses into a stump.
What happens to an arch to form a stack?
The base of the arch becomes wider and thinner through erosion until the roof collapses, leaving an isolated column of rock (the stack).
A stack is ______ at its base by wave action until it collapses to form a stump.
A stack is undercut at its base by wave action until it collapses to form a stump.
True or False?
Attrition is one of the processes that forms caves, arches and stacks.
False.
Attrition is not part of this process; it is the knocking together of rocks to smooth and round them. The key processes are hydraulic action, abrasion and corrosion.
Why is corrosion a key process in forming coastal erosion landforms?
All salt water is slightly acidic and most rock contains soluble minerals that react with it.
How does rock type affect cliff profile?
Soft rock erodes quickly and forms sloping cliff faces; steep cliffs form where hard rock faces the sea.
What does continued undercutting of a wave-cut notch lead to?
Continued undercutting leaves the cliff above unsupported until it collapses.
Which type of wave builds a beach, and how do its swash and backwash compare?
A constructive wave, whose swash is stronger than the backwash, causing deposition.
Why is a beach sorted by size, with the largest material at the top?
The largest material is dropped at the top of the swash; as backwash loses energy through the porosity of the sand, deposited sediment gets progressively smaller, with the smallest mud settling offshore.
Define a berm.
A ridge of large shingle thrown above the usual high tide level at the top of a beach, formed by a destructive wave during a storm.
Define a spit.
An extended stretch of sand or shingle that extends out to sea from the shore, formed where the coastline changes shape or at a river mouth.
By which process is sediment transported to form a spit?
Sediment is transported by longshore drift.
Spurn Point, a spit stretching three and a half miles across the ______ Estuary, is found in the northeast of England.
Spurn Point, a spit stretching three and a half miles across the Humber Estuary, is found in the northeast of England.
What forms in the sheltered area behind a spit?
Silts are deposited to form salt marshes or mud flats.
Define bar (sandbar).
A landform that occurs when a spit grows across a bay, joining two headlands together; it can trap a lagoon behind it.
What is the difference between a bar and a barrier island?
A bar joins two headlands, whereas a barrier island is open at one or both ends and lies parallel to the coast.
Define a tombolo.
A depositional landform where a spit joins the mainland to an island; e.g. Chesil Beach joins the mainland to the Isle of Portland.
In sand dune formation, windblown sand is deposited against an ______ such as a pebble or driftwood, and the dunes grow as more sand is trapped.
In sand dune formation, windblown sand is deposited against an obstruction such as a pebble or driftwood, and the dunes grow as more sand is trapped.
Which grass stabilises fore dunes with its root system?
Marram grass stabilises the fore dunes.
True or False?
A lagoon is a permanent feature that lasts forever.
False.
A lagoon is a small body of water cut off from the sea (behind a bar or tombolo); it does not last forever and may fill with sediment to form new land.
What causes a spit's hooked end?
A change in wind direction alters the wave pattern to produce a hooked end.
What is the final, most stable stage of dune succession?
The mature dune, which can support flora such as oak trees.
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