Weathering, Erosion, and Mass Movement

• Weathering breaks down rocks near the Earth's surface into smaller pieces or ions, remaining in place.
• This is caused by chemical reactions, physical forces, or biological activity.
• Mass movement refers to the downward and outward movement of slope-forming materials due to gravity
• Examples include landslides, rockfalls, and slumps.
• Soil erosion by wind and rain removes topsoil from the land, leading to landscape changes.
• These are caused by wind and water.
• Hydraulic action occurs when the force of water breaks against rocks which compresses air in cracks, causing erosion.
• Wave quarrying involves breaking waves trapping air, exerting pressure, and causing rock chunks to break off cliffs.
• Abrasion (corrasion) involves material carried by waves grinding down rock surfaces.
• Attrition is where rocks carried by seawater smash together, breaking into smaller, smoother pieces.
• Solution (corrosion) involves dissolving soluble materials in rocks, such as limestone.
• Traction occurs when large boulders and rocks are rolled along the seabed by the force of the water.
• Suspension involves smaller particles being carried within the water column.
• Saltation is when small pebbles and stones are bounced along the seabed.
• Wave pounding is the sheer force of waves breaking against the shore or cliffs.

Coastal Open System

• Dynamic systems shape coastal landscapes.
• Components include inputs, components, stores, flows/transfers, and outputs.

Coastal Open System Components

• Inputs are external factors affecting the system, like wave energy and sediment supply.
• Components are elements within the system, like landforms and ecosystems.
• Stores (reservoirs) are locations storing materials or energy temporarily.
• Flows/transfers are movements of materials or energy within the system.
• Outputs are results or outcomes of processes within the system, like erosion and deposition.

Dynamic Equilibrium in Coastal Systems

• In dynamic equilibrium, the stores stay the same.
• If one element of the system changes, the stores change, upsetting the equilibrium.

System Change Example

• If there's an increase in inputs (like sediment supply), without changes in outputs (sediment transported out), the stores (sediment deposits, erosion rates) may change.
• This disrupts the system's equilibrium.
• Feedback describes phenomenon where changes in one system element lead to adjustments in others, disrupting equilibrium.

Positive Feedback

• The effects of an action amplify or are multiplied by a secondary effect.

Negative Feedback

• The effects of an action are nullified by its subsequent effects.
• Barrier islands protecting coastlines from erosion by absorbing wave energy is an example.
• As they grow, they provide more protection, further reducing erosion.

Feedback Exam Question Example Response

• The stores change and the equilibrium is upset if one of the elements of a dynamic equilibrium system changes.
• If one of the inputs increases without any corresponding change in the outputs, this is the the called feedback.
• Add example of negative feedback.

Negative Feedback Example - Storm Forming Bar, Offshore Bar Less Erosion, Restored

• Disruption- Increased wave energy erodes sediment from the beach, deposits it offshore, forming an offshore bar during storm.
• Response- Offshore bar causes incoming waves to break earlier, reducing energy before reaching the beach.
• Restoration- Less energy = less beach erosion; sediment from offshore bar gradually moves back to beach when storm calms, which helps restore state.

Positive Feedback Example: Sea Levels Rise Causing Continuous Erosion

• Disruption- Sea levels rise due to climate change, increased water levels can lead to higher coastal erosion rates.
• Response- Erosion intensifies, more sediment is removed from the coastline.
• Exacerbation - Leads to protective feature loss (sand dunes); coast becomes more vulnerable to erosion.
• Result - Cycle where coastline increasingly erodes and becomes progressively unstable.

Factors that Influence Coastal Form & Nature

• Causes vs Factors - Explanation is a higher level skill than description

Negative Feedback Example Response

• Disruption- Increased wave energy erodes sediment from the beach, deposits it offshore, forming an offshore bar during storm.
• Response- Offshore bar causes incoming waves to break earlier, reducing energy before reaching the beach.
• Restoration- Less energy = less beach erosion; sediment from offshore bar gradually moves back to beach when storm calms, which restore state.

GPT Feedback Concepts Response

• Positive feedback: When a a system change leads to amplifying disruptions which leads to greater instability.
• Negative feedback: When a system change triggers processes that counteract initial disruptions which helps restore stability.
• Example of Positive Feedback: Rising sea levels increase coastal erosion. This erosion removes protective sand dunes, exposing the coast, leading to further instability.
• Example of Negative Feedback: A storm erodes sand from a beach, deposits it offshore, and forms a bar. The offshore bar causes waves to break earlier, reducing their energy and protecting the beach, which helps to stabilize the coastline.

Coastal System Concepts

• Dynamism- degree of change taking place within a scale and/or rate system.
• Negative feedback cycles are more common than positive feedback cycles.

Marine Inputs that Change Coastline

• Wind
• Waves
• Tides
• Currents.

Factors Affecting the Size of a Wave

• Wind velocity, duration of wind, and length of the fetch.

Wave Creation

• Waves created by transfer of energy from wind blowing over sea surface.

Factors Influencing Wave Energy

• Wind velocity, duration of wind, and length of the fetch.

Fetch Definition

• Maximum distance of open water wind can blow, with places having greatest fetch experiencing highest energy waves.

How Wind Velocity Affects Wave Energy

• Strength of wind (wind velocity) increases frictional drag, which increases size and energy of waves.

Effect of High Wind Speeds on Wave Energy

• Leads to higher wave energy

Prevailing Wind Direction Influence

• Affects coastal processes by influencing sediment transport.

Longer Wind Duration Affect on Wave Energy

• Increases wave energy.

How Wind Acts as Erosion Agent

• Picks up and removes sediment from the coast, causing abrasion.
• The main marine inputs that change the coastal system are wind, waves, tides, and currents.
• Factors affecting the size of a wave include wind velocity, period of time wind has blown, and length of the fetch.
• Fetch refers to the maximum distance of open water over which wind.
• As wind speed increases, the energy of the waves also increases.
• Breaker Waves - Waves break due to seabed friction slows its base which causes it to steepen and break.
• Waves are classified as

Destructive Wave Characteristics

• High, steep, with a short wavelength, and high frequency

Constructive wave Characteristics

• Low, with a long wavelength, and low frequency.
• High energy waves typically have headlands, cliffs, and wave-cut platforms.
• Low energy waves typically have beaches and spits

Baltic Example

• The Baltic Sea exemplifies a low energy wave coastline due to its short fetch

North Cornish Example

• The North Cornish coastline exemplifies a high energy wave coastline due to its exposure to strong prevailing winds which results in higher erosion rates.

Backshore

• The backshore is the area above the high water mark, only affected by waves during storms.

Foreshore

• The foreshore is the area between the high water mark (HWM) and low water mark (LWM).
• It is the most active zone for marine processes, such as erosion, deposition, and transportation, due to regular wave action and tidal changes.

Inshore

• The inshore extends from the low water mark (LWM) to the area where waves begin to break.

Offshore

• The offshore is the area beyond the point where waves cease to impact the seabed.
• Primarily characterized by sediment deposition.

Nearshore / Backshore

• Nearshore / Backshore extends from the low water mark to the area where waves begin to break.
• Includes swash zone is were Water washes up the beach after a wave breaks.
• Surf zone area is between wave breaks and swash moves up the beach.
• Breaker zone is were waves Start to break (usually in 5-10m deep water)

Fetch Defined

• The distance of open water over which wind blows uninterrupted which determines the magnitude (size) and energy of the waves reaching the coast

Erosion Defined

• The wearing away of the Earth's surface by the mechanical action of glaciers, wind, rivers, marine waves, and wind

Weathering Defined

• The breakdown of rock at or near the Earth's surface creates regolith that remains in situ until moved by later erosional processes.

Weathering

• Can be mechanical, biological/organic, or chemical

Wind's Role in Coastal Systems

• Energy Source: Wind creates waves and powers coastal processes like erosion and sediment movement.
• Fetch: The distance over water that wind blows without interruption which affects the size of the waves
• Wave Formation: Wind transfers energy to create waves and size depends on strength, duration, and fetch.
• Erosion and Transport: Wind erodes coastline by moving sediment, which can wear down other features. Transports sediment along coast and inland.

Wave Characteristics

• Wave Height or Amplitude: The height difference between a wave crest and the neighboring trough.
• Wavelength: The distance between successive wave crests.
• Wave Period: The time for one wave to travel the distance of one wavelength.

Wave Breaking Steps

• Approach Shallow Water: Waves move into shallower water and interact with seabed.
• Increase Friction: Friction between wave and seabed increases.
• Wave Slows Down: Base of wave slows due to friction.
• Height and Steepness Increase: As the base slows, the wave increases in height and becomes steeper.
• Wave Breaks: The top part of the wave becomes unstable and plunges forward, causing the wave to break on the shore.

Wave Swash and Backwash

• Rush of water up the beach is swash and water runs back down the beach towards the sea is backwash
• Constructive Waves: Low wave height, long wavelength, low frequency (6-8 waves per minute), stronger swash than backwash, build up beach material.
• Destructive Waves: High wave height, steep form, high frequency (10-14 waves per minute), stronger backwash than swash, remove more sediment than they add

Wave Refraction

• When waves approach a coastline that is not a regular shape, and wave energy becomes concentrated on the headland, causing greater erosion.

Holderness Coastline

• Located on east coast of England, it extends 61 km from Flamborough in the north to Spurn Point in the south.
• One of Europe's fastest eroding coastline at average annual rate of around 2 metres which is made up of soft, boulder clays (tills) that were left after the Devensian ice sheets retreat about 12,000 years ago.

Holderness Erosion Factors

• Geology: weak that contains 50 miles of boulderclay
• Wave power: waves fetch is short at {{cl::500km}} but  (or Swell) move northwards around the UK from the Atlantic and into the North Sea. The Atlantic's fetch is {{cl::5000km}}  Current add even more energy to the waves.
• Longshore drift Holderness material does not stay to protect the coast

Flamborough

• The chalk of Flamborough is a resistant rock that provides examples of erosion like caves and arches. The chalk has formed a headland. Spurn Head sand and shingle spit  {{cl::5.5}} km long, is reaching across the mouth of the Good example of Longshore drift.

Mappleton Management

• It has has been subject to intense erosion at {{cl::2.0}}m per year to support approximately{{cl::50}} properties and support {{cl::B1242}} main road so they constructed rock groynes and revetment .This inturn increased the erosion rate to the south in Aldbrough.

Wingbury Farm near Aldbrough

• Buildings have to be taken down and a Piggery, that was built 1973, had to be dismantled due to increased erosion rate

Holderness Slumping

• Soft boulder clay cliffs at Hornsea become saturated with rainwater, losing their strength, Cliff slumps reduces the cliff angle, temporarily preventing further erosion and large waves then remove the debris through longshore drift to the south.

Withernsea

• Management: The Withernsea settlement that attracts tourists, is using Sea Wall, Groynes and Beach Nourishment to defend against this problem.

Hornsea

• Hornsea lies upon boulder clay thats made of 72% mud and 27% sand with 1% boulders and large pebbles. It is being managed because its high population density of 8,327 with wide range of infrastructure that is in place. Using Sea Wall, Groynes and beach Nourishment for town defense.