Crowded Coasts 2.3.2 Flashcards
Enquiry Question: How do physical processes produce coastal landforms and landscapes?
What are the key characteristics of constructive waves?
Low height, long wavelength, strong swash, weak backwash, low frequency (6–9/min), deposit sediment
What are the key characteristics of destructive waves?
High height, short wavelength, weak swash, strong backwash, high frequency (11–16/min), erode beaches.
How does wave frequency influence coastal processes?
Higher frequency waves (destructive) increase erosion; lower frequency waves (constructive) build beaches.
What type of wave is more common in summer, and how does it shape the beach?
Constructive waves dominate, leading to wider, gently sloped beaches.
How do destructive waves alter the beach profile in winter?
Remove sediment, creating narrower, steeper beach profiles.
Define swash and backwash.
Swash: movement of water up the beach. Backwash: movement of water returning to the sea.
What is the difference between a swash-aligned and a drift-aligned coast?
Swash-aligned: waves hit parallel, little longshore drift. Drift-aligned: waves hit at an angle, causing longshore drift.
How does the angle of wave approach influence sediment transport along the coast?
The steeper the angle, the more effective longshore drift is at transporting sediment.
What kind of beach forms under low-energy wave conditions?
Sandy, gently sloping beaches due to deposition.
How do seasonal changes influence beach sediment profiles?
Summer: deposition dominates (wider beach). Winter: erosion dominates (narrower beach).
Name the six main marine erosion processes.
Hydraulic action, abrasion, attrition, corrosion (solution), corrasion, wave quarrying
What is hydraulic action and how does it affect rock structures?
Waves force air into cracks, increasing pressure and causing rock to fracture.
Describe abrasion and how it contributes to cliff erosion.
Sediment in waves grinds against the cliff face, wearing it down.
How does attrition differ from corrasion?
Attrition is rocks hitting each other and breaking down; corrasion is rocks hurled at cliffs by waves.
Which rock type erodes the fastest: granite, limestone, or basalt?
Limestone (sedimentary)
Why are sedimentary rocks more prone to erosion?
They are clastic with many faults and joints, making them weaker.
What erosion rate would you expect for metamorphic rocks?
0.1–0.3 cm/year — slower due to crystalline structure.
How do cracks and faults influence the erosion of a cliff face?
They allow water and pressure to enter, accelerating erosion processes like hydraulic action.
What is a composite cliff and how is it formed?
A cliff made of multiple rock types with different resistances, creating a layered profile.
How does the dip of rock strata influence cliff stability?
Seaward dip: unstable cliff; landward dip: more stable. Horizontal dip forms steep cliffs.
Explain the formation of a wave-cut notch.
Erosion at the cliff base creates a notch between high and low tide.
What is a wave-cut platform and how is it created?
As the notch deepens, the cliff collapses, leaving a flat platform.
Describe the sequence of landforms formed from cave to stump.
Fault → cave → arch → stack → stump.
What physical and marine processes contribute to the formation of blowholes?
Marine erosion forms a cave; weathering creates a pothole above. When they meet, a blowhole forms.
How do headlands and bays form on a discordant coastline?
Softer rock erodes into bays, while resistant rock forms headlands.
What role does wave refraction play in coastal landform development?
Concentrates energy on headlands (erosion) and disperses it in bays (deposition).
How does differential erosion create complex cliff profiles?
Different layers erode at different rates, forming overhangs, notches, and varied slopes.
Why do some headlands erode faster than others?
Headlands with more joints, faults, or weaker rock erode more rapidly.
What are the three types of weathering affecting coasts?
Mechanical (physical), chemical, biological.
Describe freeze-thaw weathering and its impact on cliff faces.
Water enters cracks, freezes, expands, and forces rock apart.
What is salt crystallisation and how does it contribute to rock weakening?
Salt left after seawater evaporates forms crystals that widen cracks.
How do plant roots contribute to biological weathering?
Roots grow into cracks and exert pressure, splitting the rock.
What is the difference between a slide and a flow in mass movement?
Slide: material moves as a block. Flow: material mixes and moves more fluidly.
What conditions favour the occurrence of slumping?
Saturated soft rock (e.g. clay), gentle dip, and lack of vegetation.
Define solifluction and where it commonly occurs.
In tundra areas; thawed top layers flow over frozen ground in summer.
How does rainfall influence sub-aerial processes?
Increases saturation, leading to slumping and enhances weathering.
Describe how longshore drift works.
Waves hit the beach at an angle, swash moves sediment up, backwash pulls it straight down, creating zig-zag motion.
What is the difference between traction and saltation?
Traction: large particles roll on the seabed. Saltation: smaller particles bounce along.
What conditions cause a wave to deposit its sediment?
Low energy conditions (e.g. shallow water, reduced wind), sediment becomes too heavy to carry.
How does flocculation influence deposition in coastal areas?
Clay particles clump together due to chemical attraction and sink.
Describe how a spit forms and how it develops a recurved end.
Longshore drift moves sediment into open water; wind direction changes, curving the end.
What is a tombolo, and how is it formed?
A depositional bar connecting mainland to an island, formed by wave refraction and sediment deposition.
Explain the difference between bars and cuspate forelands.
Bars join two headlands across a bay; cuspate forelands form between two converging longshore drifts.
Why are depositional landforms considered unstable?
Made of unconsolidated sediment, easily eroded or reshaped by storms or sea-level change
What is a sediment cell and why is it considered a closed system in theory?
A sediment cell is a stretch of coastline where the movement of sediment (inputs, transfers, and outputs) is largely self-contained. It is considered a closed system in theory because sediment doesn’t usually enter or leave the cell. This helps in managing the coast holistically, though in reality, some leakage can occur.
