Waves: The Driving Force of Coastal Change
- Coastlines are shaped by a dynamic interplay of natural processes.
- Understanding these processes is key to analyzing how coastlines evolve.
- Waves are the primary agents of coastal change, influencing both erosion and deposition.
- There are two major types of waves: destructive and constructive.
Waves Form When Wind Energy is Transferred to The Water's Surface.
- Wind blowing across the ocean creates friction, disturbing the water and transferring energy.
- This energy generates waves, which travel toward the shore, shaping the coastline through erosion and deposition.
- Wheres destructive waves carry higher energy causing erosion, constructive waves have lower energy resulting in deposition.
Destructive waves have a stronger backwash than swash, while constructive waves have a stronger swash than backwash.
Tides Are The Rhythmic Rise and Fall of the Sea
Tides
Tides are very long-period waves that move through the ocean in response to the gravitational forces exerted by the moon and sun.
Why Tides Matter
- Tidal Range
- A wide tidal range exposes more coastline to erosion and deposition.
- A narrow tidal range limits these processes to smaller areas.
- Sediment Transport
- Tides move sediment along the coast, contributing to the formation of features like mudflats and salt marshes.
Don’t confuse tides with waves! Tides are caused by gravitational forces, while waves are generated by wind.
Sediment Supply: The Building Blocks of Coastal Landforms
Sediment
Sediment is the raw material (small, solid particles consisting of various materials, including rock fragments, minerals, organic matter, and shells) transported and deposited by water, wind, ice, or gravity.
In case of coastal processes, sediment is mostly transported by water and wind and serves as building material for beaches, dunes, and other coastal landform.
Sources of Sediment
- Rivers: Transport fine-grained materials like silt and sand to the coast.
- Cliff Erosion: Provides larger materials like rocks and pebbles.
- Wind and Waves: Move sediment from offshore areas or nearby beaches.
The Nile River supplies sediment to the Nile Delta, creating fertile land and sandy beaches.
Why Sediment Matters
- Abundant Sediment: Promotes deposition, forming beaches and spits.
- Limited Sediment: Increases erosion, leading to coastal retreat.
Can you identify the main source of sediment for a beach near you? How might this source be affected by human activities?
Lithology: The Role of Rock Type and Structure
Lithology
Lithology refers to the composition and structure of rocks along the coastline, which influences erosion and landform development.
Key Factors
- Rock Type
- Hard Rocks: Granite and basalt resist erosion, forming cliffs and headlands.
- Soft Rocks: Limestone and sandstone erode quickly, creating bays and beaches.
- Rock Structure
