B.2.1 Physical Influences on Coastal Landscapes Notes

Waves: The Driving Force of Coastal Change

1. Coastlines are shaped by a dynamic interplay of natural processes.
2. Understanding these processes is key to analyzing how coastlines evolve.
3. Waves are the primary agents of coastal change, influencing both erosion and deposition.
4. There are two major types of waves: destructive and constructive.

Waves Form When Wind Energy is Transferred to The Water's Surface.

1. Wind blowing across the ocean creates friction, disturbing the water and transferring energy.
2. This energy generates waves, which travel toward the shore, shaping the coastline through erosion and deposition.
3. Wheres destructive waves carry higher energy causing erosion, constructive waves have lower energy resulting in deposition.

Tides Are The Rhythmic Rise and Fall of the Sea

Why Tides Matter

1. Tidal Range
   1. A wide tidal range exposes more coastline to erosion and deposition.
   2. A narrow tidal range limits these processes to smaller areas.
2. Sediment Transport
   1. Tides move sediment along the coast, contributing to the formation of features like mudflats and salt marshes.

Sediment Supply: The Building Blocks of Coastal Landforms

Sources of Sediment

1. Rivers: Transport fine-grained materials like silt and sand to the coast.
2. Cliff Erosion: Provides larger materials like rocks and pebbles.
3. Wind and Waves: Move sediment from offshore areas or nearby beaches.

Why Sediment Matters

1. Abundant Sediment: Promotes deposition, forming beaches and spits.
2. Limited Sediment: Increases erosion, leading to coastal retreat.

Lithology: The Role of Rock Type and Structure

Key Factors

1. Rock Type
   1. Hard Rocks: Granite and basalt resist erosion, forming cliffs and headlands.
   2. Soft Rocks: Limestone and sandstone erode quickly, creating bays and beaches.
2. Rock Structure
   1. Joints and Faults: Weaknesses in the rock that waves can exploit.
   2. Angle of Dip: Determines cliff stability and shape.

Vegetation: Nature’s Coastal Protector

1. Vegetation plays a critical role in stabilizing coastlines and reducing erosion.

How Vegetation Helps

1. Root Systems: Bind soil and sand, preventing erosion.
2. Windbreaks: Reduce wind speed, limiting sand movement.
3. Organic Matter: Enriches soil, promoting further plant growth.

Example

Vegetation plays important role in stabilizing sand dunes

• Pioneer Species: Plants like marram grass colonize dunes, stabilizing them with deep roots.
• Succession: Over time, more complex vegetation develops, anchoring the dunes further.

Subaerial Processes: Weathering and Mass Movements

1. Subaerial processes occur above the waterline and shape cliffs and slopes.

Key Processes

1. Weathering: Breaks down rocks through physical, chemical, or biological means.

1. Mass Movements: Gravity-driven movements like landslides or rockfalls.

Wave Processes: The Mechanics of Erosion and Transport

1. Waves are not just about energy, they are also about action.

Littoral Drift: The Coastal Conveyor Belt

1. Waves approach the shore at an angle, carrying sediment in the direction of the wind.
2. Swash moves sediment up the beach at an angle.
3. Backwash pulls sediment straight down due to gravity.
4. The process repeats, moving sediment along the coast.

Example

• Littoral drift is responsible for forming features like spits and barrier beaches.
• For example, the famous Spurn Head in England was created by sediment transported along the coast.

Hydraulic Action: The Power of Pressure

Hydraulic action occurs when waves crash against rocks, forcing air and water into cracks.

1. Pressure builds within the cracks as the wave hits.
2. Air expands and escapes when the wave retreats, causing the rock to weaken and break apart.

Abrasion: Nature’s Sandpaper

1. Abrasion occurs when sediment carried by waves scours rock surfaces, wearing them down over time.