Coasts EQ2

Constructive waves

Low energy waves, and build up beaches by depositing sand and sediment. Result in a gentle slope. Longer wave period, greater swash than backwash. Low frequence, under 10 a minute.

Destructive waves

High energy waves with a short wavelength and a steep wave profile. Result in erosion of cliffs and shorelines and formation of features like wave-cut platforms and sea stacks. Greater backwash than swash. High frequency, 10-14 a minute.

How have beach sediment profiles changed over time?

Sediment supply from rivers is reduced due to dam construction. Interference in sediment supply along the coast due to building of groynes in coastal management. A warming climate in the UK will result in a winter beach profile being more common, with a lower water line.

What is fetch?

The distance a wave has travelled in open water before breaking. Impacts size of waves.

What does wave energy depend on?

Speed of wind, faster wind travelling, bigger wave will become. Time of wind, wave will become larger the longer wind acts upon it. Distance of wind, farther wind travels against the wave, bigger it will become.

What is spring tide?

Tides that occur twice a month when the Sun and Moon align on same side of Earth.

What is neap tide?

Tides that occur twice a month when the Sun and Moon are at right angles to Earth.

What is the difference between currents and tides?

Currents refer to the large scale movement of water across oceans via wind, creating waves. Tides are determined by the gavitational pull of the Sun and Moon, determining rise of sea levels.

Erosional landform cycle

Cracks opened by hydraulic action. Crack grows into a cave by hydraulic action and abrasion. The cave breaks through the headland to form an arch. The arch is eroded and collapses, leaving a tall roclk tack. Stack is eroded forming a stump.

What is a blowhole?

A vertical shaft in coastal rock formed by wave action, with water and air pressure create eruptions from the cave.

What are microfeatures?

Small-scale coastal features, including joints, wave-cut notches.

What is hydraulic action?

Water exerts pressure on cracks breaking them apart.

What is cavitation?

Opening of cavities in cliffs via pressure change exerted in hydraulic action.

What is wave quarrying?

Destructive waves in storms create heavy hydraulic action, causing shockwaves and vibrations that dislodge and undercut rock.

How does lithology influence hydraulic action?

Hydraulic action very effective on rocks with natural faults, sedimentary, and can weaken it, changing its structure.

What is abrasion?

Process of sediment wearing away rock surfaces as they hit cliffs in high-energy waves.

How does lithology influence abrasion?

Softer rock are less resistant and prone to abrasion, but over time, it is still able to affect harger rocks such as granite.

What is attrition?

The process of rocks and pebbles colliding and breaking down, reduction in size and smoothing of particles.

How does lithology influence attrition?

Downstream gravel becomes more rounded as transported, changing composition of sedimentary rock deposites later in cycles.

What is solution?

Dissolution of soluble rocks as a chemical weathering process. Often the calcium carbonate in limestone.

How does lithology influence solution?

Significant in carbonate rocks like limestone which dissolve over time can reduce rock volume and mineral composition.

What factors impact sediment transportation?

Currents Tides Longshore drift Angle of wave attack

What are currents?

Large scale movement of water across oceans via wind.

What are tides?

Periodic rise and fall of sea levels Caused by gravitational forces influenced by the Moon and Sun Two high tides and two low tides daily

How is sediment mainly moved?

Longshore drift, swash moves sediment at wave angle, backwash returns it downslope.

How do tides affect sediment transport?

Determine how much sediment moved and where. Large tidal ranges produce sediment to be transported over a large area.

What are the 4 forms of transportation?

Traction Saltation Suspension Solution

What is traction?

Large heavy sediment rolls along sea bed, pushed by currents.

What is saltation?

Smaller sediment bounces along sea bed, pushed by currents.

What is suspension?

Small sediment carried in the flow of water.

What is solution?

Dissolved material carried within the water.

Forms of depositional landforms

Spit Bayhead beach Tombolo Barrier beach/ bar Recurved spit Cuspate foreland

What is a spit?

Strip of land formed by LSD, waves lose energy and deposit seidment. Hook can form if wind changes direction. Example: Spurn Head

What is a bayhead beach?

Curved beach found at the back of a bay, formed by low wave energy and deposition. Example: Dungeness, Kent

What is a tombolo?

Bar or beach connecting mainland to offshore island. Formed by wave refraction allowing deposition. Example: Chesil Beach

What is a barrier beach/ bar?

A spit crossing a bay, linking the sections of the coast. Example: Loe Bar, Cornwall

What is a recurved spit?

Spit forming in estuary, river current prevents deposition across bay. Example: Spurn Head

What is a cuspate foreland?

Triangular shaped headland cause LSD along each side of headland to form beaches. When they meet, form cuspate foreland. Example: Dungeness, Kent.

What is the sediment cell?

Self-contained system acting as a source of sediment. 11 cells in England and Wales. Not entirely closed, some actions may affect other ones.

Dynamic equilibrium

Inputs and outputs changing yet they remain in balance.

Negative feedback

Lessens any change in a system.

Positive feedback

Exacerbates change, system becomes more unstable.

What is mechanical weathering?

Physical breakdown of rocks, no chemical change. Includes freeze-thaw, salt crystallisation, wetting and drying. Wetting and drying, rocks such as clay expand when wet and contract when drying, cycles can cause breaks.

What is chemical weathering?

Carbonation, rainwater absorbs CO2 to create weak carbonic acid, dissolves rock. Oxidation, minerals exposed to air via fissures, mineral increases volume as it is oxidised, rock begins to crumble. Solution, salt minerals in rock are dissolved.

What is biological weathering?

Plant roots can grow into cliff faces, weakening them. Birds nest in cliffs. Seaweed acids.

What is mass movement?

Downhill flow or slide of rock, soil and sediment on slopes. Driven by gravity.

Forms of mass movement?

Fall Topple Translational slide Rotational slumping

What is mass movement, fall?

Pieces of rock break of cliffs, often after freezing-thaw weathering. Mass falls occur when gravity causes rock fragments to tumble down steep slopes.

What is mass movement, topple?

Type of landslide where a block of rock rotates forward away from a slope at a pivot by the base. Occurs when the center of gravity shifts beyond the base of support.

What is mass movement, translational slide?

Movement of material along a planar surface, occurs on steep slopes. Often rapid, influenced by gravity and water saturation.

What is mass movement, rotational slumping?

Move along a curved spoon shaped surface, causes upper part to tilt backward. Slower and more contained.

Landforms created by mass movement

Rotational scars Scree clope Terraced cliff profile

What is a rotational scar?

Formed by rotational slumping Characterized by a steep cliff face Often features a crescent shape

What is a scree slope?

Accumulation of loose rock fragments Formed by weathering and mass movement Typically found at the base of cliffs

What is a terraced cliff profile?

A series of flat platforms or stepped ledges Formed by erosion and weathering Indicates varying resistance of rock layers