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Writing Task 1 Models
Sand dune formation

Sand dune formation (Process diagram)

The task

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The diagrams below show how sand dunes are formed.

Diagram showing the formation of sand dunes

Model answer

The diagrams illustrate the stages that are involved in the process of sand dune formation.

It is clear that the formation of sand dunes is a simple mechanism comprising three main stages. It requires the presence of wet grounds, as well as winds that blow in a particular direction.

The first necessary condition is wind: it must blow at an oblique angle towards the ground. This way, sand particles picked up by the wind will hit the ground. If the ground is dry, they will bounce off the surface. However, if there is an area of wet ground, many of these particles will be held down, become damp, and pile up.

Gradually, if the conditions persist, sand grains will start accumulating on top of the emerging pile. As this pile contains wet sand, it catches more particles and is unlikely to collapse. Over time, the pile becomes larger and larger and becomes what we call a dune.

(157 words)