Waves carry sediments by using the energy of the water motion to erode, transport, and deposit materials like sand, silt, and gravel.
Here's a breakdown of how waves accomplish this:
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Erosion: Waves crashing against coastlines have significant erosive power. The force of the water, especially during storms, can break down rocks and dislodge sediment.
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Transport: Once sediment is eroded or already present (e.g., from rivers), waves transport it in several ways:
- Suspension: Smaller particles like silt and clay can be suspended within the water column and carried by the wave motion.
- Saltation: Slightly larger particles like sand bounce along the seabed due to the wave's energy.
- Traction: Larger sediments like pebbles and gravel are rolled or dragged along the seabed.
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Longshore Transport (Littoral Drift): This is a key mechanism for sediment transport along coastlines. When waves approach the shore at an angle, they create a current that flows parallel to the beach. This current, along with the swash and backwash of the waves, moves sediment along the beach in a zigzag pattern. If the waves were to come straight in, without an angle, there would be no longshore transport.
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Deposition: As waves lose energy, they deposit the sediment they are carrying. This typically occurs in areas where the wave energy decreases, such as in bays, behind headlands, or in deeper water offshore.
In Summary: Waves carry sediments through a continuous process of erosion, transportation, and deposition, driven by their energy and interaction with the coastline. The size and type of sediment that can be transported depend on the wave's energy and the water's velocity. Longshore transport is a significant process responsible for moving large volumes of sediment along coastlines.
