sand spit, bar, tombolo

Question 1

What are sandspits?

Answer 1

sand spits are low ridges of sand or shingle slowly extended from the shore across a bay or river estuary.

Question 2

What causes sand spits? (process)

Answer 2

the process of longshore drift

Question 3

Explain the process of longshore drift

Answer 3

A lateral movement caused when waves, driven by the prevailing wind, push material up the beach at an angle. This is called swash. Then, the returning backwash is dragged back by gravity down the beach at right angles. (this allows for deposition)

Question 4

Where do spits form and why?

Answer 4

Spits form where the coastline changes direction. This allows for material to be deposited in open water because there is now a sheltered area for deposition

Question 5

What happens as longshore drift continues to transport sediment and deposit it?

Answer 5

material builds up over time and appears above water level, continuing to grow longer and wider, giving the appearance than the beach has been extended

Question 6

The spit can continue to develop as long as…

Answer 6

the supply of deposits is greater than the amount of erosion

Question 7

As the sandspit becomes longer, the rate of its growth decreases because…

Answer 7

the water gets deeper

or the width of the channel is decreased, so the currents are faster

Question 8

Over time, the spit changes shape, to what and why

Answer 8

to be hooked at the end, in response to a temporary change in wind direction

Question 9

What develops in the low energy sheltered area behind the spit

Answer 9

a salt marsh

Question 10

WHAT DO YOU ADD ON THE END OF THE FORMATION OF A SPIT TO EXPLAIN THE FORMATION OF A TOMBOLO

Answer 10

a tombolo occurs when longshore drift continues, the same way as a sandspit, past the turning point of the coastline, and connects the mainland to an offshore island.
An example of a tombolo is at Chesil Beach

Question 11

WHAT DO YOU ADD TO THE FORMATION OF A SANDSPIT TO EXPLAIN THE FORMATION OF A BAR?

Answer 11

A bar forms when longshore drift continues in a straight line across a bay.
The coastline has an inland bend but as long as there is material supplied, longshore drift continues to deposit, from one headland to another, connecting the two and cutting straight across the bay.
A lagoon is formed behind the bay, which is an area of water, dammed by the bar in the bay.
An example of a sandbar is the Jupiter Sandbar

Question 12

Example of a tombolo

Answer 12

at Chesil Beach

Question 13

Example of a Bar

Answer 13

Jupiter Sandbar

Question 14

What does a coastline where a bar may form have?

Answer 14

An inland bend

Question 15

What forms behind sandbar?

Answer 15

A lagoon, an area of dammed water in the bay

Question 16

EXPLAIN FULLY THE FORMATION OF A SANDSPIT

Answer 16

Sand spits are low ridges of sand or shingle slowly extended from the shore across a bay or river estruary.
A sandspit is caused by the depositional process of longshore drift. This lateral movement is caused when waves, driven by the prevailing wind, push material up the beach at an angle, this is called swash. The returning backwash is then dragged back down the beach at right angles.
Spits form where the coastline changes direction, this allows for material to be deposited in open water, because there is a sheltered area for deposition.
As longshore drift continues to transport sediment and deposit it, material builds up and appears above water level, containing to grow longer and wider. This gives the appearance that the beach has been extended.
The spit can continue to develop as long as the amount of deposition exceeds the amount of erosion.
As the sandspit grows longer, the rate of its growth decreases either due to the water being deeper or channels width being reduced, meaning more erosion from faster currents.
The shape of a spit can change overtime to become hooked at the end, in response to a temporary change in wind direction and currents. A salt marsh may develop in the sheltered, low energy area behind a spit.