Key Terms: Coastal Systems & Processes (AQA A Level Geography): Revision Note

Coastal systems - key terms

Constructive wave – A type of wave with strong swash and weak backwash that deposits material, building up beaches with a gentle profile.

Destructive wave – A wave with strong backwash and weak swash that erodes beaches and creates a steep profile.

Dynamic equilibrium – A state of balance within a coastal system, where inputs and outputs of sediment are equal over time.

Fetch – The distance over which the wind blows uninterrupted across the sea surface; affects wave energy.

High energy coastline – A coastline exposed to strong waves and wind where erosion exceeds deposition, forming cliffs, arches, and wave-cut platforms.

Low energy coastline – A sheltered coastline where wave energy is low and deposition exceeds erosion, forming beaches and spits.

Rip current – A narrow, fast-moving flow of water returning seaward through breaking waves; a localised high-energy current.

Sediment budget – The balance between the inputs, outputs, stores, and transfers of sediment within a coastal system.

Sediment cell – A stretch of coastline where sediment movement is largely self-contained; helps manage coastal processes more effectively.

Tidal range – The vertical difference between high and low tide; influences the level of wave action on the coastline.

Wave refraction – The bending of waves as they approach the coast, concentrating energy on headlands and reducing it in bays.

Sub-aerial processes - key terms

Biological weathering – Breakdown of rock due to living organisms such as plant roots, burrowing animals, or humans.

Chemical weathering – The decomposition of rocks by chemical processes including:

• Carbonation – Rainwater (slightly acidic) reacts with carbonate rocks (e.g., limestone).

• Oxidation – Reaction of iron-rich rocks with oxygen, leading to rust and weakening.

• Solution – Dissolving of minerals in rock by water.

Exfoliation (onion skin weathering) – A type of physical weathering in hot climates where rocks expand during the day and contract at night, causing layers to peel off.

Mass movement – The downslope movement of rock and soil under gravity, includes:

• Creep – Slow movement of soil down gentle slopes.

• Flow – Movement of saturated soil down moderate slopes.

• Slide – Rapid movement of material along a plane.

• Slump – Rotational movement of saturated material on a curved surface.

• Fall – Sudden dropping of rock fragments from steep slopes.

Salt crystallisation – A weathering process where salt crystals expand in rock pores, exerting pressure and causing the rock to break apart.

Wetting and drying – Physical weathering process where rock expands when wet and contracts when dry, causing cracks to form.

Marine processes - key terms

Abrasion (corrasion) – The scraping of rock surfaces by materials carried in waves, causing erosion.

Attrition – The breaking down of sediment as particles collide and become smaller and rounder.

Hydraulic action – The force of water hitting rock, forcing air into cracks and weakening the rock structure.

Longshore drift – A zigzag movement of sediment along the coast caused by waves approaching at an angle due to prevailing wind direction.

Marine deposition – The laying down of material by waves when they lose energy, forming features like beaches and bars.

Marine erosion – The wearing away of the coast by wave action, especially by destructive waves.

Marine transportation – The movement of sediment by sea in four main ways:

• Traction – Rolling of large sediment along the seabed.

• Saltation – Bouncing of small particles.

• Suspension – Fine material carried within the water.

• Solution – Dissolved materials transported in seawater.