Coastal Landscapes: Systems, Processes, and Landforms

Comprehensive review flashcards covering coastal sediment budgets, physical, chemical, and biological weathering, mass movement, marine, fluvial, and aeolian processes, and the formation of cliffs and shore platforms.

How do warm ocean currents influence coastal landscape systems?

They transfer heat energy from low latitudes toward the poles, particularly affecting western-facing coastal areas driven by onshore winds, directly affecting air temperature and sub-aerial processes.

What proportion of coastal sediment can rivers contribute in certain coastal locations?

In some locations, as much as $90\%$ of coastal sediment comes from rivers.

Under what conditions can cliff erosion contribute up to $70\%$ of the material supplied to beaches?

During the erosion of weak cliffs in high-energy wave environments.

How is beach nourishment carried out to manage a coastal sediment budget in deficit?

Sediment can be brought in by lorry and spread by bulldozers, or sand and water can be pumped onshore by pipeline from offshore sources with low bunds holding the mixture while water drains away.

Based on the sediment budget data for Nigeria in Table 1.2, what are the total inputs and outputs, and is the budget in surplus or deficit?

Inputs total $4896\,\text{m}^3/\text{year}$ ($1187 + 251 + 3458$) and outputs total $5510\,\text{m}^3/\text{year}$ ($2641 + 2869$), placing the budget in a deficit state.

What are the three primary sediment stores identified in the coastal sediment budget system?

Dunes, beaches, and sandbanks.

Why are some mechanical weathering processes rendered ineffective in coastal landscapes such as western Europe?

The presence of the sea moderates air temperatures so they seldom drop below $0^\circ\text{C}$, reducing temperature fluctuations.

By what percentage does water expand when it freezes within rock cracks during freeze-thaw weathering?

It expands by nearly $10\%$.

What is dilatation (pressure release), and what rock feature does it produce?

When overlying rocks are removed by weathering and erosion, the underlying rock expands and fractures parallel to the surface, forming fractures called pseudo-bedding planes.

Which salt compounds are particularly effective in salt crystallisation, and by how much do they expand at temperatures around $26\text{--}28^\circ\text{C}$?

Sodium sulphate and sodium carbonate, which expand by about $300\%$.

What does Van't-Hoff's Law state regarding chemical weathering rates and temperature?

A $10^\circ\text{C}$ increase in temperature leads to a $2.5$ times increase in the rate of chemical reaction (up to $600^\circ\text{C}$).

Why can carbonation weathering be more effective in low-temperature coastal environments?

Because carbon dioxide is more soluble in cold water than in warm water.

What product is formed when feldspar in granite undergoes the chemical weathering process of hydrolysis?

Feldspar reacts with hydrogen in water to produce kaolin (china clay).

What structural and volumetric changes occur during the chemical weathering process of hydration?

Water molecules added to rock minerals create new minerals of a larger volume (such as anhydrite taking up water to form gypsum), expanding minerals by about $0.5\%$ and causing surface flaking.

How do blue-green algae and molluscs contribute to biological weathering in coastal environments?

Blue-green algae produce a shiny film of iron and manganese oxides on rocks, while molluscs on shore platforms secrete acids that produce small surface hollows in rock.

Under what cliff slope conditions does rock fall typically occur?

On bare cliff faces with a slope angle of $40^\circ$ or more, where physical weathering detaches rocks that fall under gravity to form a scree slope.

Why does a layer of sand overlying clay encourage rotational slides (slumps)?

Rainwater penetrates the permeable sand but cannot penetrate the impermeable clay below, increasing pore pressure in the sands, while wet clay adds downslope weight.

What is the average pressure exerted by breaking Atlantic waves through hydraulic action?

An average pressure of $11{,}000\,\text{kg/m}^3$.

How much force can high-energy breaking waves exert through pounding?

Forces of as much as $30\,\text{tonnes/m}^2$.

How does the process of longshore drift transport and alter beach sediment?

Swash moves particles diagonally up the beach following dominant wind direction, and backwash pulls them perpendicularly down under gravity, moving material alongshore while attrition makes particles smaller and more rounded.

What pattern does sediment deposition follow as the velocity of moving water decreases?

Deposition is sequential: the largest and heaviest particles requiring the most energy deposit first, followed sequentially by progressively finer particles.

What causes the flocculation of clay particles when river water meets the sea?

Saline conditions generate electrical charges between fine, light clay particles, causing them to clump together, become heavier, and sink to the sea bed.

How does wind erosive capacity change when wind velocity increases from $2\,\text{m/s}$ to $4\,\text{m/s}$?

It causes an eight-fold increase in erosive capacity, because erosive force increases exponentially with wind velocity.

Why is wind abrasion on rocky coastlines and cliffs largely restricted to a height of about $1\,\text{m}$?

Sand grains are relatively heavy compared to silt and clay, so wind at $40\,\text{km/h}$ moves them via surface rolling and saltation rather than carrying them in suspension.

What specific grain sizes are transported by suspension, saltation, and surface creep in aeolian processes?

Suspension carries grains of $0.05\text{--}0.14\,\text{mm}$, saltation carries grains of $0.15\text{--}0.25\,\text{mm}$, and surface creep moves grains of $0.26\text{--}2\,\text{mm}$.

How does seaward-dipping rock strata affect cliff profiles and collapse patterns?

Undercutting removes basal support, causing loosened rock layers to slide into the sea along bedding planes, producing a cliff profile that follows the angle of the dipping strata.

What maximum width does a shore platform typically reach before wave undercutting of the cliff ceases?

A maximum width of about $500\,\text{m}$.

Why do shore platforms typically feature a ramp at high tide level and a small cliff at low tide level?

Water levels remain constant for the longest duration at high and low tide, concentrating wave erosion at those points.

How does a tidal range greater than $4\,\text{m}$ alter the development of a shore platform?

Erosion is spread over a wider area because water remains at high and low tide positions for shorter periods, making the platform more uniform and more steeply sloping.

Why do marine algae accelerate chemical weathering on exposed shore platforms at night?

Photosynthesis ceases at night and algae release $\text{CO}_2$, which mixes with sea water to make it more acidic, accelerating chemical weathering.