IGCSE Geography: 2.3 Coasts

Introduction to Coastal Processes

Overview of the Holderness Coastline

• The video introduces the topic of coastal geography, focusing on the Holderness coastline as a case study for understanding opportunities presented by coastal areas.

• It highlights marine processes that are similar to river processes discussed in previous content.

Marine Erosion Processes

• Marine erosion includes four key processes: abrasion, attrition, hydraulic action, and solution (corrosion).

• Abrasion: Rocks grind along the sea bank or bed, wearing it away.

• Attrition: Rocks collide with each other, resulting in smaller fragments.

• Hydraulic Action: Water pressure increases in cracks of cliffs leading to explosive erosion.

• Solution (Corrosion): Chemical reactions between seawater and minerals dissolve materials.

Marine Transport Mechanisms

Types of Marine Transport

• Five types of marine transport are identified:

• Suspension: Small loads held up by water flow.

• Saltation: Heavier loads bounced along the seabed.

• Solution: Chemical load dissolved in water.

• Traction: Heaviest loads dragged along the seabed.

• Flotation: Very light materials like leaves carried on water's surface.

Wave Dynamics

Key Wave Terminology

• Important terms related to wave action include:

• Swash: Movement of material up the beach towards land due to wind direction.

• Backwash: Movement of water back down into the ocean due to gravity.

Types of Waves

• Two main types of waves are described:

• Constructive Waves: Long wavelength and low height; they build beaches through deposition.

• Destructive Waves: High height and short wavelength; they erode beach materials and cliffs.

Impact of Wind on Coastal Processes

Influence on Wave Formation

• Wind affects wave energy; prevailing winds can increase wave amplitude significantly.

• Longshore drift is introduced as a process where material moves along a beach due to wave action.

Longshore Drift Explained

• Longshore drift involves waves moving material up (swash) and back down (backwash), generally transporting sediment in one direction along the coast.

• This process can lead to significant beach erosion as materials are unevenly distributed across beaches.

Coastal Erosion and Deposition Features

Coastal Erosion Features

• Erosion Process: Coastal erosion leads to various geological features such as caves, arches, stacks, stumps, cliffs, wave-cut platforms, headlands, and bays. These will be explored in detail later.

• Formation of Caves and Arches: Initially, hydraulic action creates a cave from a crack in the rock. Continuous erosion transforms this cave into an arch as water erodes inward. Eventually, the arch collapses due to gravity when it can no longer support itself.

• Stacks and Stumps: After the collapse of an arch, a stack is formed which is subsequently weakened by wave action at its base until it collapses into a stump. This illustrates the sequential nature of coastal erosion features.

• Cliffs and Wave-Cut Platforms: Cliffs are formed through hydraulic action and abrasion at their bases leading to notches that cause collapses over time. The area below becomes a wave-cut platform as material is eroded away. This process resembles how waterfalls are formed.

• Headlands and Bays Formation: Alternating layers of resistant (hard) and less resistant (soft) rocks lead to headlands forming where hard rocks remain while softer rocks erode faster creating bays. This results in distinct coastal formations visible from both top-down and side views.

Coastal Deposition Features

• Beaches Definition: Beaches are accumulations of materials deposited between high spring tides and regular tides; they can also form storm beaches where materials are pushed up by strong waves during storms.

• Bars and Spits Explained: A bar is a shallow sandbank found at river mouths or estuaries created by longshore drift processes that transport sediment along the beach; spits extend from land into water where wave energy decreases allowing deposition to occur.

• Spit Formation Dynamics: As spits develop due to longshore drift, they may curve due to wind direction changes; this process can eventually isolate areas creating lagoons behind them when bays become cut off by bars forming new landforms over time.

• Sand Dunes Characteristics: Coastal sand dunes form through strong onshore winds transporting sand inland; these dunes can threaten nearby settlements if not managed properly due to their mobility across landscapes influenced by wind patterns. Different types include embryo dunes, yellow dunes, gray dunes among others based on their development stages influenced by environmental factors like vegetation growth or human activity.

This structured overview captures key concepts related to coastal erosion and deposition features discussed in the transcript while providing timestamps for easy reference back to specific sections of the content.

Coral Reefs and Mangroves: Ecosystems Under Threat

Understanding Coral Reefs

• Coral reefs are underwater ecosystems formed by reef-building corals, which create calcium carbonate structures. They thrive in temperatures between 22°C to 25°C but can only survive in waters above 18°C and below 27°C.

• Global warming poses a significant threat to coral reefs; rising sea temperatures can lead to coral death. Corals require shallow, clean water with high salinity for optimal growth.

• The fishing industry contributes to coral destruction through harmful practices like dynamite fishing, alongside pollution from oil spills.

Types of Coral Reefs

• There are three main types of coral reefs: fringing reefs, barrier reefs, and atolls.

Importance of Mangroves

• Mangroves are salt-tolerant forests found in tropical coastal areas. They have adapted aerial roots that provide stability against wave action.

• Approximately 42% of the world's mangroves are located in Asia, primarily in tropical or subtropical regions.

• Mangroves play a crucial role in protecting coastlines by absorbing storm energy and providing resources such as food and building materials.

Coastal Management Strategies

• Coastal management involves two primary approaches: soft engineering (working with nature) and hard engineering (building protective structures).

• Soft engineering methods include beach nourishment and offshore reefs, while hard engineering includes seawalls and rock armor designed to protect coastal areas.

Case Study: Holderness Coastline

• The Holderness coastline on England's east coast is experiencing rapid erosion at an average rate of 2 meters per year, significantly higher than the UK average of 0.43 meters per year.

• Opportunities near the Holderness coastline include tourism-related activities that contribute to the local economy; however, only 4.5% of the local population is employed in agriculture.

Erosion Factors at Holderness Coastline

• The geology of the Holderness coast consists mainly of less resistant boulder clay, making it more susceptible to erosion due to strong prevailing winds from the northeast.

• These winds create longshore drift that transports materials along the coast, leading to loss of property and recreational areas as sediment is moved southward.

Coastal Erosion and Management Techniques

Understanding Coastal Erosion

• The discussion begins with an illustration of wind direction affecting coastal erosion, emphasizing that prevailing winds can lead to significant land erosion near structures like houses.

• As the coastline erodes, valuable personal property is at risk, highlighting the importance of effective management strategies for coastal areas.

Engineering Solutions for Coastal Protection

• Hard engineering methods such as groins and rock groins are introduced. These structures trap sediment from longshore drift to maintain beach integrity.

• A specific example is provided where rock groins were constructed in Holderness Coast after a community campaign, costing around £2 million to protect against erosion.

Soft Engineering Approaches

• Beach nourishment or replenishment is discussed as a soft engineering method aimed at adding sediment to eroded beaches, particularly in northern coastal areas.

• The process involves redistributing sand to balance beach levels but poses risks during storms due to the temporary nature of added materials.

Challenges and Considerations

• The vulnerability of newly nourished beaches during severe weather events is emphasized, indicating that while these methods can be beneficial, they require careful consideration regarding their sustainability and effectiveness.

This concludes the overview of coastal erosion management techniques discussed in the video.