Observing Soil Differences
If you did the activity, Dig a Hole, you’ve probably noticed that soil changes a bit as you dig deeper. But, have you wondered if the soil changes as you travel around your local area?
Observing Soil Jars
empty jars ( 1kg peanut butter jars are ideal)
permanent felt pen
Visit different locations around the area – for example, your front lawn, an area under construction, a stream or river bank, the top of a hill or an area of native forest. Don’t use soil from a vegetable garden because this is often modified by adding compost. (If you are doing this as a classroom activity, ask students to bring in soil from different locations as part of their homework.)
Use the hand trowel to dig into the soil. Keep the hole narrow but dig down deep so you get a combination of topsoil and the soil below.
Put the soil in the jar until it is about half full.
Write the location on the jar lid with a felt.
Fill the jar with water. Shake it well and leave the jar to sit until the soil is settle and the water is mostly clear.
Put the jars holding the different soils next to each other. Observe the contents.
Can you see the differences in the layers in the soil? The heavier sand particles settle to the bottom first. Often a layer of clay particles rests on top of the sand. There may also be a layer of organic matter in the soil – or floating on the top of the water.
Can you see different colours in the soil layers? Are some of the layers lighter or darker than the others?
Can you explain any of the changes? For example, soil from a building site might actually be subsoil dug from deep foundations. Soils along rivers or streams are often sandy.
Observing Road Cuttings
a camera, or cell phone with camera
access to the internet
Go for a drive along back roads to check out road cuttings – places where the road has been carved out of a hilly area.
If it is safe, get out of the car to look at the cuttings. You can often see different layers.
Take photos of road cuttings. Compare photos from different locations.
If navigating the internet is easier than navigating the back roads, go on a virtual journey instead. Soils in the New Zealand Landscape – The Living Mantle, is an outstanding book on New Zealand soils. The NZSSS website has links to electronic chapters. These chapters have beautiful images of road cuttings throughout New Zealand.
Observing Soil Maps
Look at maps and images on the two websites.
Thing about the geology associated with these soils. For example, how do features like the Southern Alps or North Island volcanoes influence the soils in their vicinity? (The article Soils – Similar but Different has information about soil formation.)