Sand is spread mainly by waves and currents along coasts after being deposited there by rivers.
The Role of Water in Spreading Sand
Over vast stretches of time, rivers play a crucial role in the initial delivery of sand to coastal areas. As stated in the reference, over thousands and thousands of years, the shifting paths of rivers carry and drop off significant piles of sand near the coast. This deposited sand then becomes available for further distribution by the powerful forces of the ocean.
How Waves and Currents Distribute Sand
Once sand is deposited on the coast, the dynamic action of the sea takes over. The reference highlights that the sand is then spread by waves and currents.
- Waves: The rhythmic motion of waves crashing onto the shore and receding moves sand particles back and forth and along the beach face. This constant churning and transportation action helps to level out deposits and shape the beach profile.
- Currents: Longshore currents, which flow parallel to the coastline, are particularly effective at moving large quantities of sand over significant distances. These currents, driven by waves hitting the shore at an angle, transport sand along the coast, redistributing it and contributing to the formation of smooth, extensive sandy beaches.
Together, waves and currents work in tandem to take the sand delivered by rivers and sculpt it into the familiar smooth surfaces of sandy beaches that we see today.
