Coastal Environment - Spits, Bars and Tombolos

A set of revision cards describing the formation of spits, bars and tombolos.

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Formation of Spits

A spit is a ridge of sand or shingle that has been deposited in an area of low energy.

The sand would have originally been taken from a beach along the coastline, and, thanks to longshore drift, has travelled down the coast to this area.

When the sand reaches the area of low energy, it is deposited by the waves. Over time, this repeated process results in a complete spit.

Remember: a spit juts out to sea, but cannot join two piece of land because the current is too strong to allow it to form like this. The end of the spit is washed away before it can form a bar (see next page).

Keep in mind the order of processes required for these formations. You will need them on the following pages;

EROSION/WEATHERING ---> TRANSPORTATION ---> DEPOSITION.

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Formation of Bars

A bar is formed in the same way as a spit, only it joins two pieces of land together.

This happens because instead of being deposited out to sea or in the mouth of an estuary, a bar is formed in front of a bay or a cove. This is important because it means that there is no current that washes the end of the bar away before it can form.

The formation of a bar also leads to another landform - a lagoon. This is because it has separated one area of water from the sea, and so this has no current or wave formation. Instead, it becomes a lagoon.

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Formation of Tombolos

A tombolo is very similar to a bar. The only way in which they differ is the location in which they form.

While a bar forms in front of coves and bays, a tombolo forms between an island and the mainland. The shingle is deposited in an area of low energy behind the island, and eventually this forms a tombolo - which means the land is joined to the island by this shingle.

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