Sophie Duncan shows how to find out what soil is made of
Exploring the soil in your school grounds makes an interesting activity that pupils can repeat at home. In this experiment they can find out what soil is made of, and compare different types.
Collect a selection of soil samples. Make sure one is from under fallen leaves, and another is from an area where there is little vegetation. Take some clay and sand to make comparisons with your soil samples.
Fill a jam jar three-quarters full of water, and add soil until the jar is almost full. Put the lid on and shake it. Leave the jar on a table while the soil settles. Ask pupils to make observations of what they see, noting the time that has elapsed since the jar was shaken.
At regular intervals, mark on the jar the top of the layer of soil that has settled. Repeat the experiment using your different soil samples, and the clay and sand. Label each jar and make a note of the time it takes for the water to clear.
Initially, the water looks muddy. Stones in the soil settle at the bottom quite quickly. Over the next few minutes the larger particles settle, but the water still looks muddy. Over time the smaller sand particles settle, too, leaving the smallest clay particles and plant material floating in the water. After a few hours the clay particles and other material settle, leaving the water clear.
This helps pupils see how soil is made of different particles. Explain that some particles come from rocks that have been weathered or damaged by rivers, and some from animal and plant matter that has been broken down, and that these processes take a long time. Samples of soil collected where there is little vegetation will have more rock material and less plant matter than the samples collected from under leaves.