I agree we need to do an investigation. The suggestion is that the desert sand might have come from the soil. Let’s see if we can find sand in the soil around us. Before we do this lets think about soil, the soil in your garden. What do you think it is made of? Maybe it is just made of soil? Maybe it is made of a mixture of things? Let’s investigate these questions.
Collect some soil. Get a plastic transparent beaker or a jar with a lid. Put a couple of small spoonfuls of your soil into the container. Add enough water so that it is half full. Cover and shake for about 20 seconds. Put it down and wait for about fifteen minutes. Now look at it and make notes on what you see. Repeat with another sample and another beaker or container (investigations always need to be checked).
Has your experiment resulted in layers of stuff in the beaker? Maybe a bit like the layers in the image below.
If it has then think about why you have layers? What has formed the first layer and why? Was it because it was the lightest or heaviest ‘stuff ‘ in the jar (soil)? Is the second layer made up of ‘stuff’ that is lighter or heavier?
The bottom layer is ‘sand’ …..the heaviest ‘stuff’ that makes up soil. The other layers are ‘silt’ and ‘clay’. Look at the diagram that my friends have given you the sand particles are the biggest.
Now to deserts. In very arid (dry) conditions the soil dries out. The wind basically blows away the smallest particles of clay and silt leaving the largest so a desert of sand is formed.
Elizabeth … thank you for your question.