Look at Diagram Q2 - Scottish Highers Geography - Question 2 - 2019

Sand spits are formed by the process of longshore drift. This process occurs when waves, driven by prevailing winds, push sediment along the beach in a zigzag pattern. As the waves approach the shore at an angle, the incoming water carries sand and pebbles up the beach.

1. Longshore Drift: As waves break at an angle to the coastline, the swash (the movement of water up the beach) carries sand in the same direction as the waves. The backwash returns water straight back down the beach due to gravity. Over time, this results in a net movement of sand along the coast.

2. Formation of Spits: If the coastline changes direction, the sand continues to be deposited in a secluded area, forming a spit. This is where the supply of sand exceeds the rate of erosion and allows sediment to build up over time. The spit may curve further into the water due to changes in wind direction or wave action.

3. Stabilization: The spit can become stabilized by vegetation, which further helps in trapping more sand, allowing for the formation of a distinct landform. This can result in a sheltered area behind the spit, which may develop into a lagoon.

Thus, the formation of a sand spit is a dynamic process influenced primarily by wave action and sediment deposition.