Spits, bars, barrier islands and tombolo

What is a spit

• A long narrow beach of sand or shingle, it is attached to coastline and extends into sea or estuary

• Form on drift aligned beaches

What is a simple spit, compound spit and recurved spit

1. Linear spit

2. Curved spit that has wide recurved distal end with series of ‘barbs’ along spit

3. Curved or hooked end due changing wind or wave direction

What is distal and proximal point

1. Point in which spit connected to mainland

2. Furthest point from headland

How does a spit form

1. Longshore drift transports sediment along the coastline.

2. The coastline changes direction or reaches an estuary.

3. Wave energy decreases, so sediment is deposited.

4. Deposition continues out into the sea, forming a narrow ridge of sand or shingle attached to the land at one end.

5. The spit grows further due to continued longshore drift.

6. Changes in wind direction or wave direction may curve the end, creating a recurved end.

7. Sheltered water behind the spit becomes low energy, allowing mud and salt marshes to develop

How does a tombolo form

1. Longshore drift transports sediment along the coast.

2. Wave refraction creates a low-energy zone between the island and mainland.

3. Sediment is deposited in this sheltered area.

4. Deposition builds until the island connects to the mainland, forming a tombolo

How does a bar form

1. Longshore drift transports sediment which accumulates across bay where no strong flow of water

2. Bay becomes cut off to sea by sediment the bar which is sometimes not visible at high tides

3. A lagoon can form behind bar

What is the offshore bar theory

1. Waves deposit sediment offshore.

2. Sand bars build up above sea level.

3. Vegetation stabilises the sediment.

4. Barrier islands form parallel to the coast.

What is the spit accretion theory

1. Longshore drift forms a spit.

2. Sea level rises and breaks the spit from the mainland.

3. Water separates the spit from the coast.

4. A barrier island forms offshore.