The coastal system is shaped by four primary processes: erosion, weathering, transportation, and deposition. These processes continuously interact, altering the landscape and influencing the shoreline.
Coastal Processes Explained
Here's a detailed breakdown of each process:
1. Erosion
Erosion is the process where natural forces break down and remove earth materials. In the coastal context, this primarily involves the action of waves, tides, and currents.
- Wave Erosion: Waves pounding against cliffs can cause significant erosion.
- Hydraulic Action: The sheer force of water entering cracks and crevices in rocks can weaken and break them apart.
- Abrasion: Waves carry sand, pebbles, and rocks, which act like sandpaper, grinding away at the coastline.
- Corrosion (Solution): Seawater can dissolve certain types of rocks, such as limestone, over time.
2. Weathering
Weathering is the breakdown of rocks and minerals by physical, chemical, or biological processes. It works to weaken rock so that erosion can occur more easily.
- Physical Weathering:
- Freeze-Thaw: Water freezes in cracks, expands, and breaks rocks.
- Salt Crystallization: Salt crystals grow in rock pores, exerting pressure and causing disintegration.
- Chemical Weathering:
- Oxidation: Rock minerals react with oxygen causing them to break down, this is very common for iron-rich minerals.
- Hydrolysis: Minerals in rock react with water, causing their structure to change and weaken.
- Biological Weathering:
- Plant Roots: Tree and plant roots can grow into cracks, widening them, causing the rock to break apart.
- Organisms: Animals, bacteria, and lichens may also contribute to the breakdown of rocks.
3. Transportation
Transportation is the movement of eroded materials. The main agents of transport along coastlines include:
- Waves: Waves move eroded material both onshore and along the coast.
- Currents: Coastal currents move sediment along the shoreline.
- Tides: Tidal movements carry material in and out of the coastal zone.
- Longshore Drift: This is a special type of transportation where waves approach the shore at an angle, transporting material along the beach.
4. Deposition
Deposition occurs when the transported material is laid down or accumulates. This happens where energy levels drop, for example, in calmer waters.
- Beaches: Sand and pebbles deposited by waves create beaches.
- Sand Dunes: Wind transports and deposits sand, forming sand dunes.
- Spits and Bars: These elongated features form when deposition is influenced by changes in coastal direction.
- Estuaries: These are areas where rivers meet the sea, often with sediment deposits.
Summary Table
| Process | Description | Key Actions |
|---|---|---|
| Erosion | Breaking down and removal of earth material. | Hydraulic action, abrasion, corrosion. |
| Weathering | Breakdown of rocks and minerals in situ (on site). | Freeze-thaw, salt crystallization, oxidation, hydrolysis, plant roots. |
| Transportation | Movement of eroded material. | Waves, currents, tides, longshore drift. |
| Deposition | Laying down of transported material. | Formation of beaches, dunes, spits, bars, and sediments in estuaries. |
These four processes work in an interconnected manner, constantly reshaping and defining our coastlines.
